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From: Vlastimil Babka <vbabka@suse.cz>
To: Mel Gorman <mgorman@techsingularity.net>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, Hugh Dickins <hughd@google.com>,
	Linux-MM <linux-mm@kvack.org>,
	Linux-RT-Users <linux-rt-users@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1] mm/vmstat: Protect per cpu variables with preempt disable on RT
Date: Fri, 6 Aug 2021 14:38:54 +0200	[thread overview]
Message-ID: <d54e0958-5680-0d5c-e4a7-6ec4afe53b48@suse.cz> (raw)
In-Reply-To: <20210805160019.1137-2-mgorman@techsingularity.net>

On 8/5/21 6:00 PM, Mel Gorman wrote:
> From: Ingo Molnar <mingo@elte.hu>
> 
> Disable preemption on -RT for the vmstat code. On vanila the code runs
> in IRQ-off regions while on -RT it may not when stats are updated under
> a local_lock. "preempt_disable" ensures that the same resources is not
> updated in parallel due to preemption.
> 
> This patch differs from the preempt-rt version where __count_vm_event and
> __count_vm_events are also protected. The counters are explicitly "allowed
> to be to be racy" so there is no need to protect them from preemption. Only
> the accurate page stats that are updated by a read-modify-write need
> protection. This patch also differs in that a preempt_[en|dis]able_rt
> helper is not used. As vmstat is the only user of the helper, it was
> suggested that it be open-coded in vmstat.c instead of risking the helper
> being used in unnecessary contexts.
> 
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

  parent reply	other threads:[~2021-08-06 12:39 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-05 16:00 [PATCH 0/1 v2] Protect vmstats on PREEMPT_RT Mel Gorman
2021-08-05 16:00 ` [PATCH 1/1] mm/vmstat: Protect per cpu variables with preempt disable on RT Mel Gorman
2021-08-05 23:22   ` Andrew Morton
2021-08-06  7:50     ` Vlastimil Babka
2021-08-06  8:44     ` Mel Gorman
2021-08-06 12:38   ` Vlastimil Babka [this message]
2021-08-31 16:45   ` Sebastian Andrzej Siewior
2021-09-02 20:07     ` Andrew Morton
2021-09-06 13:48     ` Mel Gorman
2021-09-06 14:03       ` Sebastian Andrzej Siewior

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