From: Tejun Heo <tj@kernel.org>
To: Mateusz Guzik <mjguzik@gmail.com>
Cc: "Greg Thelen" <gthelen@google.com>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Michal Koutný" <mkoutny@suse.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Eric Dumazet" <edumzaet@google.com>,
"Yosry Ahmed" <yosryahmed@google.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
"Eric Dumazet" <edumazet@google.com>
Subject: Re: [PATCH] cgroup/rstat: avoid disabling irqs for O(num_cpu)
Date: Wed, 19 Mar 2025 07:26:57 -1000 [thread overview]
Message-ID: <Z9r-YQDAXIur81i0@slm.duckdns.org> (raw)
In-Reply-To: <u5kcjffhyrjsxagpdzas7q463ldgqtptaafozea3bv64odn2xt@agx42ih5m76l>
On Wed, Mar 19, 2025 at 11:47:32AM +0100, Mateusz Guzik wrote:
...
> Is not this going a little too far?
>
> the lock + irq trip is quite expensive in its own right and now is
> going to be paid for each cpu, as in the total time spent executing
> cgroup_rstat_flush_locked is going to go up.
Lock/unlock when the cacheline is already on the cpu is pretty cheap and on
modern x86 cpus at least irq on/off are also only a few cycles, so you
probably wouldn't be able to tell the difference.
Thanks.
--
tejun
next prev parent reply other threads:[~2025-03-19 17:27 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-19 7:13 Greg Thelen
2025-03-19 7:17 ` Greg Thelen
2025-03-19 10:20 ` Michal Koutný
2025-03-19 10:47 ` Mateusz Guzik
2025-03-19 17:18 ` Yosry Ahmed
2025-03-27 14:38 ` Mateusz Guzik
2025-03-27 17:17 ` Yosry Ahmed
2025-03-27 17:47 ` Mateusz Guzik
2025-04-01 15:00 ` Michal Koutný
2025-04-01 15:46 ` Mateusz Guzik
2025-04-01 16:59 ` Michal Koutný
2025-03-19 17:26 ` Tejun Heo [this message]
2025-03-26 23:57 ` Mateusz Guzik
2025-03-19 17:16 ` Yosry Ahmed
2025-03-19 18:06 ` Johannes Weiner
2025-03-19 18:35 ` Yosry Ahmed
2025-03-19 19:10 ` Tejun Heo
2025-03-19 19:16 ` Johannes Weiner
2025-03-19 19:46 ` Johannes Weiner
2025-03-19 17:26 ` Tejun Heo
2025-03-19 17:35 ` Johannes Weiner
2025-03-19 17:53 ` Shakeel Butt
2025-03-19 18:37 ` Eric Dumazet
2025-03-20 14:43 ` Greg Thelen
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