From: Tejun Heo <tj@kernel.org>
To: Hugh Dickins <hughd@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>,
Shakeel Butt <shakeelb@google.com>,
Josef Bacik <josef@toxicpanda.com>, Jens Axboe <axboe@kernel.dk>,
Zefan Li <lizefan.x@bytedance.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
Vasily Averin <vasily.averin@linux.dev>,
cgroups@vger.kernel.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
bpf@vger.kernel.org
Subject: Re: [RFC PATCH 1/7] cgroup: rstat: only disable interrupts for the percpu lock
Date: Thu, 30 Mar 2023 15:51:35 -1000 [thread overview]
Message-ID: <ZCY8p/i6DR2tXPLP@slm.duckdns.org> (raw)
In-Reply-To: <98cb3ce-7ed9-3d17-9015-ef7193d6627@google.com>
Hello, Hugh.
On Wed, Mar 29, 2023 at 01:38:48PM -0700, Hugh Dickins wrote:
> > So, in general, there's a trade off between local irq service latency and
> > inducing global lock contention when using unprotected locks. With more and
> > more CPUs, the balance keeps shifting. The balance still very much depends
> > on the specifics of a given lock but yeah I think it's something we need to
> > be a lot more careful about now.
>
> And this looks a very plausible argument to me: I'll let it sink in.
Another somewhat relevant change is that flipping irq on/off used to be
relatively expensive on older x86 cpus. I forget all details about when and
how much but they should be a lot cheaper now. No idea about !x86 cpus tho.
> But I hadn't heard that the RT folks were clamouring for more irq disabling:
> perhaps they partition their machines with more care, and are not devotees
> of high CPU counts.
I think RT folks care a lot more about raw IRQ disables. These shouldn't
actually disable IRQs on RT kernels.
Thanks.
--
tejun
next prev parent reply other threads:[~2023-03-31 1:51 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-23 4:00 [RFC PATCH 0/7] Make rstat flushing IRQ and sleep friendly Yosry Ahmed
2023-03-23 4:00 ` [RFC PATCH 1/7] cgroup: rstat: only disable interrupts for the percpu lock Yosry Ahmed
2023-03-23 4:29 ` Shakeel Butt
2023-03-23 5:15 ` Yosry Ahmed
2023-03-23 6:33 ` Shakeel Butt
2023-03-23 13:35 ` Yosry Ahmed
2023-03-23 15:40 ` Shakeel Butt
2023-03-23 15:42 ` Yosry Ahmed
2023-03-23 15:46 ` Shakeel Butt
2023-03-23 16:09 ` Shakeel Butt
2023-03-23 16:17 ` Yosry Ahmed
2023-03-23 16:29 ` Shakeel Butt
2023-03-23 16:36 ` Yosry Ahmed
2023-03-23 16:45 ` Shakeel Butt
2023-03-23 16:51 ` Yosry Ahmed
2023-03-23 19:09 ` Shakeel Butt
2023-03-23 17:33 ` Johannes Weiner
2023-03-23 18:09 ` Yosry Ahmed
2023-03-23 18:19 ` Johannes Weiner
2023-03-24 1:39 ` Tejun Heo
2023-03-24 7:22 ` Yosry Ahmed
2023-03-24 14:12 ` Waiman Long
2023-03-24 22:50 ` Yosry Ahmed
2023-03-25 1:54 ` Tejun Heo
2023-03-25 2:17 ` Yosry Ahmed
2023-03-25 4:30 ` Shakeel Butt
2023-03-25 4:37 ` Yosry Ahmed
2023-03-25 4:46 ` Shakeel Butt
2023-03-27 23:23 ` Yosry Ahmed
2023-03-29 18:53 ` Tejun Heo
2023-03-29 19:22 ` Hugh Dickins
2023-03-29 20:00 ` Tejun Heo
2023-03-29 20:38 ` Hugh Dickins
2023-03-30 4:26 ` Yosry Ahmed
2023-03-31 1:51 ` Tejun Heo [this message]
2023-03-23 4:00 ` [RFC PATCH 2/7] memcg: do not disable interrupts when holding stats_flush_lock Yosry Ahmed
2023-03-23 4:32 ` Shakeel Butt
2023-03-23 5:16 ` Yosry Ahmed
2023-03-23 4:00 ` [RFC PATCH 3/7] cgroup: rstat: remove cgroup_rstat_flush_irqsafe() Yosry Ahmed
2023-03-23 15:43 ` Johannes Weiner
2023-03-23 15:45 ` Yosry Ahmed
2023-03-23 4:00 ` [RFC PATCH 4/7] memcg: sleep during flushing stats in safe contexts Yosry Ahmed
2023-03-23 15:56 ` Johannes Weiner
2023-03-23 16:01 ` Yosry Ahmed
2023-03-23 17:27 ` Johannes Weiner
2023-03-23 18:07 ` Yosry Ahmed
2023-03-23 19:35 ` Shakeel Butt
2023-03-23 4:00 ` [RFC PATCH 5/7] vmscan: memcg: sleep when flushing stats during reclaim Yosry Ahmed
2023-03-23 4:00 ` [RFC PATCH 6/7] workingset: memcg: sleep when flushing stats in workingset_refault() Yosry Ahmed
2023-03-23 15:50 ` Johannes Weiner
2023-03-23 16:02 ` Yosry Ahmed
2023-03-23 16:00 ` Johannes Weiner
2023-03-23 16:02 ` Yosry Ahmed
2023-03-23 4:00 ` [RFC PATCH 7/7] memcg: do not modify rstat tree for zero updates Yosry Ahmed
2023-03-23 4:10 ` [RFC PATCH 0/7] Make rstat flushing IRQ and sleep friendly Shakeel Butt
2023-03-23 5:07 ` Yosry Ahmed
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