Re: [PATCH 0/5] perf sched: Introduce stats tool

[Madadi Vineeth Reddy <vineethr@linux.ibm.com>]

Hi Ravi,

On 16/09/24 22:17, Ravi Bangoria 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

per.data file is empty after the record.

Error:
The perf.data data has no samples!

Thanks and Regards
Madadi Vineeth Reddy

> 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].
> 
> 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.