From: Aaron Lu <aaron.lu@intel.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Huang Ying <ying.huang@intel.com>,
Dave Hansen <dave.hansen@intel.com>,
Kemi Wang <kemi.wang@intel.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Andi Kleen <ak@linux.intel.com>, Michal Hocko <mhocko@suse.com>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v2 1/2] free_pcppages_bulk: do not hold lock when picking pages to free
Date: Fri, 23 Feb 2018 09:42:46 +0800 [thread overview]
Message-ID: <20180223014245.GB4338@intel.com> (raw)
In-Reply-To: <20180215124644.GA12360@bombadil.infradead.org>
On Thu, Feb 15, 2018 at 04:46:44AM -0800, Matthew Wilcox wrote:
> On Thu, Jan 25, 2018 at 03:21:44PM +0800, Aaron Lu wrote:
> > When freeing a batch of pages from Per-CPU-Pages(PCP) back to buddy,
> > the zone->lock is held and then pages are chosen from PCP's migratetype
> > list. While there is actually no need to do this 'choose part' under
> > lock since it's PCP pages, the only CPU that can touch them is us and
> > irq is also disabled.
>
> I have no objection to this patch. If you're looking for ideas for
> future improvement though, I wonder whether using a LIST_HEAD is the
> best way to store these pages temporarily. If you batch them into a
> pagevec and then free the entire pagevec, the CPU should be a little
> faster scanning a short array than walking a linked list.
Thanks for the suggestion.
> It would also puts a hard boundary on how long zone->lock is held, as
> you'd drop it and go back for another batch after 15 pages. That might
> be bad, of course.
Yes that's a concern.
As Mel reponded in another email, I think I'll just keep using list
here.
>
> Another minor change I'd like to see is free_pcpages_bulk updating
> pcp->count itself; all of the callers do it currently.
Sounds good, I'll prepare a separate patch for this, thanks!
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next prev parent reply other threads:[~2018-02-23 1:41 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-24 2:30 [PATCH 1/2] free_pcppages_bulk: do not hold lock when picking pages to free Aaron Lu
2018-01-24 2:30 ` [PATCH 2/2] free_pcppages_bulk: prefetch buddy while not holding lock Aaron Lu
2018-01-24 16:43 ` Mel Gorman
2018-01-24 16:57 ` Dave Hansen
2018-01-24 18:19 ` Mel Gorman
2018-01-24 19:23 ` Dave Hansen
2018-01-24 21:12 ` Mel Gorman
2018-01-25 7:25 ` [PATCH v2 " Aaron Lu
2018-01-24 16:40 ` [PATCH 1/2] free_pcppages_bulk: do not hold lock when picking pages to free Mel Gorman
2018-01-25 7:21 ` [PATCH v2 " Aaron Lu
2018-02-15 12:06 ` Mel Gorman
2018-02-23 1:37 ` Aaron Lu
2018-02-15 12:46 ` Matthew Wilcox
2018-02-15 14:55 ` Mel Gorman
2018-02-23 1:42 ` Aaron Lu [this message]
2018-02-05 5:30 ` RFC: eliminate zone->lock contention for will-it-scale/page_fault1 on big server Aaron Lu
2018-02-05 5:31 ` [RFC PATCH 1/2] __free_one_page: skip merge for order-0 page unless compaction is in progress Aaron Lu
2018-02-05 22:17 ` Dave Hansen
2018-02-05 5:32 ` [RFC PATCH 2/2] rmqueue_bulk: avoid touching page structures under zone->lock Aaron Lu
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