On Tue, Jan 12, 2021 at 10:20 PM Bill Wendling <morbo@xxxxxxxxxx> wrote: > > From: Sami Tolvanen <samitolvanen@xxxxxxxxxx> > > Enable the use of clang's Profile-Guided Optimization[1]. To generate a > profile, the kernel is instrumented with PGO counters, a representative > workload is run, and the raw profile data is collected from > /sys/kernel/debug/pgo/profraw. > > The raw profile data must be processed by clang's "llvm-profdata" tool > before it can be used during recompilation: > > $ cp /sys/kernel/debug/pgo/profraw vmlinux.profraw > $ llvm-profdata merge --output=vmlinux.profdata vmlinux.profraw > > Multiple raw profiles may be merged during this step. > > The data can now be used by the compiler: > > $ make LLVM=1 KCFLAGS=-fprofile-use=vmlinux.profdata ... > > This initial submission is restricted to x86, as that's the platform we > know works. This restriction can be lifted once other platforms have > been verified to work with PGO. > > Note that this method of profiling the kernel is clang-native, unlike > the clang support in kernel/gcov. > > [1] https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization > > Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> > Co-developed-by: Bill Wendling <morbo@xxxxxxxxxx> > Signed-off-by: Bill Wendling <morbo@xxxxxxxxxx> > Change-Id: Ic78e69c682286d3a44c4549a0138578c98138b77 > --- > v2: - Added "__llvm_profile_instrument_memop" based on Nathan Chancellor's > testing. > - Corrected documentation, re PGO flags when using LTO, based on Fangrui > Song's comments. > v3: - Added change log section based on Sedat Dilek's comments. > v4: - Remove non-x86 Makfile changes and se "hweight64" instead of using our > own popcount implementation, based on Nick Desaulniers's comment. > --- > Documentation/dev-tools/index.rst | 1 + > Documentation/dev-tools/pgo.rst | 127 +++++++++ > MAINTAINERS | 9 + > Makefile | 3 + > arch/Kconfig | 1 + > arch/x86/Kconfig | 1 + > arch/x86/boot/Makefile | 1 + > arch/x86/boot/compressed/Makefile | 1 + > arch/x86/entry/vdso/Makefile | 1 + > arch/x86/kernel/vmlinux.lds.S | 2 + > arch/x86/platform/efi/Makefile | 1 + > arch/x86/purgatory/Makefile | 1 + > arch/x86/realmode/rm/Makefile | 1 + > arch/x86/um/vdso/Makefile | 1 + > drivers/firmware/efi/libstub/Makefile | 1 + > include/asm-generic/vmlinux.lds.h | 44 +++ > kernel/Makefile | 1 + > kernel/pgo/Kconfig | 34 +++ > kernel/pgo/Makefile | 5 + > kernel/pgo/fs.c | 382 ++++++++++++++++++++++++++ > kernel/pgo/instrument.c | 185 +++++++++++++ > kernel/pgo/pgo.h | 206 ++++++++++++++ > scripts/Makefile.lib | 10 + > 23 files changed, 1019 insertions(+) > create mode 100644 Documentation/dev-tools/pgo.rst > create mode 100644 kernel/pgo/Kconfig > create mode 100644 kernel/pgo/Makefile > create mode 100644 kernel/pgo/fs.c > create mode 100644 kernel/pgo/instrument.c > create mode 100644 kernel/pgo/pgo.h > > diff --git a/Documentation/dev-tools/index.rst b/Documentation/dev-tools/index.rst > index f7809c7b1ba9e..8d6418e858062 100644 > --- a/Documentation/dev-tools/index.rst > +++ b/Documentation/dev-tools/index.rst > @@ -26,6 +26,7 @@ whole; patches welcome! > kgdb > kselftest > kunit/index > + pgo > > > .. only:: subproject and html > diff --git a/Documentation/dev-tools/pgo.rst b/Documentation/dev-tools/pgo.rst > new file mode 100644 > index 0000000000000..b7f11d8405b73 > --- /dev/null > +++ b/Documentation/dev-tools/pgo.rst > @@ -0,0 +1,127 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +=============================== > +Using PGO with the Linux kernel > +=============================== > + > +Clang's profiling kernel support (PGO_) enables profiling of the Linux kernel > +when building with Clang. The profiling data is exported via the ``pgo`` > +debugfs directory. > + > +.. _PGO: https://clang.llvm.org/docs/UsersManual.html#profile-guided-optimization > + > + > +Preparation > +=========== > + > +Configure the kernel with: > + > +.. code-block:: make > + > + CONFIG_DEBUG_FS=y > + CONFIG_PGO_CLANG=y > + > +Note that kernels compiled with profiling flags will be significantly larger > +and run slower. > + > +Profiling data will only become accessible once debugfs has been mounted: > + > +.. code-block:: sh > + > + mount -t debugfs none /sys/kernel/debug > + > + > +Customization > +============= > + > +You can enable or disable profiling for individual file and directories by > +adding a line similar to the following to the respective kernel Makefile: > + > +- For a single file (e.g. main.o) > + > + .. code-block:: make > + > + PGO_PROFILE_main.o := y > + > +- For all files in one directory > + > + .. code-block:: make > + > + PGO_PROFILE := y > + > +To exclude files from being profiled use > + > + .. code-block:: make > + > + PGO_PROFILE_main.o := n > + > +and > + > + .. code-block:: make > + > + PGO_PROFILE := n > + > +Only files which are linked to the main kernel image or are compiled as kernel > +modules are supported by this mechanism. > + > + > +Files > +===== > + > +The PGO kernel support creates the following files in debugfs: > + > +``/sys/kernel/debug/pgo`` > + Parent