From: Rik van Riel <riel@redhat.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Richard Davies <richard@arachsys.com>, KVM <kvm@vger.kernel.org>,
QEMU-devel <qemu-devel@nongnu.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>, Avi Kivity <avi@redhat.com>,
Shaohua Li <shli@kernel.org>
Subject: Re: [Qemu-devel] [PATCH 2/6] mm: compaction: Acquire the zone->lru_lock as late as possible
Date: Thu, 20 Sep 2012 14:54:16 -0400 [thread overview]
Message-ID: <505B6658.1080706@redhat.com> (raw)
In-Reply-To: <1348149875-29678-3-git-send-email-mgorman@suse.de>
On 09/20/2012 10:04 AM, Mel Gorman wrote:
> Compactions migrate scanner acquires the zone->lru_lock when scanning a range
> of pages looking for LRU pages to acquire. It does this even if there are
> no LRU pages in the range. If multiple processes are compacting then this
> can cause severe locking contention. To make matters worse commit b2eef8c0
> (mm: compaction: minimise the time IRQs are disabled while isolating pages
> for migration) releases the lru_lock every SWAP_CLUSTER_MAX pages that are
> scanned.
>
> This patch makes two changes to how the migrate scanner acquires the LRU
> lock. First, it only releases the LRU lock every SWAP_CLUSTER_MAX pages if
> the lock is contended. This reduces the number of times it unnecessarily
> disables and re-enables IRQs. The second is that it defers acquiring the
> LRU lock for as long as possible. If there are no LRU pages or the only
> LRU pages are transhuge then the LRU lock will not be acquired at all
> which reduces contention on zone->lru_lock.
>
> Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
next prev parent reply other threads:[~2012-09-20 18:54 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-20 14:04 [Qemu-devel] [PATCH 0/6] Reduce compaction scanning and lock contention Mel Gorman
2012-09-20 14:04 ` [Qemu-devel] [PATCH 1/6] mm: compaction: Abort compaction loop if lock is contended or run too long Mel Gorman
2012-09-20 18:53 ` Rik van Riel
2012-09-20 14:04 ` [Qemu-devel] [PATCH 2/6] mm: compaction: Acquire the zone->lru_lock as late as possible Mel Gorman
2012-09-20 18:54 ` Rik van Riel [this message]
2012-09-20 14:04 ` [Qemu-devel] [PATCH 3/6] mm: compaction: Acquire the zone->lock " Mel Gorman
2012-09-20 18:54 ` Rik van Riel
2012-09-20 14:04 ` [Qemu-devel] [PATCH 4/6] Revert "mm: have order > 0 compaction start off where it left" Mel Gorman
2012-09-20 18:54 ` Rik van Riel
2012-09-20 14:04 ` [Qemu-devel] [PATCH 5/6] mm: compaction: Cache if a pageblock was scanned and no pages were isolated Mel Gorman
2012-09-20 18:55 ` Rik van Riel
2012-09-20 14:04 ` [Qemu-devel] [PATCH 6/6] mm: compaction: Restart compaction from near where it left off Mel Gorman
2012-09-20 18:57 ` Rik van Riel
2012-09-21 9:13 ` [Qemu-devel] [PATCH 0/6] Reduce compaction scanning and lock contention Richard Davies
2012-09-21 9:15 ` Richard Davies
2012-09-21 9:17 ` Richard Davies
2012-09-21 9:55 ` Mel Gorman
2012-09-21 9:18 ` Richard Davies
2012-09-21 9:35 ` Mel Gorman
2012-09-21 9:49 ` Richard Davies
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