From: Mel Gorman <mgorman@techsingularity.net>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-mm@kvack.org, tglx@linutronix.de, frederic@kernel.org
Subject: Re: [PATCH 0/2] mm/swap: Add locking for pagevec
Date: Mon, 15 Oct 2018 10:50:48 +0100 [thread overview]
Message-ID: <20181015095048.GG5819@techsingularity.net> (raw)
In-Reply-To: <02dd6505-2ee5-c1c1-2603-b759bc90d479@suse.cz>
On Fri, Oct 12, 2018 at 09:21:41AM +0200, Vlastimil Babka wrote:
> On 9/14/18 4:59 PM, Sebastian Andrzej Siewior wrote:
> I think this evaluation is missing the other side of the story, and
> that's the cost of using a spinlock (even uncontended) instead of
> disabling preemption. The expectation for LRU pagevec is that the local
> operations will be much more common than draining of other CPU's, so
> it's optimized for the former.
>
Agreed, the drain operation should be extremely rare except under heavy
memory pressure, particularly if mixed with THP allocations. The overall
intent seems to be improving lockdep coverage but I don't think we
should take a hit in the common case just to get that coverage. Bear in
mind that the main point of the pagevec (whether it's true or not) is to
avoid the much heavier LRU lock.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2018-10-15 9:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-14 14:59 [PATCH 0/2] mm/swap: Add locking for pagevec Sebastian Andrzej Siewior
2018-09-14 14:59 ` [PATCH 1/2] mm/swap: Add pagevec locking Sebastian Andrzej Siewior
2018-09-30 3:16 ` [LKP] [mm/swap] d884021f52: will-it-scale.per_process_ops -2.4% regression kernel test robot
2018-09-30 8:17 ` Sebastian Andrzej Siewior
2018-09-14 14:59 ` [PATCH 2/2] mm/swap: Access struct pagevec remotely Sebastian Andrzej Siewior
2018-11-09 23:06 ` Andrew Morton
2018-10-12 7:21 ` [PATCH 0/2] mm/swap: Add locking for pagevec Vlastimil Babka
2018-10-15 9:50 ` Mel Gorman [this message]
2018-10-16 16:26 ` Frederic Weisbecker
2018-10-16 17:13 ` Thomas Gleixner
2018-10-16 19:54 ` Frederic Weisbecker
2018-10-16 20:44 ` Thomas Gleixner
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