directory for all PGO-related files. > + > +``/sys/kernel/debug/pgo/reset`` > + Global reset file: resets all coverage data to zero when written to. > + > +``/sys/kernel/debug/profraw`` > + The raw PGO data that must be processed with ``llvm_profdata``. > + > + > +Workflow > +======== > + > +The PGO kernel can be run on the host or test machines. The data though should > +be analyzed with Clang's tools from the same Clang version as the kernel was > +compiled. Clang's tolerant of version skew, but it's easier to use the same > +Clang version. > + > +The profiling data is useful for optimizing the kernel, analyzing coverage, > +etc. Clang offers tools to perform these tasks. > + > +Here is an example workflow for profiling an instrumented kernel with PGO and > +using the result to optimize the kernel: > + > +1) Install the kernel on the TEST machine. > + > +2) Reset the data counters right before running the load tests > + > + .. code-block:: sh > + > + $ echo 1 > /sys/kernel/debug/pgo/reset Maybe I'm a noob, but I had to: $ mkdir -p /sys/kernel/debug $ mount -t debugfs none /sys/kernel/debug first. That might trip up future travelers (like myself, I'm prone to forget these unless they're in my shell history). > + > +3) Run the load tests. > + > +4) Collect the raw profile data > + > + .. code-block:: sh > + > + $ cp -a /sys/kernel/debug/pgo/profraw /tmp/vmlinux.profraw > + > +5) (Optional) Download the raw profile data to the HOST machine. > + > +6) Process the raw profile data > + > + .. code-block:: sh > + > + $ llvm-profdata merge --output=vmlinux.profdata vmlinux.profraw > + > + Note that multiple raw profile data files can be merged during this step. > + > +7) Rebuild the kernel using the profile data (PGO disabled) > + > + .. code-block:: sh > + > + $ make LLVM=1 KCFLAGS=-fprofile-use=vmlinux.profdata ... > diff --git a/MAINTAINERS b/MAINTAINERS > index cc1e6a5ee6e67..1b979da316fa4 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -13954,6 +13954,15 @@ S: Maintained > F: include/linux/personality.h > F: include/uapi/linux/personality.h > > +PGO BASED KERNEL PROFILING > +M: Sami Tolvanen <samitolvanen@xxxxxxxxxx> > +M: Bill Wendling <wcw@xxxxxxxxxx> > +R: Nathan Chancellor <natechancellor@xxxxxxxxx> > +R: Nick Desaulniers <ndesaulniers@xxxxxxxxxx> > +S: Supported > +F: Documentation/dev-tools/pgo.rst > +F: kernel/pgo > + > PHOENIX RC FLIGHT CONTROLLER ADAPTER > M: Marcus Folkesson <marcus.folkesson@xxxxxxxxx> > L: linux-input@xxxxxxxxxxxxxxx > diff --git a/Makefile b/Makefile > index 9e73f82e0d863..9128bfe1ccc97 100644 > --- a/Makefile > +++ b/Makefile > @@ -659,6 +659,9 @@ endif # KBUILD_EXTMOD > # Defaults to vmlinux, but the arch makefile usually adds further targets > all: vmlinux > > +CFLAGS_PGO_CLANG := -fprofile-generate > +export CFLAGS_PGO_CLANG > + > CFLAGS_GCOV := -fprofile-arcs -ftest-coverage \ > $(call cc-option,-fno-tree-loop-im) \ > $(call cc-disable-warning,maybe-uninitialized,) > diff --git a/arch/Kconfig b/arch/Kconfig > index 24862d15f3a36..f39d3991f6bfe 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -1112,6 +1112,7 @@ config ARCH_SPLIT_ARG64 > pairs of 32-bit arguments, select this option. > > source "kernel/gcov/Kconfig" > +source "kernel/pgo/Kconfig" > > source "scripts/gcc-plugins/Kconfig" > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index 21f851179ff08..36305ea61dc09 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -96,6 +96,7 @@ config X86 > select ARCH_SUPPORTS_DEBUG_PAGEALLOC > select ARCH_SUPPORTS_NUMA_BALANCING if X86_64 > select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <= 4096 > + select ARCH_SUPPORTS_PGO_CLANG if X86_64 > select ARCH_USE_BUILTIN_BSWAP > select ARCH_USE_QUEUED_RWLOCKS > select ARCH_USE_QUEUED_SPINLOCKS > diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile > index fe605205b4ce2..383853e32f673 100644 > --- a/arch/x86/boot/Makefile > +++ b/arch/x86/boot/Makefile > @@ -71,6 +71,7 @@ KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ > KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) > KBUILD_CFLAGS += -fno-asynchronous-unwind-tables > GCOV_PROFILE := n > +PGO_PROFILE := n > UBSAN_SANITIZE := n > > $(obj)/bzImage: asflags-y := $(SVGA_MODE) > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile > index e0bc3988c3faa..ed12ab65f6065 100644 > --- a/arch/x86/boot/compressed/Makefile > +++ b/arch/x86/boot/compressed/Makefile > @@ -54,6 +54,7 @@ CFLAGS_sev-es.o += -I$(objtree)/arch/x86/lib/ > > KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ > GCOV_PROFILE := n > +PGO_PROFILE := n > UBSAN_SANITIZE :=n > > KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE) > diff --git a/arch/x86/entry/vdso/Makefile b/arch/x86/entry/vdso/Makefile > index 02e3e42f380bd..26e2b3af0145c 100644 > --- a/arch/x86/entry/vdso/Makefile > +++ b/arch/x86/entry/vdso/Makefile > @@ -179,6 +179,7 @@ quiet_cmd_vdso = VDSO $@ > VDSO_LDFLAGS = -shared --hash-style=both --build-id=sha1 \ > $(call ld-option, --eh-frame-hdr) -Bsymbolic > GCOV_PROFILE := n > +PGO_PROFILE := n > > quiet_cmd_vdso_and_check = VDSO $@ > cmd_vdso_and_check = $(cmd_vdso); $(cmd_vdso_check) > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > index efd9e9ea17f25..f6cab2316c46a 100644 > --- a/arch/x86/kernel/vmlinux.lds.S > +++ b/arch/x86/kernel/vmlinux.lds.S > @@ -184,6 +184,8 @@ SECTIONS > > BUG_TABLE > > + PGO_CLANG_DATA > + > ORC_UNWIND_TABLE > > . = ALIGN(PAGE_SIZE); > diff --git a/arch/x86/platform/efi/Makefile b/arch/x86/platform/efi/Makefile > index 84b09c230cbd5..5f22b31446ad4 100644 > --- a/arch/x86/platform/efi/Makefile > +++ b/arch/x86/platform/efi/Makefile > @@ -2,6 +2,7 @@ > OBJECT_FILES_NON_STANDARD_efi_thunk_$(BITS).o := y > KASAN_SANITIZE := n > GCOV_PROFILE := n > +PGO_PROFILE := n > > obj-$(CONFIG_EFI) += quirks.o efi.o efi_$(BITS).o efi_stub_$(BITS).o > obj-$(CONFIG_EFI_MIXED) += efi_thunk_$(BITS).o > diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile > index 95ea17a9d20cb..36f20e99da0bc 100644 > --- a/arch/x86/purgatory/Makefile > +++ b/arch/x86/purgatory/Makefile > @@ -23,6 +23,7 @@ targets += purgatory.ro purgatory.chk > > # Sanitizer, etc. runtimes are unavailable and cannot be linked here. > GCOV_PROFILE := n > +PGO_PROFILE := n > KASAN_SANITIZE := n > UBSAN_SANITIZE := n > KCSAN_SANITIZE := n > diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile > index 83f1b6a56449f..21797192f958f 100644 > --- a/arch/x86/realmode/rm/Makefile > +++ b/arch/x86/realmode/rm/Makefile > @@ -76,4 +76,5 @@ KBUILD_CFLAGS := $(REALMODE_CFLAGS) -D_SETUP -D_WAKEUP \ > KBUILD_AFLAGS := $(KBUILD_CFLAGS) -D__ASSEMBLY__ > KBUILD_CFLAGS += -fno-asynchronous-unwind-tables > GCOV_PROFILE := n > +PGO_PROFILE := n > UBSAN_SANITIZE := n > diff --git a/arch/x86/um/vdso/Makefile b/arch/x86/um/vdso/Makefile > index 5943387e3f357..54f5768f58530 100644 > --- a/arch/x86/um/vdso/Makefile > +++ b/arch/x86/um/vdso/Makefile > @@ -64,6 +64,7 @@ quiet_cmd_vdso = VDSO $@ > > VDSO_LDFLAGS = -fPIC -shared -Wl,--hash-style=sysv > GCOV_PROFILE := n > +PGO_PROFILE := n > > # > # Install the unstripped copy of vdso*.so listed in $(vdso-install-y). > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile > index 8a94388e38b33..2d81623b33f29 100644 > --- a/drivers/firmware/efi/libstub/Makefile > +++ b/drivers/firmware/efi/libstub/Makefile > @@ -40,6 +40,7 @@ KBUILD_CFLAGS := $(cflags-y) -Os -DDISABLE_BRANCH_PROFILING \ > KBUILD_CFLAGS := $(filter-out $(CC_FLAGS_SCS), $(KBUILD_CFLAGS)) > > GCOV_PROFILE := n > +PGO_PROFILE := n > # Sanitizer runtimes are unavailable and cannot be linked here. > KASAN_SANITIZE := n > KCSAN_SANITIZE := n > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index b2b3d81b1535a..3a591bb18c5fb 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -316,6 +316,49 @@ > #define THERMAL_TABLE(name) > #endif > > +#ifdef CONFIG_PGO_CLANG > +#define PGO_CLANG_DATA \ > + __llvm_prf_data : AT(ADDR(__llvm_prf_data) - LOAD_OFFSET) { \ > + . = ALIGN(8); \ > + __llvm_prf_start = .; \ > + __llvm_prf_data_start = .; \ > + KEEP(*(__llvm_prf_data)) \ > + . = ALIGN(8); \ > + __llvm_prf_data_end = .; \ > + } \ So if I do a build of $ make CC=clang I observe the following error: `.discard.text' referenced in section `__llvm_prf_data' of arch/x86/kernel/setup.o: defined in discarded section `.discard.text' of arch/x86/kernel/setup.o `.discard.text' referenced in section `__llvm_prf_data' of arch/x86/mm/init.o: defined in discarded section `.discard.text' of arch/x86/mm/init.o This can be investigated more via: $ llvm-objdump -Dr -j __llvm_prf_data arch/x86/mm/init.o | grep discard 0000000000000168: R_X86_64_64 .discard.text So looks like a relocation is referencing something in .discard.text. $ llvm-objdump -Dr -j .discard.text arch/x86/mm/init.o ... 0000000000000000 <__brk_reservation_fn_early_pgt_alloc__>: 0: 48 83 05 00 00 00 00 01 addq $1, (%rip) # 8 <__brk_reservation_fn_early_pgt_alloc__+0x8> 0000000000000003: R_X86_64_PC32 __llvm_prf_cnts+0xf3 8: c3 retq Looks like arch/x86/include/asm/setup.h defines the macro RESERVE_BRK which defines a static function in the .discard.text section. Is there a function attribute that we can use to say "please don't profile this one function?" For arch/x86/kernel/setup.o it looks like the same issue with __brk_reservation_fn_dmi_alloc__. More specifically, this warning goes away when using LLD: $ make CC=clang LD=ld.lld Not sure yet why these warnings are only observed when using BFD? Maybe LLD should also be producing this diagnostic, but is not? Anyways, I was able to build+boot profiling mode binaries built with: $ make LLVM=1 defconfig+PGO $ make LLVM=1 LLVM_IAS=1 defconfig+PGO It would be good to resolve/investigate the above error with BFD and fix it, or make this config also depend on LLD for now. ie. $ make CC=clang defconfig+PGO I'm going to try rebuilding+booting with the profile data now, and will report back. > + __llvm_prf_cnts : AT(ADDR(__llvm_prf_cnts) - LOAD_OFFSET) { \ > + . = ALIGN(8); \ > + __llvm_prf_cnts_start = .; \ > + KEEP(*(__llvm_prf_cnts)) \ > + . = ALIGN(8); \ > + __llvm_prf_cnts_end = .; \ > + } \ > + __llvm_prf_names : AT(ADDR(__llvm_prf_names) - LOAD_OFFSET) { \ > + . = ALIGN(8); \ > + __llvm_prf_names_start = .; \ > + KEEP(*(__llvm_prf_names)) \ > + . = ALIGN(8); \ > + __llvm_prf_names_end = .; \ > + . = ALIGN(8); \ > + } \ > + __llvm_prf_vals : AT(ADDR(__llvm_prf_vals) - LOAD_OFFSET) { \ > + __llvm_prf_vals_start = .; \ > + KEEP(*(__llvm_prf_vals)) \ > + . = ALIGN(8); \ > + __llvm_prf_vals_end = .; \ > + . = ALIGN(8); \ > + } \ > + __llvm_prf_vnds : AT(ADDR(__llvm_prf_vnds) - LOAD_OFFSET) { \ > + __llvm_prf_vnds_start = .; \ > + KEEP(*(__llvm_prf_vnds)) \ > + . = ALIGN(8); \ > + __llvm_prf_vnds_end = .; \ > + __llvm_prf_end = .; \ > + } > +#else > +#define PGO_CLANG_DATA > +#endif > + > #define KERNEL_DTB() \ > STRUCT_ALIGN(); \ > __dtb_start = .; \ > @@ -1125,6 +1168,7 @@ > CONSTRUCTORS \ > } \ > BUG_TABLE \ > + PGO_CLANG_DATA > > #define INIT_TEXT_SECTION(inittext_align) \ > . = ALIGN(inittext_align); \ > diff --git a/kernel/Makefile b/kernel/Makefile > index aa7368c7eabf3..0b34ca228ba46 100644 > --- a/kernel/Makefile > +++ b/kernel/Makefile > @@ -111,6 +111,7 @@ obj-$(CONFIG_BPF) += bpf/ > obj-$(CONFIG_KCSAN) += kcsan/ > obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o > obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call.o > +obj-$(CONFIG_PGO_CLANG) += pgo/ > > obj-$(CONFIG_PERF_EVENTS) += events/ > > diff --git a/kernel/pgo/Kconfig b/kernel/pgo/Kconfig > new file mode 100644 > index 0000000000000..318d36bb3d106 > --- /dev/null > +++ b/kernel/pgo/Kconfig > @@ -0,0 +1,34 @@ > +# SPDX-License-Identifier: GPL-2.0-only > +menu "Profile Guided Optimization (PGO) (EXPERIMENTAL)" > + > +config ARCH_SUPPORTS_PGO_CLANG > + bool > + > +config PGO_CLANG > + bool "Enable clang's PGO-based kernel profiling" > + depends on DEBUG_FS > + depends on ARCH_SUPPORTS_PGO_CLANG probably should additionally: depends on CLANG_VERSION >= 120000 I'm observing the same failed assertion as Nathan trying to build x86_64 defconfig (drivers/gpu/drm/i915/i915_query.c), that should be fixed by: https://reviews.llvm.org/D94470 I think that would also help prevent this config from being selectable if not using CC=clang? > + help > + This option enables clang's PGO (Profile Guided Optimization) based > + code profiling to better optimize the kernel. > + > + If unsure, say N. > + > + Run a representative workload for your application on a kernel > + compiled with this option and download the raw profile file from > + /sys/kernel/debug/pgo/profraw. This file needs to be processed with > + llvm-profdata. It may be merged with other collected raw profiles. > + > + Copy the resulting profile file into vmlinux.profdata, and enable > + KCFLAGS=-fprofile-use=vmlinux.profdata to produce an optimized > + kernel. > + > + Note that a kernel compiled with profiling flags will be > + significatnly larger and run slower. Also be sure to exclude files ^ typo: significantly > + from profiling which are not linked to the kernel image to prevent > + linker errors. > + > + Note that the debugfs filesystem has to be mounted to access > + profiling data. > + > +endmenu > diff --git a/kernel/pgo/Makefile b/kernel/pgo/Makefile > new file mode 100644 > index 0000000000000..41e27cefd9a47 > --- /dev/null > +++ b/kernel/pgo/Makefile > @@ -0,0 +1,5 @@ > +# SPDX-License-Identifier: GPL-2.0 > +GCOV_PROFILE := n > +PGO_PROFILE := n > + > +obj-y += fs.o instrument.o > diff --git a/kernel/pgo/fs.c b/kernel/pgo/fs.c > new file mode 100644 > index 0000000000000..790a8df037bfc > --- /dev/null > +++ b/kernel/pgo/fs.c > @@ -0,0 +1,382 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) 2019 Google, Inc. > + * > + * Author: > + * Sami Tolvanen <samitolvanen@xxxxxxxxxx> > + * > + * This software is licensed under the terms of the GNU General Public > + * License version 2, as published by the Free Software Foundation, and > + * may be copied, distributed, and modified under those terms. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + */ > + > +#define pr_fmt(fmt) "pgo: " fmt > + > +#include <linux/kernel.h> > +#include <linux/debugfs.h> > +#include <linux/fs.h> > +#include <linux/module.h> > +#include <linux/slab.h> > +#include <linux/vmalloc.h> > +#include "pgo.h" > + > +static struct dentry *directory; > + > +struct prf_private_data { > + void *buffer; > + unsigned long size; > +}; > + > +/* > + * Raw profile data format: > + * > + * - llvm_prf_header > + * - __llvm_prf_data > + * - __llvm_prf_cnts > + * - __llvm_prf_names > + * - zero padding to 8 bytes > + * - for each llvm_prf_data in __llvm_prf_data: > + * - llvm_prf_value_data > + * - llvm_prf_value_record + site count array > + * - llvm_prf_value_node_data > + * ... > + * ... > + * ... > + */ > + > +static void prf_fill_header(void **buffer) > +{ > + struct llvm_prf_header *header = *(struct llvm_prf_header **)buffer; > + > + header->magic = LLVM_PRF_MAGIC; > + header->version = LLVM_PRF_VARIANT_MASK_IR | LLVM_PRF_VERSION; > + header->data_size = prf_data_count(); > + header->padding_bytes_before_counters = 0; > + header->counters_size = prf_cnts_count(); > + header->padding_bytes_after_counters = 0; > + header->names_size = prf_names_count(); > + header->counters_delta = (u64)__llvm_prf_cnts_start; > + header->names_delta = (u64)__llvm_prf_names_start; > + header->value_kind_last = LLVM_PRF_IPVK_LAST; > + > + *buffer += sizeof(*header); > +} > + > +/* > + * Copy the source into the buffer, incrementing the pointer into buffer in the > + * process. > + */ > +static void prf_copy_to_buffer(void **buffer, void *src, unsigned long size) > +{ > + memcpy(*buffer, src, size); > + *buffer += size; > +} > + > +static u32 __prf_get_value_size(struct llvm_prf_data *p, u32 *value_kinds) > +{ > + struct llvm_prf_value_node **nodes = > + (struct llvm_prf_value_node **)p->values; > + u32 kinds = 0; > + u32 size = 0; > + unsigned int kind; > + unsigned int n; > + unsigned int s = 0; > + > + for (kind = 0; kind < ARRAY_SIZE(p->num_value_sites); kind++) { > + unsigned int sites = p->num_value_sites[kind]; > + > + if (!sites) > + continue; > + > + /* Record + site count array */ > + size += prf_get_value_record_size(sites); > + kinds++; > + > + if (!nodes) > + continue; > + > + for (n = 0; n < sites; n++) { > + u32 count = 0; > + struct llvm_prf_value_node *site = nodes[s + n]; > + > + while (site && ++count <= U8_MAX) > + site = site->next; > + > + size += count * > + sizeof(struct llvm_prf_value_node_data); > + } > + > + s += sites; > + } > + > + if (size) > + size += sizeof(struct llvm_prf_value_data); > + > + if (value_kinds) > + *value_kinds = kinds; > + > + return size; > +} > + > +static u32 prf_get_value_size(void) > +{ > + u32 size = 0; > + struct llvm_prf_data *p; > + > + for (p = __llvm_prf_data_start; p < __llvm_prf_data_end; p++) > + size += __prf_get_value_size(p, NULL); > + > + return size; > +} > + > +/* Serialize the profiling's value. */ > +static void prf_serialize_value(struct llvm_prf_data *p, void **buffer) > +{ > + struct llvm_prf_value_data header; > + struct llvm_prf_value_node **nodes = > + (struct llvm_prf_value_node **)p->values; > + unsigned int kind; > + unsigned int n; > + unsigned int s = 0; > + > + header.total_size = __prf_get_value_size(p, &header.num_value_kinds); > + > + if (!header.num_value_kinds) > + /* Nothing to write. */ > + return; > + > + prf_copy_to_buffer(buffer, &header, sizeof(header)); > + > + for (kind = 0; kind < ARRAY_SIZE(p->num_value_sites); kind++) { > + struct llvm_prf_value_record *record; > + u8 *counts; > + unsigned int sites = p->num_value_sites[kind]; > + > + if (!sites) > + continue; > + > + /* Profiling value record. */ > + record = *(struct llvm_prf_value_record **)buffer; > + *buffer += prf_get_value_record_header_size(); > + > + record->kind = kind; > + record->num_value_sites = sites; > + > + /* Site count array. */ > + counts = *(u8 **)buffer; > + *buffer += prf_get_value_record_site_count_size(sites); > + > + /* > + * If we don't have nodes, we can skip updating the site count > + * array, because the buffer is zero filled. > + */ > + if (!nodes) > + continue; > + > + for (n = 0; n < sites; n++) { > + u32 count = 0; > + struct llvm_prf_value_node *site = nodes[s + n]; > + > + while (site && ++count <= U8_MAX) { > + prf_copy_to_buffer(buffer, site, > + sizeof(struct llvm_prf_value_node_data)); > + site = site->next; > + } > + > + counts[n] = (u8)count; > + } > + > + s += sites; > + } > +} > + > +static void prf_serialize_values(void **buffer) > +{ > + struct llvm_prf_data *p; > + > + for (p = __llvm_prf_data_start; p < __llvm_prf_data_end; p++) > + prf_serialize_value(p, buffer); > +} > + > +static inline unsigned long prf_get_padding(unsigned long size) > +{ > + return 8 - (size % 8); > +} > + > +static unsigned long prf_buffer_size(void) > +{ > + return sizeof(struct llvm_prf_header) + > + prf_data_size() + > + prf_cnts_size() + > + prf_names_size() + > + prf_get_padding(prf_names_size()) + > + prf_get_value_size(); > +} > + > +/* Serialize the profling data into a format LLVM's tools can understand. */ ^ typo: profiling > +static int prf_serialize(struct prf_private_data *p) > +{ > + int err = 0; > + void *buffer; > + > + p->size = prf_buffer_size(); > + p->buffer = vzalloc(p->size); > + > + if (!p->buffer) { > + err = -ENOMEM; > + goto out; > + } > + > + buffer = p->buffer; > + > + prf_fill_header(&buffer); > + prf_copy_to_buffer(&buffer, __llvm_prf_data_start, prf_data_size()); > + prf_copy_to_buffer(&buffer, __llvm_prf_cnts_start, prf_cnts_size()); > + prf_copy_to_buffer(&buffer, __llvm_prf_names_start, prf_names_size()); > + buffer += prf_get_padding(prf_names_size()); > + > + prf_serialize_values(&buffer); > + > +out: > + return err; > +} > + > +/* open() implementation for PGO. Creates a copy of the profiling data set. */ > +static int prf_open(struct inode *inode, struct file *file) > +{ > + struct prf_private_data *data; > + unsigned long flags; > + int err; > + > + data = kzalloc(sizeof(*data), GFP_KERNEL); > + if (!data) { > + err = -ENOMEM; > + goto out; > + } > + > + flags = prf_lock(); > + > + err = prf_serialize(data); > + if (err) { > + kfree(data); > + goto out_unlock; > + } > + > + file->private_data = data; > + > +out_unlock: > + prf_unlock(flags); > +out: > + return err; > +} > + > +/* read() implementation