From: Tejun Heo <tj@kernel.org>
To: Chris Down <chris@chrisdown.name>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Michal Koutný" <mkoutny@suse.com>,
"Serge Hallyn" <serge.hallyn@ubuntu.com>,
driver-core@lists.linux.dev, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@meta.com
Subject: Re: [PATCH] kernfs: Build paths in linear time with respect to depth
Date: Sun, 15 Nov 2026 05:17:42 -1000 [thread overview]
Message-ID: <e4f172e286a51e9969b8a5cbf1a7da72@kernel.org> (raw)
In-Reply-To: <20261114142137.ecf5e6af6608b218@chrisdown.name>
Hello, Chris.
On Sat, Nov 14, 2026 at 02:21:37PM -0800, Chris Down wrote:
> What bothers me more is that whoever picks the depth isn't the one who is
> affected by it. cgroup.max.depth defaults to max, so anyone with a
> delegated subtree can make a deep chain. Every read of /proc/<pid>/cgroup
> for a task at the bottom of it then takes that long with css_set_lock held
> and IRQs off. It doesn't take five digits for that to become problematic,
> either.
...
I'd say three digits is already pretty extreme, and I think it's on the
parent to set cgroup.max.depth when delegating a subtree. It's similar to
e.g. memory.high. If the parent doesn't set it, a child can affect others
that are unrelated to it.
That said, I don't see any reason not to improve it.
Thanks.
--
tejun
prev parent reply other threads:[~2026-11-15 15:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-08 3:16 [PATCH] kernfs: Build paths in linear time with respect to depth Chris Down
2026-11-08 3:19 ` Chris Down
2026-11-09 15:43 ` Tejun Heo
2026-11-14 22:21 ` Chris Down
2026-11-15 15:17 ` Tejun Heo [this message]
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