(Add pahole maintainer and mailing list) Hi Arnaldo, We're running into kernel build failure on 32-bit (both full 32-bit and 32-bit userspace on 64-bit kernel) because pahole crashed due to virtual memory exhaustion[1]. As a workaround we currently limit pahole's parallel job count to 1 on such system[2]: On Tue, 20 Aug 2024 10:59:50AM +0200, Jiri Slaby wrote: [...] > diff --git a/scripts/Makefile.btf b/scripts/Makefile.btf > index b75f09f3f424..f7de8e922bce 100644 > --- a/scripts/Makefile.btf > +++ b/scripts/Makefile.btf > @@ -12,7 +12,9 @@ endif > > pahole-flags-$(call test-ge, $(pahole-ver), 121) += --btf_gen_floats > > +ifeq ($(CONFIG_PAHOLE_CLASS),ELF64) > pahole-flags-$(call test-ge, $(pahole-ver), 122) += -j > +endif > > pahole-flags-$(call test-ge, $(pahole-ver), 125) += --skip_encoding_btf_inconsistent_proto --btf_gen_optimized > > diff --git a/scripts/pahole-class.sh b/scripts/pahole-class.sh > new file mode 100644 > index 000000000000..d15a92077f76 > --- /dev/null > +++ b/scripts/pahole-class.sh > @@ -0,0 +1,21 @@ > +#!/bin/sh > +# SPDX-License-Identifier: GPL-2.0 > +# > +# Usage: $ ./pahole-class.sh pahole > +# > +# Prints pahole's ELF class, such as ELF64 > + > +if [ ! -x "$(command -v "$@")" ]; then > + echo 0 > + exit 1 > +fi > + > +PAHOLE="$(which "$@")" > +CLASS="$(readelf -h "$PAHOLE" 2>/dev/null | sed -n 's/.*Class: *// p')" > + > +# Scripts like scripts/dummy-tools/pahole > +if [ -n "$CLASS" ]; then > + echo "$CLASS" > +else > + echo ELF64 > +fi > -- This helped lowered the memory usage enough so pahole no longer crash: On Wed, Aug 21, 2024 at 09:29:57AM GMT, Jiri Slaby wrote: > On 21. 08. 24, 8:40, Jiri Slaby wrote: > > From https://bugzilla.suse.com/show_bug.cgi?id=1229450#c20: > > Run on 64bit: > > pahole -j32 -> 4.102 GB > > pahole -j16 -> 3.895 GB > > pahole -j1 -> 3.706 GB > > > > On 32bit (the same vmlinux): > > pahole -j32 -> 2.870 GB (crash) > > pahole -j16 -> 2.810 GB > > pahole -j1 -> 2.444 GB Jiri (Slaby) in the meanwhile has also proposed structure packing to further reduce memory usage. (Note: I think the numbers below are from a 64-bit machine) > From https://bugzilla.suse.com/show_bug.cgi?id=1229450#c21: > (In reply to Jiri Slaby from comment #20) > > | | | ->24.01% (954,816,480B) 0x489B4AB: UnknownInlinedFun > (dwarf_loader.c:959) > > So given this struct class_member is the largest consumer, running pahole on > pahole. The below results in 4.102 GB -> 3.585 GB savings. > > --- a/dwarves.h > +++ b/dwarves.h > @@ -487,14 +487,14 @@ int cu__for_all_tags(struct cu *cu, > */ > struct tag { > struct list_head node; > + const char *attribute; > + void *priv; > type_id_t type; > uint16_t tag; > + uint16_t recursivity_level; > bool visited; > bool top_level; > bool has_btf_type_tag; > - uint16_t recursivity_level; > - const char *attribute; > - void *priv; > }; > > // To use with things like type->type_enum == > perf_event_type+perf_user_event_type > @@ -1086,17 +1086,17 @@ static inline int function__inlined(const struct > function *func) > struct class_member { > struct tag tag; > const char *name; > + uint64_t const_value; > uint32_t bit_offset; > uint32_t bit_size; > uint32_t byte_offset; > int hole; > size_t byte_size; > + uint32_t alignment; > int8_t bitfield_offset; > uint8_t bitfield_size; > uint8_t bit_hole; > uint8_t bitfield_end:1; > - uint64_t const_value; > - uint32_t alignment; > uint8_t visited:1; > uint8_t is_static:1; > uint8_t has_bit_offset:1; >-- What do you think? IIUC pahole's memory usage is largely tied to the number of entries in vmlinux/kmodule DWARF, and there probably isn't much we could do about that. Shung-Hsi 1: https://bugzilla.suse.com/show_bug.cgi?id=1229450 2: https://lore.kernel.org/all/20240820085950.200358-1-jirislaby@xxxxxxxxxx/
