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From: "Michal Koutný" <mkoutny@suse.com>
To: 史思远 <shisiyuan19870131@gmail.com>
Cc: Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] cgroup: Return if dst_cgrp equals to src_cgrp
Date: Thu, 26 May 2022 13:22:28 +0200	[thread overview]
Message-ID: <20220526112228.GG11007@blackbody.suse.cz> (raw)
In-Reply-To: <CAC=y0ud7oPtFqj=dqBSicoWwoN0knAwA6svidiYjbFn9BJMR3w@mail.gmail.com>

On Thu, May 26, 2022 at 12:40:17PM +0800, 史思远 <shisiyuan19870131@gmail.com> wrote:
> echo 1413 >  /dev/cpuset/foreground/cgroup.procs
> echo 1413 >  /dev/cpuset/foreground/cgroup.procs
> echo 1413 >  /dev/cpuset/foreground/cgroup.procs

Thank you.

> In this situation, since the second echo, dst_cgrp equals to src_cgrp(both
> cgroups are the 'foreground' cpuset).
> cgroup1_procs_write（）-> __cgroup1_procs_write()
> -> cgrp = cgroup_kn_lock_live()
> -> task = cgroup_procs_write_start(buf...)
> -> cgroup_attach_task(cgrp, task, threadgroup);
>   -> 1) cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx);  //
> detect the (src_cgrp == dst_cgrp), don't need to continue the following
> migration flow.
>   -> 2) cgroup_migrate_prepare_dst(&mgctx)

Here, I'd like to let you know about [1]

>   -> 3) cgroup_migrate(leader, threadgroup, &mgctx)
>   -> 4) cgroup_migrate_finish(&mgctx) // cleanup
> -> cgroup_procs_write_finish();  // cleanup


> >> The main purpose for this patch is to handle the situation above, and
> just noticed that cgroup_update_dfl_csses() also
> calls cgroup_migrate_add_src(). So I assume it's a similar situation. We
> can discuss more about it.

So I think the patch doesn't save that much and identical css_set is
better condition to check on (covers cgroup_update_dfl_csses too).

Michal

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/cgroup/cgroup.c?h=v5.18#n2710

WARNING: multiple messages have this Message-ID (diff)
From: "Michal Koutný" <mkoutny-IBi9RG/b67k@public.gmane.org>
To: 史思远 <shisiyuan19870131-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>,
	Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] cgroup: Return if dst_cgrp equals to src_cgrp
Date: Thu, 26 May 2022 13:22:28 +0200	[thread overview]
Message-ID: <20220526112228.GG11007@blackbody.suse.cz> (raw)
In-Reply-To: <CAC=y0ud7oPtFqj=dqBSicoWwoN0knAwA6svidiYjbFn9BJMR3w-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Thu, May 26, 2022 at 12:40:17PM +0800, 史思远 <shisiyuan19870131-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> echo 1413 >  /dev/cpuset/foreground/cgroup.procs
> echo 1413 >  /dev/cpuset/foreground/cgroup.procs
> echo 1413 >  /dev/cpuset/foreground/cgroup.procs

Thank you.

> In this situation, since the second echo, dst_cgrp equals to src_cgrp(both
> cgroups are the 'foreground' cpuset).
> cgroup1_procs_write（）-> __cgroup1_procs_write()
> -> cgrp = cgroup_kn_lock_live()
> -> task = cgroup_procs_write_start(buf...)
> -> cgroup_attach_task(cgrp, task, threadgroup);
>   -> 1) cgroup_migrate_add_src(task_css_set(task), dst_cgrp, &mgctx);  //
> detect the (src_cgrp == dst_cgrp), don't need to continue the following
> migration flow.
>   -> 2) cgroup_migrate_prepare_dst(&mgctx)

Here, I'd like to let you know about [1]

>   -> 3) cgroup_migrate(leader, threadgroup, &mgctx)
>   -> 4) cgroup_migrate_finish(&mgctx) // cleanup
> -> cgroup_procs_write_finish();  // cleanup


> >> The main purpose for this patch is to handle the situation above, and
> just noticed that cgroup_update_dfl_csses() also
> calls cgroup_migrate_add_src(). So I assume it's a similar situation. We
> can discuss more about it.

So I think the patch doesn't save that much and identical css_set is
better condition to check on (covers cgroup_update_dfl_csses too).

Michal

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/cgroup/cgroup.c?h=v5.18#n2710

  parent reply	other threads:[~2022-05-26 11:23 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-20 17:02 [PATCH] cgroup: Return if dst_cgrp equals to src_cgrp shisiyuan
2022-05-20 17:02 ` shisiyuan
2022-05-25 22:51 ` Michal Koutný
     [not found]   ` <CAC=y0ud7oPtFqj=dqBSicoWwoN0knAwA6svidiYjbFn9BJMR3w@mail.gmail.com>
2022-05-26 11:22     ` Michal Koutný [this message]
2022-05-26 11:22       ` Michal Koutný

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