Re: [uprobes/x86] 8ad8e9d3fd6: -7.5% aim7.2000.jobs-per-min, -45.7% turbostat.%c1

From: Oleg Nesterov
Date: Thu May 15 2014 - 08:34:04 EST


Hi Jet,

On 05/15, Jet Chen wrote:
>
> we noticed the below changes on
>
> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> commit 8ad8e9d3fd64f101eed6652964670672d699e563 ("uprobes/x86: Introduce uprobe_xol_ops and arch_uprobe->ops")
>
> Test case: lkp-snb01/aim7/signal_test
>
> 34e7317d6ae8f61 8ad8e9d3fd64f101eed665296
> --------------- -------------------------
> 230689 ~ 0% -7.5% 213485 ~ 0% TOTAL aim7.2000.jobs-per-min
> 0.51 ~30% -45.7% 0.28 ~10% TOTAL turbostat.%c1
> 430 ~17% +27.8% 549 ~15% TOTAL vmstat.procs.r
> 0.83 ~14% +38.1% 1.15 ~12% TOTAL perf-profile.cpu-cycles.copy_pte_range.copy_page_range.copy_process.do_fork.sys_clone
> 106076 ~ 4% +22.4% 129816 ~ 3% TOTAL softirqs.RCU
> 12117 ~ 6% -9.9% 10914 ~ 6% TOTAL slabinfo.kmalloc-256.active_objs
> 32163 ~17% +39.4% 44824 ~12% TOTAL time.voluntary_context_switches
> 276487 ~ 1% +16.5% 322091 ~ 1% TOTAL time.involuntary_context_switches
> 83.14 ~ 0% +13.3% 94.21 ~ 0% TOTAL time.user_time
> 108800 ~ 2% +9.4% 119014 ~ 3% TOTAL time.minor_page_faults
> 1255 ~ 0% +9.9% 1379 ~ 0% TOTAL time.system_time
> 6774 ~ 1% +8.8% 7373 ~ 1% TOTAL vmstat.system.cs
> 52.15 ~ 0% +8.0% 56.34 ~ 0% TOTAL time.elapsed_time
> 25185 ~ 0% +2.4% 25784 ~ 0% TOTAL vmstat.system.in
> 79.23 ~ 0% +2.0% 80.80 ~ 0% TOTAL turbostat.%c0
> 2567 ~ 0% +1.9% 2615 ~ 0% TOTAL time.percent_of_cpu_this_job_got
> 112 ~ 0% +1.3% 113 ~ 0% TOTAL turbostat.Cor_W
> 138 ~ 0% +1.0% 139 ~ 0% TOTAL turbostat.Pkg_W

Cough... this looks simply impossible ;)

Not only this patch "obviously can not" cause any noticable difference
performance-wise, the code changed by this patch is not executed unless
you play with uprobes?

Oleg.

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