From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: John Johansen <john.johansen@canonical.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Swapnil Sapkal <Swapnil.Sapkal@amd.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org,
Aaron Lu <aaron.lu@intel.com>,
x86@kernel.org, Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [tip: sched/core] sched: Fix performance regression introduced by mm_cid
Date: Fri, 23 Jun 2023 10:17:56 +0200 [thread overview]
Message-ID: <20230623081756.vVHIjkC9@linutronix.de> (raw)
In-Reply-To: <ed287d2f-5b53-dffb-dec3-e5b28fa70a52@canonical.com>
On 2023-06-23 00:35:29 [-0700], John Johansen wrote:
> >
> iirc the difference with the earlier version, is in the put case. Where in
> the earlier version, if there was lock contention the buffer would always
> get pushed onto the percpu list. With some debug patches on top we
> saw some degenerate cases where this would result in percpu lists that
> had excessive buffers on them.
>
> So this version added a condition to force putting the buffer back
> in to the global pool if the percpu list already has 2 buffers
> cached on it.
So none of the versions perform memory allocation/ deallocation in a
preempt disabled section so it is fine from PREEMPT_RT point of view.
Sebastian
next prev parent reply other threads:[~2023-06-23 8:18 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-22 7:43 tip-bot2 for Mathieu Desnoyers
2023-06-20 8:14 ` Swapnil Sapkal
2023-06-20 9:11 ` Peter Zijlstra
2023-06-20 10:35 ` Swapnil Sapkal
2023-06-20 10:51 ` Mathieu Desnoyers
2023-06-21 16:36 ` Swapnil Sapkal
2023-06-21 18:51 ` Mathieu Desnoyers
2023-06-21 21:41 ` Mathieu Desnoyers
2023-06-21 23:59 ` John Johansen
2023-06-22 14:33 ` Mathieu Desnoyers
2023-06-22 16:09 ` John Johansen
2023-06-23 6:52 ` Sebastian Andrzej Siewior
2023-06-23 6:37 ` Sebastian Andrzej Siewior
2023-06-23 7:16 ` John Johansen
2023-06-23 8:15 ` Sebastian Andrzej Siewior
2023-06-23 7:35 ` John Johansen
2023-06-23 8:17 ` Sebastian Andrzej Siewior [this message]
2023-07-14 6:02 ` Swapnil Sapkal
2023-07-14 14:55 ` Mathieu Desnoyers
2023-07-18 6:01 ` Swapnil Sapkal
2023-06-23 13:12 ` Linux regression tracking #adding (Thorsten Leemhuis)
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