linux-kernel - Re: [PATCH v5 00/10] perf sched: Introduce stats tool

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Message-ID: <6a434657-5b5b-41ec-a79a-c648c2829602@intel.com>
Date: Thu, 22 Jan 2026 00:09:25 +0800
From: "Chen, Yu C" <yu.c.chen@...el.com>
To: Swapnil Sapkal <swapnil.sapkal@....com>
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Subject: Re: [PATCH v5 00/10] perf sched: Introduce stats tool

On 1/20/2026 1:58 AM, Swapnil Sapkal wrote:
> MOTIVATION
> ----------
> 
> Existing `perf sched` is quite exhaustive and provides lot of insights
> into scheduler behavior but it quickly becomes impractical to use for
> long running or scheduler intensive workload. For ex, `perf sched record`
> has ~7.77% overhead on hackbench (with 25 groups each running 700K loops
> on a 2-socket 128 Cores 256 Threads 3rd Generation EPYC Server), and it
> generates huge 56G perf.data for which perf takes ~137 mins to prepare
> and write it to disk [1].
> 
> Unlike `perf sched record`, which hooks onto set of scheduler tracepoints
> and generates samples on a tracepoint hit, `perf sched stats record` takes
> snapshot of the /proc/schedstat file before and after the workload, i.e.
> there is almost zero interference on workload run. Also, it takes very
> minimal time to parse /proc/schedstat, convert it into perf samples and
> save those samples into perf.data file. Result perf.data file is much
> smaller. So, overall `perf sched stats record` is much more light weight
> compare to `perf sched record`.
> 
> We, internally at AMD, have been using this (a variant of this, known as
> "sched-scoreboard"[2]) and found it to be very useful to analyse impact
> of any scheduler code changes[3][4]. Prateek used v2[5] of this patch
> series to report the analysis[6][7].
> 
> Please note that, this is not a replacement of perf sched record/report.
> The intended users of the new tool are scheduler developers, not regular
> users.
> 
> USAGE
> -----
> 
>    # perf sched stats record
>    # perf sched stats report
>    # perf sched stats diff
> 
> Note: Although `perf sched stats` tool supports workload profiling syntax
> (i.e. -- <workload> ), the recorded profile is still systemwide since the
> /proc/schedstat is a systemwide file.
> 

I found this is useful for load balance analysis on my
384 CPUs system with 6.19.0-rc1, please feel free to add

Tested-by: Chen Yu <yu.c.chen@...el.com>

thanks,
Chenyu