> On Wed, Jan 13, 2021 at 8:07 PM Nick Desaulniers > <ndesaulniers@xxxxxxxxxx> wrote: > > > > On Wed, Jan 13, 2021 at 12:55 PM Nathan Chancellor > > <natechancellor@xxxxxxxxx> wrote: > > > > > > However, I see an issue with actually using the data: > > > > > > $ sudo -s > > > # mount -t debugfs none /sys/kernel/debug > > > # cp -a /sys/kernel/debug/pgo/profraw vmlinux.profraw > > > # chown nathan:nathan vmlinux.profraw > > > # exit > > > $ tc-build/build/llvm/stage1/bin/llvm-profdata merge --output=vmlinux.profdata vmlinux.profraw > > > warning: vmlinux.profraw: Invalid instrumentation profile data (bad magic) > > > error: No profiles could be merged. > > > > > > Am I holding it wrong? :) Note, this is virtualized, I do not have any > > > "real" x86 hardware that I can afford to test on right now. > > > > Same. > > > > I think the magic calculation in this patch may differ from upstream > > llvm: https://github.com/llvm/llvm-project/blob/49142991a685bd427d7e877c29c77371dfb7634c/llvm/include/llvm/ProfileData/SampleProf.h#L96-L101 > > Err...it looks like it was the padding calculation. With that fixed > up, we can query the profile data to get insights on the most heavily > called functions. Here's what my top 20 are (reset, then watch 10 > minutes worth of cat videos on youtube while running `find /` and > sleeping at my desk). Anything curious stand out to anyone? Hello world from my personal laptop whose kernel was rebuilt with profiling data! Wow, I can run `find /` and watch cat videos on youtube so fast! Users will love this! /s Checking the sections sizes of .text.hot. and .text.unlikely. looks good! > > $ llvm-profdata show -topn=20 /tmp/vmlinux.profraw > Instrumentation level: IR entry_first = 0 > Total functions: 48970 > Maximum function count: 62070879 > Maximum internal block count: 83221158 > Top 20 functions with the largest internal block counts: > drivers/tty/n_tty.c:n_tty_write, max count = 83221158 > rcu_read_unlock_strict, max count = 62070879 > _cond_resched, max count = 25486882 > rcu_all_qs, max count = 25451477 > drivers/cpuidle/poll_state.c:poll_idle, max count = 23618576 > _raw_spin_unlock_irqrestore, max count = 18874121 > drivers/cpuidle/governors/menu.c:menu_select, max count = 18721624 > _raw_spin_lock_irqsave, max count = 18509161 > memchr, max count = 15525452 > _raw_spin_lock, max count = 15484254 > __mod_memcg_state, max count = 14604619 > __mod_memcg_lruvec_state, max count = 14602783 > fs/ext4/hash.c:str2hashbuf_signed, max count = 14098424 > __mod_lruvec_state, max count = 12527154 > __mod_node_page_state, max count = 12525172 > native_sched_clock, max count = 8904692 > sched_clock_cpu, max count = 8895832 > sched_clock, max count = 8894627 > kernel/entry/common.c:exit_to_user_mode_prepare, max count = 8289031 > fpregs_assert_state_consistent, max count = 8287198 > > -- > Thanks, > ~Nick Desaulniers >
