From: CGEL <cgel.zte@gmail.com>
To: David Hildenbrand <david@redhat.com>
Cc: akpm@linux-foundation.org, bsingharora@gmail.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Yang Yang <yang.yang29@zte.com.cn>,
Ran Xiaokai <ran.xiaokai@zte.com.cn>
Subject: Re: [PATCH] delayacct: track delays from COW
Date: Wed, 23 Mar 2022 09:05:58 +0000 [thread overview]
Message-ID: <623ae2f9.1c69fb81.28ae2.21f3@mx.google.com> (raw)
In-Reply-To: <9f9ddbf7-797a-58d8-2903-beacb2698329@redhat.com>
On Wed, Mar 23, 2022 at 09:49:46AM +0100, David Hildenbrand wrote:
> On 22.03.22 12:04, cgel.zte@gmail.com wrote:
> > From: Yang Yang <yang.yang29@zte.com.cn>
> >
> > Delay accounting does not track the delay of COW. When tasks trigger
> > much COW, it may spend a amount of time waiting for it. To get the
> > impact of tasks in COW, measure the delay when it happens. This
> > could help users to do tunnings, such as decide whether to use
> > ksm or not.
> >
> > Also update tools/accounting/getdelays.c:
> >
> > / # ./getdelays -dl -p 231
> > print delayacct stats ON
> > listen forever
> > PID 231
> >
> > CPU count real total virtual total delay total delay average
> > 6247 1859000000 2154070021 1674255063 0.268ms
> > IO count delay total delay average
> > 0 0 0ms
> > SWAP count delay total delay average
> > 0 0 0ms
> > RECLAIM count delay total delay average
> > 0 0 0ms
> > THRASHING count delay total delay average
> > 0 0 0ms
> > COMPACT count delay total delay average
> > 3 72758 0ms
> > COW count delay total delay average
> > 3635 271567604 0ms
>
> You should also update Documentation/accounting/delay-accounting.rst
> most probably.
I will update this documentation immediately if this patch is merged.
> Overall LGTM and this might be of value not only for KSM but for anybody
> using fork(). There will be collisions with [1], especially [2], which I
> want to get in -next early after we have v5.18-rc1 (after rebasing [1]
> on top of this).
>
> We'll have to decide if we want to also account hugetlb wp code
> (hugetlb_cow), and if we want to account "unsharing" here as well under
> cow (I tend to say that we want to for simplicity). For THP, we only
> split and don't copy, so there isn't anything to account.
>
Thanks for your reminding, we will work on that too.
> [1] https://lore.kernel.org/r/20220315104741.63071-1-david@redhat.com
> [2] https://lore.kernel.org/r/20220315104741.63071-14-david@redhat.com
>
> --
> Thanks,
>
> David / dhildenb
next prev parent reply other threads:[~2022-03-23 9:06 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-22 11:04 [PATCH] delayacct: track delays from COW cgel.zte
2022-03-23 8:49 ` David Hildenbrand
2022-03-23 9:05 ` CGEL [this message]
2022-04-06 7:37 ` CGEL
2022-04-08 7:31 ` David Hildenbrand
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