netdev - Re: [PATCH v1] cgroup/rstat: add cgroup_rstat_cpu

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Message-ID: <mw4bi6x5tx7rjgswp3ibd5wvnveqjlh3k3v6l3hor52pyejff2@x6ypubxztw4d>
Date: Fri, 3 May 2024 11:11:20 -0700
From: Shakeel Butt <shakeel.butt@...ux.dev>
To: Jesper Dangaard Brouer <hawk@...nel.org>
Cc: Waiman Long <longman@...hat.com>, tj@...nel.org, hannes@...xchg.org, 
	lizefan.x@...edance.com, cgroups@...r.kernel.org, yosryahmed@...gle.com, 
	netdev@...r.kernel.org, linux-mm@...ck.org, kernel-team@...udflare.com, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH v1] cgroup/rstat: add cgroup_rstat_cpu_lock helpers and
 tracepoints

On Fri, May 03, 2024 at 02:58:56PM +0200, Jesper Dangaard Brouer wrote:
> 
> 
> On 02/05/2024 21.44, Shakeel Butt wrote:
> > On Wed, May 01, 2024 at 07:22:26PM +0200, Jesper Dangaard Brouer wrote:
> > > 
> > [...]
> > > 
> > > More data, the histogram of time spend under the lock have some strange
> > > variation issues with a group in 4ms to 65ms area. Investigating what
> > > can be causeing this... which next step depend in these tracepoints.
> > > 
> > > @lock_cnt: 759146
> > > 
> > > @locked_ns:
> > > [1K, 2K)             499 |      |
> > > [2K, 4K)          206928
> > > |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@|
> > > [4K, 8K)          147904 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@      |
> > > [8K, 16K)          64453 |@@@@@@@@@@@@@@@@      |
> > > [16K, 32K)        135467 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@      |
> > > [32K, 64K)         75943 |@@@@@@@@@@@@@@@@@@@      |
> > > [64K, 128K)        38359 |@@@@@@@@@      |
> > > [128K, 256K)       46597 |@@@@@@@@@@@      |
> > > [256K, 512K)       32466 |@@@@@@@@      |
> > > [512K, 1M)          3945 |      |
> > > [1M, 2M)             642 |      |
> > > [2M, 4M)             750 |      |
> > > [4M, 8M)            1932 |      |
> > > [8M, 16M)           2114 |      |
> > > [16M, 32M)          1039 |      |
> > > [32M, 64M)           108 |      |
> > > 
> > 
> > Am I understanding correctly that 1K is 1 microsecond and 1M is 1
> > millisecond?
> 
> Correct.
> 
> > Is it possible to further divide this table into update
> > side and flush side?
> > 
> 
> This is *only* flush side.
> 
> You question indicate, that we are talking past each-other ;-)
> 
> Measurements above is with (recently) accepted tracepoints (e.g. not the
> proposed tracepoints in this patch).  I'm arguing with existing
> tracepoint that I'm seeing this data, and arguing I need per-CPU
> tracepoints to dig deeper into this (as proposed in this patch).

Ah my mistake, I just assumed that the data shown is with the given
patchset.

> 
> The "update side" can only be measured once we apply this patch.
> 
> This morning I got 6 prod machines booted with new kernels, that contain
> this proposed per-CPU lock tracepoint patch.  And 3 of these machines have
> the Mutex lock change also.  No data to share yet...
> 

Eagerly waiting for the results. Also I don't have any concerns with
these new traces.

> --Jesper