for PGO. */ > +static ssize_t prf_read(struct file *file, char __user *buf, size_t count, > + loff_t *ppos) > +{ > + struct prf_private_data *data = file->private_data; > + > + BUG_ON(!data); > + > + return simple_read_from_buffer(buf, count, ppos, data->buffer, > + data->size); > +} > + > +/* release() implementation for PGO. Release resources allocated by open(). */ > +static int prf_release(struct inode *inode, struct file *file) > +{ > + struct prf_private_data *data = file->private_data; > + > + if (data) { > + vfree(data->buffer); > + kfree(data); > + } > + > + return 0; > +} > + > +static const struct file_operations prf_fops = { > + .owner = THIS_MODULE, > + .open = prf_open, > + .read = prf_read, > + .llseek = default_llseek, > + .release = prf_release > +}; > + > +/* write() implementation for resetting PGO's profile data. */ > +static ssize_t reset_write(struct file *file, const char __user *addr, > + size_t len, loff_t *pos) > +{ > + struct llvm_prf_data *data; > + > + memset(__llvm_prf_cnts_start, 0, prf_cnts_size()); > + > + for (data = __llvm_prf_data_start; data < __llvm_prf_data_end; ++data) { > + struct llvm_prf_value_node **vnodes; > + u64 current_vsite_count; > + u32 i; > + > + if (!data->values) > + continue; > + > + current_vsite_count = 0; > + vnodes = (struct llvm_prf_value_node **)data->values; > + > + for (i = LLVM_PRF_IPVK_FIRST; i <= LLVM_PRF_IPVK_LAST; ++i) > + current_vsite_count += data->num_value_sites[i]; > + > + for (i = 0; i < current_vsite_count; ++i) { > + struct llvm_prf_value_node *current_vnode = vnodes[i]; > + > + while (current_vnode) { > + current_vnode->count = 0; > + current_vnode = current_vnode->next; > + } > + } > + } > + > + return len; > +} > + > +static const struct file_operations prf_reset_fops = { > + .owner = THIS_MODULE, > + .write = reset_write, > + .llseek = noop_llseek, > +}; > + > +/* Create debugfs entries. */ > +static int __init pgo_init(void) > +{ > + directory = debugfs_create_dir("pgo", NULL); > + if (!directory) > + goto err_remove; > + > + if (!debugfs_create_file("profraw", 0600, directory, NULL, > + &prf_fops)) > + goto err_remove; > + > + if (!debugfs_create_file("reset", 0200, directory, NULL, > + &prf_reset_fops)) > + goto err_remove; > + > + return 0; > + > +err_remove: > + pr_err("initialization failed\n"); > + return -EIO; > +} > + > +/* Remove debufs entries. */ ^ typo: debugfs > +static void __exit pgo_exit(void) > +{ > + debugfs_remove_recursive(directory); > +} > + > +module_init(pgo_init); > +module_exit(pgo_exit); > diff --git a/kernel/pgo/instrument.c b/kernel/pgo/instrument.c > new file mode 100644 > index 0000000000000..6084ff0652e85 > --- /dev/null > +++ b/kernel/pgo/instrument.c > @@ -0,0 +1,185 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) 2019 Google, Inc. > + * > + * Author: > + * Sami Tolvanen <samitolvanen@xxxxxxxxxx> > + * > + * This software is licensed under the terms of the GNU General Public > + * License version 2, as published by the Free Software Foundation, and > + * may be copied, distributed, and modified under those terms. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + */ > + > +#define pr_fmt(fmt) "pgo: " fmt > + > +#include <linux/bitops.h> > +#include <linux/kernel.h> > +#include <linux/export.h> > +#include <linux/spinlock.h> > +#include <linux/types.h> > +#include "pgo.h" > + > +/* Lock guarding value node access and serialization. */ > +static DEFINE_SPINLOCK(pgo_lock); > +static int current_node; > + > +unsigned long prf_lock(void) > +{ > + unsigned long flags; > + > + spin_lock_irqsave(&pgo_lock, flags); > + > + return flags; > +} > + > +void prf_unlock(unsigned long flags) > +{ > + spin_unlock_irqrestore(&pgo_lock, flags); > +} > + > +/* > + * Return a newly allocated profiling value node which contains the tracked > + * value by the value profiler. > + * Note: caller *must* hold pgo_lock. > + */ > +static struct llvm_prf_value_node *allocate_node(struct llvm_prf_data *p, > + u32 index, u64 value) > +{ > + if (&__llvm_prf_vnds_start[current_node + 1] >= __llvm_prf_vnds_end) > + return NULL; /* Out of nodes */ > + > + current_node++; > + > + /* Make sure the node is entirely within the section */ > + if (&__llvm_prf_vnds_start[current_node] >= __llvm_prf_vnds_end || > + &__llvm_prf_vnds_start[current_node + 1] > __llvm_prf_vnds_end) > + return NULL; > + > + return &__llvm_prf_vnds_start[current_node]; > +} > + > +/* > + * Counts the number of times a target value is seen. > + * > + * Records the target value for the CounterIndex if not seen before. Otherwise, > + * increments the counter associated w/ the target value. > + */ > +void __llvm_profile_instrument_target(u64 target_value, void *data, u32 index); > +void __llvm_profile_instrument_target(u64 target_value, void *data, u32 index) > +{ > + struct llvm_prf_data *p = (struct llvm_prf_data *)data; > + struct llvm_prf_value_node **counters; > + struct llvm_prf_value_node *curr; > + struct llvm_prf_value_node *min = NULL; > + struct llvm_prf_value_node *prev = NULL; > + u64 min_count = U64_MAX; > + u8 values = 0; > + unsigned long flags; > + > + if (!p || !p->values) > + return; > + > + counters = (struct llvm_prf_value_node **)p->values; > + curr = counters[index]; > + > + while (curr) { > + if (target_value == curr->value) { > + curr->count++; > + return; > + } > + > + if (curr->count < min_count) { > + min_count = curr->count; > + min = curr; > + } > + > + prev = curr; > + curr = curr->next; > + values++; > + } > + > + if (values >= LLVM_PRF_MAX_NUM_VALS_PER_SITE) { > + if (!min->count || !