On Thu, Oct 07, 2021 at 12:51:25PM +0300, Andy Shevchenko wrote: > The kernel.h is a set of something which is not related to each other > and often used in non-crossed compilation units, especially when drivers > need only one or two macro definitions from it. > > Here is the split of container_of(). The goals are the following: > - untwist the dependency hell a bit > - drop kernel.h inclusion where it's only used for container_of() > - speed up C preprocessing. > > People, like Greg KH and Miguel Ojeda, were asking about the latter. > Read below the methodology and test setup with outcome numbers. > > The methodology > =============== > The question here is how to measure in the more or less clean way > the C preprocessing time when building a project like Linux kernel. > To answer it, let's look around and see what tools do we have that > may help. Aha, here is ccache tool that seems quite plausible to > be used. Its core idea is to preprocess C file, count hash (MD4) > and compare to ones that are in the cache. If found, return the > object file, avoiding compilation stage. > > Taking into account the property of the ccache, configure and use > it in the below steps: > > 1. Configure kernel with allyesconfig > > 2. Make it with `make` to be sure that the cache is filled with > the latest data. I.o.w. warm up the cache. > > 3. Run `make -s` (silent mode to reduce the influence of > the unrelated things, like console output) 10 times and > measure 'real' time spent. > > 4. Repeat 1-3 for each patch or patch set to get data sets before > and after. > > When we get the raw data, calculating median will show us the number. > Comparing them before and after we will see the difference. > > The setup > ========= > I have used the Intel x86_64 server platform (see partial output of > `lscpu` below): > > $ lscpu > Architecture: x86_64 > CPU op-mode(s): 32-bit, 64-bit > Address sizes: 46 bits physical, 48 bits virtual > Byte Order: Little Endian > CPU(s): 88 > On-line CPU(s) list: 0-87 > Vendor ID: GenuineIntel > Model name: Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz > CPU family: 6 > Model: 79 > Thread(s) per core: 2 > Core(s) per socket: 22 > Socket(s): 2 > Stepping: 1 > CPU max MHz: 3600.0000 > CPU min MHz: 1200.0000 > ... > Caches (sum of all): > L1d: 1.4 MiB (44 instances) > L1i: 1.4 MiB (44 instances) > L2: 11 MiB (44 instances) > L3: 110 MiB (2 instances) > NUMA: > NUMA node(s): 2 > NUMA node0 CPU(s): 0-21,44-65 > NUMA node1 CPU(s): 22-43,66-87 > Vulnerabilities: > Itlb multihit: KVM: Mitigation: Split huge pages > L1tf: Mitigation; PTE Inversion; VMX conditional cache flushes, SMT vulnerable > Mds: Mitigation; Clear CPU buffers; SMT vulnerable > Meltdown: Mitigation; PTI > Spec store bypass: Mitigation; Speculative Store Bypass disabled via prctl and seccomp > Spectre v1: Mitigation; usercopy/swapgs barriers and __user pointer sanitization > Spectre v2: Mitigation; Full generic retpoline, IBPB conditional, IBRS_FW, STIBP conditional, RSB filling > Tsx async abort: Mitigation; Clear CPU buffers; SMT vulnerable > > With the following GCC: > > $ gcc --version > gcc (Debian 10.3.0-11) 10.3.0 > > The commands I have run during the measurement were: > > rm -rf $O > make O=$O allyesconfig > time make O=$O -s -j64 # this step has been measured > > The raw data and median > ======================= > Before patch 2 (yes, I have measured the only patch 2 effect) in the series > (the data is sorted by time): > > real 2m8.794s > real 2m11.183s > real 2m11.235s > real 2m11.639s > real 2m11.960s > real 2m12.014s > real 2m12.609s > real 2m13.177s > real 2m13.462s > real 2m19.132s > > After patch 2 has been applied: > > real 2m8.536s > real 2m8.776s > real 2m9.071s > real 2m9.459s > real 2m9.531s > real 2m9.610s > real 2m10.356s > real 2m10.430s > real 2m11.117s > real 2m11.885s > > Median values are: > 131.987s before > 129.571s after > > We see the steady speedup as of 1.83%. You do know about kcbench: https://gitlab.com/knurd42/kcbench.git Try running that to make it such that we know how it was tested :) thanks, greg k-h > > Andy Shevchenko (4): > kernel.h: Drop unneeded <linux/kernel.h> inclusion from other headers > kernel.h: Split out container_of() and typeof_member() macros > lib/rhashtable: Replace kernel.h with the necessary inclusions > kunit: Replace kernel.h with the necessary inclusions > > include/kunit/test.h | 14 ++++++++++++-- > include/linux/container_of.h | 37 ++++++++++++++++++++++++++++++++++++ > include/linux/kernel.h | 31 +----------------------------- > include/linux/kobject.h | 1 + > include/linux/list.h | 6 ++++-- > include/linux/llist.h | 4 +++- > include/linux/plist.h | 5 ++++- > include/linux/rwsem.h | 1 - > include/linux/spinlock.h | 1 - > include/media/media-entity.h | 3 ++- > lib/radix-tree.c | 6 +++++- > lib/rhashtable.c | 7 ++++++- > 12 files changed, 75 insertions(+), 41 deletions(-) > create mode 100644 include/linux/container_of.h > > -- > 2.33.0 >
