From: Lucas Stach <l.stach@pengutronix.de>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, kernel@pengutronix.de,
patchwork-lst@pengutronix.de
Subject: Re: [PATCH] mm: page_alloc: avoid excessive IRQ disabled times in free_unref_page_list
Date: Fri, 08 Dec 2017 11:03:23 +0100 [thread overview]
Message-ID: <1512727403.11506.21.camel@pengutronix.de> (raw)
In-Reply-To: <20171207195103.dkiqjoeasr35atqj@techsingularity.net>
Am Donnerstag, den 07.12.2017, 19:51 +0000 schrieb Mel Gorman:
> On Thu, Dec 07, 2017 at 06:03:14PM +0100, Lucas Stach wrote:
> > Since 9cca35d42eb6 (mm, page_alloc: enable/disable IRQs once when
> > freeing
> > a list of pages) we see excessive IRQ disabled times of up to 250ms
> > on an
> > embedded ARM system (tracing overhead included).
> >
> > This is due to graphics buffers being freed back to the system via
> > release_pages(). Graphics buffers can be huge, so it's not hard to
> > hit
> > cases where the list of pages to free has 2048 entries. Disabling
> > IRQs
> > while freeing all those pages is clearly not a good idea.
> >
>
> 250ms to free 2048 entries? That seems excessive but I guess the
> embedded ARM system is not that fast.
Urgh, yes, I've messed up the order of magnitude in the commit log. It
really is on the order of 25ms. Which is still prohibitively long for
an IRQs off section.
Regards,
Lucas
> > Introduce a batch limit, which allows IRQ servicing once every few
> > pages.
> > The batch count is the same as used in other parts of the MM
> > subsystem
> > when dealing with IRQ disabled regions.
> >
> > Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
>
> Thanks.
>
> Acked-by: Mel Gorman <mgorman@techsingularity.net>
>
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next prev parent reply other threads:[~2017-12-08 10:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-07 17:03 [PATCH] mm: page_alloc: avoid excessive IRQ disabled times in free_unref_page_list Lucas Stach
2017-12-07 19:51 ` Mel Gorman
2017-12-07 23:20 ` Andrew Morton
2017-12-08 0:25 ` Mel Gorman
2017-12-08 0:53 ` Andrew Morton
2017-12-08 10:21 ` Mel Gorman
2017-12-08 10:03 ` Lucas Stach [this message]
2017-12-08 11:38 ` Mel Gorman
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