(--min->count)) { > + curr = min; > + curr->value = target_value; > + curr->count++; > + } > + return; > + } > + > + /* Lock when updating the value node structure. */ > + flags = prf_lock(); > + > + curr = allocate_node(p, index, target_value); > + if (!curr) > + goto out; > + > + curr->value = target_value; > + curr->count++; > + > + if (!counters[index]) > + counters[index] = curr; > + else if (prev && !prev->next) > + prev->next = curr; > + > +out: > + prf_unlock(flags); > +} > +EXPORT_SYMBOL(__llvm_profile_instrument_target); > + > +/* Counts the number of times a range of targets values are seen. */ > +void __llvm_profile_instrument_range(u64 target_value, void *data, > + u32 index, s64 precise_start, > + s64 precise_last, s64 large_value); > +void __llvm_profile_instrument_range(u64 target_value, void *data, > + u32 index, s64 precise_start, > + s64 precise_last, s64 large_value) > +{ > + if (large_value != S64_MIN && (s64)target_value >= large_value) > + target_value = large_value; > + else if ((s64)target_value < precise_start || > + (s64)target_value > precise_last) > + target_value = precise_last + 1; > + > + __llvm_profile_instrument_target(target_value, data, index); > +} > +EXPORT_SYMBOL(__llvm_profile_instrument_range); > + > +static u64 inst_prof_get_range_rep_value(u64 value) > +{ > + if (value <= 8) > + /* The first ranges are individually tracked, us it as is. */ > + return value; > + else if (value >= 513) > + /* The last range is mapped to its lowest value. */ > + return 513; > + else if (hweight64(value) == 1) > + /* If it's a power of two, use it as is. */ > + return value; > + > + /* Otherwise, take to the previous power of two + 1. */ > + return (1 << (64 - __builtin_clzll(value) - 1)) + 1; > +} > + > +/* > + * The target values are partitioned into multiple ranges. The range spec is > + * defined in compiler-rt/include/profile/InstrProfData.inc. > + */ > +void __llvm_profile_instrument_memop(u64 target_value, void *data, > + u32 counter_index); > +void __llvm_profile_instrument_memop(u64 target_value, void *data, > + u32 counter_index) > +{ > + u64 rep_value; > + > + /* Map the target value to the representative value of its range. */ > + rep_value = inst_prof_get_range_rep_value(target_value); > + __llvm_profile_instrument_target(rep_value, data, counter_index); > +} > +EXPORT_SYMBOL(__llvm_profile_instrument_memop); > diff --git a/kernel/pgo/pgo.h b/kernel/pgo/pgo.h > new file mode 100644 > index 0000000000000..df0aa278f28bd > --- /dev/null > +++ b/kernel/pgo/pgo.h > @@ -0,0 +1,206 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * Copyright (C) 2019 Google, Inc. > + * > + * Author: > + * Sami Tolvanen <samitolvanen@xxxxxxxxxx> > + * > + * This software is licensed under the terms of the GNU General Public > + * License version 2, as published by the Free Software Foundation, and > + * may be copied, distributed, and modified under those terms. > + * > + * This program is distributed in the hope that it will be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + */ > + > +#ifndef _PGO_H > +#define _PGO_H > + > +/* > + * Note: These internal LLVM definitions must match the compiler version. > + * See llvm/include/llvm/ProfileData/InstrProfData.inc in LLVM's source code. > + */ > + > +#ifdef CONFIG_64BIT > + #define LLVM_PRF_MAGIC \ > + ((u64)255 << 56 | \ > + (u64)'l' << 48 | \ > + (u64)'p' << 40 | \ > + (u64)'r' << 32 | \ > + (u64)'o' << 24 | \ > + (u64)'f' << 16 | \ > + (u64)'r' << 8 | \ > + (u64)129) > +#else > + #define LLVM_PRF_MAGIC \ > + ((u64)255 << 56 | \ > + (u64)'l' << 48 | \ > + (u64)'p' << 40 | \ > + (u64)'r' << 32 | \ > + (u64)'o' << 24 | \ > + (u64)'f' << 16 | \ > + (u64)'R' << 8 | \ > + (u64)129) > +#endif > + > +#define LLVM_PRF_VERSION 5 > +#define LLVM_PRF_DATA_ALIGN 8 > +#define LLVM_PRF_IPVK_FIRST 0 > +#define LLVM_PRF_IPVK_LAST 1 > +#define LLVM_PRF_MAX_NUM_VALS_PER_SITE 16 > + > +#define LLVM_PRF_VARIANT_MASK_IR (0x1ull << 56) > +#define LLVM_PRF_VARIANT_MASK_CSIR (0x1ull << 57) > + > +/** > + * struct llvm_prf_header - represents the raw profile header data structure. > + * @magic: the magic token for the file format. > + * @version: the version of the file format. > + * @data_size: the number of entries in the profile data section. > + * @padding_bytes_before_counters: the number of padding bytes before the > + * counters. > + * @counters_size: the size in bytes of the LLVM profile section containing the > + * counters. > + * @padding_bytes_after_counters: the number of padding bytes after the > + * counters. > + * @names_size: the size in bytes of the LLVM profile