linux-kernel - Re: [PATCH] ring-buffer: speed up buffer resets by avoiding synchronize

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Message-Id: <1593482725.5cl7vnne3j.astroid@bobo.none>
Date:   Tue, 30 Jun 2020 12:07:05 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Anton Blanchard <anton@...abs.org>, linux-kernel@...r.kernel.org,
        Paul McKenney <paulmck@...nel.org>
Subject: Re: [PATCH] ring-buffer: speed up buffer resets by avoiding
 synchronize_rcu for each CPU

Excerpts from Steven Rostedt's message of June 30, 2020 8:16 am:
> On Thu, 25 Jun 2020 15:34:03 +1000
> Nicholas Piggin <npiggin@...il.com> wrote:
> 
>> Batch these up so we disable all the per-cpu buffers first, then
>> synchronize_rcu() once, then reset each of the buffers. This brings
>> the time down to about 0.5s.
> 
> After applying this patch, running tools/testing/selftests/ftracetest
> went from 5 minutes and 35 seconds to 5 minutes 5 seconds to complete
> on my 4 core (8 with hyperthreading) machine! That's almost a 10% drop!
> 
> Thanks, I'm definitely applying this for the next merge window.

Cool, always good when a big system optimisation helps small ones as 
well. Thanks all.

Thanks,
Nick