From: Andrew Morton <akpm@linux-foundation.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>,
zhang.mingjun@linaro.org, m.szyprowski@samsung.com,
haojian.zhuang@linaro.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
Mingjun Zhang <troy.zhangmingjun@linaro.org>
Subject: Re: [PATCH] mm: cma: free cma page to buddy instead of being cpu hot page
Date: Wed, 6 Nov 2013 15:41:20 -0800 [thread overview]
Message-ID: <20131106154120.477a4cd83f8fb120d4d4f6cf@linux-foundation.org> (raw)
In-Reply-To: <20131106064302.GC30958@bbox>
On Wed, 6 Nov 2013 15:43:02 +0900 Minchan Kim <minchan@kernel.org> wrote:
> > The added overhead is pretty small - just a comparison of a local with
> > a constant. And that cost is not incurred for MIGRATE_UNMOVABLE,
> > MIGRATE_RECLAIMABLE and MIGRATE_MOVABLE, which are the common cases
> > (yes?).
>
> True but bloat code might affect icache so we should be careful.
> And what Mel has a concern is about zone->lock, which would be more contended.
> I agree his opinion.
>
> In addition, I think the gain is marginal because normally CMA is big range
> so free_contig_range in dma release path will fill per_cpu_pages with freed pages
> easily so it could drain per_cpu_pages frequently so race which steal page from
> per_cpu_pages is not big, I guess.
>
> Morever, we could change free_contig_range with batch_free_page which would
> be useful for other cases if they want to free many number of pages
> all at once.
>
> The bottom line is we need *number and real scenario* for that.
Well yes, quantitative results are always good to have with a patch like
this.
It doesn't actually compile (missing a "}"), which doesn't inspire
confidence. I'll make the patch go away for now
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prev parent reply other threads:[~2013-11-06 23:41 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-28 11:42 zhang.mingjun
2013-10-28 16:04 ` Laura Abbott
2013-10-29 4:54 ` Minchan Kim
2013-10-29 6:41 ` KOSAKI Motohiro
2013-10-29 7:00 ` Zhang Mingjun
2013-10-29 7:25 ` Minchan Kim
2013-10-29 11:17 ` Zhang Mingjun
2013-10-29 9:33 ` Mel Gorman
2013-10-29 11:49 ` Zhang Mingjun
2013-10-29 12:27 ` Mel Gorman
2013-10-29 15:02 ` Zhang Mingjun
2013-10-29 16:14 ` Laura Abbott
2013-10-30 5:40 ` Minchan Kim
2013-10-31 2:14 ` Laura Abbott
2013-11-01 1:49 ` Minchan Kim
2013-12-23 12:38 ` Wanpeng Li
2013-10-30 2:55 ` Minchan Kim
2013-11-05 21:44 ` Andrew Morton
2013-11-06 6:43 ` Minchan Kim
2013-11-06 23:41 ` Andrew Morton [this message]
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