section containing the > + * counters' names. > + * @counters_delta: the beginning of the LLMV profile counters section. > + * @names_delta: the beginning of the LLMV profile names section. > + * @value_kind_last: the last profile value kind. > + */ > +struct llvm_prf_header { > + u64 magic; > + u64 version; > + u64 data_size; > + u64 padding_bytes_before_counters; > + u64 counters_size; > + u64 padding_bytes_after_counters; > + u64 names_size; > + u64 counters_delta; > + u64 names_delta; > + u64 value_kind_last; > +}; > + > +/** > + * struct llvm_prf_data - represents the per-function control structure. > + * @name_ref: the reference to the function's name. > + * @func_hash: the hash value of the function. > + * @counter_ptr: a pointer to the profile counter. > + * @function_ptr: a pointer to the function. > + * @values: the profiling values associated with this function. > + * @num_counters: the number of counters in the function. > + * @num_value_sites: the number of value profile sites. > + */ > +struct llvm_prf_data { > + const u64 name_ref; > + const u64 func_hash; > + const void *counter_ptr; > + const void *function_ptr; > + void *values; > + const u32 num_counters; > + const u16 num_value_sites[LLVM_PRF_IPVK_LAST + 1]; > +} __aligned(LLVM_PRF_DATA_ALIGN); > + > +/** > + * structure llvm_prf_value_node_data - represents the data part of the struct > + * llvm_prf_value_node data structure. > + * @value: the value counters. > + * @count: the counters' count. > + */ > +struct llvm_prf_value_node_data { > + u64 value; > + u64 count; > +}; > + > +/** > + * struct llvm_prf_value_node - represents an internal data structure used by > + * the value profiler. > + * @value: the value counters. > + * @count: the counters' count. > + * @next: the next value node. > + */ > +struct llvm_prf_value_node { > + u64 value; > + u64 count; > + struct llvm_prf_value_node *next; > +}; > + > +/** > + * struct llvm_prf_value_data - represents the value profiling data in indexed > + * format. > + * @total_size: the total size in bytes including this field. > + * @num_value_kinds: the number of value profile kinds that has value profile > + * data. > + */ > +struct llvm_prf_value_data { > + u32 total_size; > + u32 num_value_kinds; > +}; > + > +/** > + * struct llvm_prf_value_record - represents the on-disk layout of the value > + * profile data of a particular kind for one function. > + * @kind: the kind of the value profile record. > + * @num_value_sites: the number of value profile sites. > + * @site_count_array: the first element of the array that stores the number > + * of profiled values for each value site. > + */ > +struct llvm_prf_value_record { > + u32 kind; > + u32 num_value_sites; > + u8 site_count_array[]; > +}; > + > +#define prf_get_value_record_header_size() \ > + offsetof(struct llvm_prf_value_record, site_count_array) > +#define prf_get_value_record_site_count_size(sites) \ > + roundup((sites), 8) > +#define prf_get_value_record_size(sites) \ > + (prf_get_value_record_header_size() + \ > + prf_get_value_record_site_count_size((sites))) > + > +/* Data sections */ > +extern struct llvm_prf_data __llvm_prf_data_start[]; > +extern struct llvm_prf_data __llvm_prf_data_end[]; > + > +extern u64 __llvm_prf_cnts_start[]; > +extern u64 __llvm_prf_cnts_end[]; > + > +extern char __llvm_prf_names_start[]; > +extern char __llvm_prf_names_end[]; > + > +extern struct llvm_prf_value_node __llvm_prf_vnds_start[]; > +extern struct llvm_prf_value_node __llvm_prf_vnds_end[]; > + > +/* Locking for vnodes */ > +extern unsigned long prf_lock(void); > +extern void prf_unlock(unsigned long flags); > + > +#define __DEFINE_PRF_SIZE(s) \ > + static inline unsigned long prf_ ## s ## _size(void) \ > + { \ > + unsigned long start = \ > + (unsigned long)__llvm_prf_ ## s ## _start; \ > + unsigned long end = \ > + (unsigned long)__llvm_prf_ ## s ## _end; \ > + return roundup(end - start, \ > + sizeof(__llvm_prf_ ## s ## _start[0])); \ > + } \ > + static inline unsigned long prf_ ## s ## _count(void) \ > + { \ > + return prf_ ## s ## _size() / \ > + sizeof(__llvm_prf_ ## s ## _start[0]); \ > + } > + > +__DEFINE_PRF_SIZE(data); > +__DEFINE_PRF_SIZE(cnts); > +__DEFINE_PRF_SIZE(names); > +__DEFINE_PRF_SIZE(vnds); > + > +#undef __DEFINE_PRF_SIZE > + > +#endif /* _PGO_H */ > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib > index 213677a5ed33e..9b218afb5cb87 100644 > --- a/scripts/Makefile.lib > +++ b/scripts/Makefile.lib > @@ -143,6 +143,16 @@ _c_flags += $(if $(patsubst n%,, \ > $(CFLAGS_GCOV)) > endif > > +# > +# Enable clang's PGO profiling flags for a file or directory depending on > +# variables PGO_PROFILE_obj.o and PGO_PROFILE. > +# > +ifeq ($(CONFIG_PGO_CLANG),y) > +_c_flags += $(if $(patsubst n%,, \ > + $(PGO_PROFILE_$(basetarget).o)$(PGO_PROFILE)y), \ > + $(CFLAGS_PGO_CLANG)) > +endif > + > # > # Enable address sanitizer flags for kernel except some files or directories > # we don't want to check (depends on variables KASAN_SANITIZE_obj.o, KASAN_SANITIZE) > -- > 2.30.0.284.gd98b1dd5eaa7-goog > -- Thanks, ~Nick Desaulniers
