From: Andrew Morton <akpm@linux-foundation.org>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: Shaohua Li <shaohua.li@intel.com>, linux-mm <linux-mm@kvack.org>,
Andi Kleen <andi@firstfloor.org>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Rik van Riel <riel@redhat.com>, mel <mel@csn.ul.ie>,
Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH 2/2 v4]mm: batch activate_page() to reduce lock contention
Date: Mon, 14 Mar 2011 19:44:21 -0700 [thread overview]
Message-ID: <20110314194421.6474cfc5.akpm@linux-foundation.org> (raw)
In-Reply-To: <AANLkTimWH34vcJsykrtDq1Tb8W5qt+Os_FUtQO3+1qBX@mail.gmail.com>
On Tue, 15 Mar 2011 11:40:46 +0900 Minchan Kim <minchan.kim@gmail.com> wrote:
> On Tue, Mar 15, 2011 at 11:28 AM, Andrew Morton
> <akpm@linux-foundation.org> wrote:
> > On Tue, 15 Mar 2011 11:12:37 +0900 Minchan Kim <minchan.kim@gmail.com> wrote:
> >
> >> >> I can't understand why we should hanlde activate_page_pvecs specially.
> >> >> Please, enlighten me.
> >> > Not it's special. akpm asked me to do it this time. Reducing little
> >> > memory is still worthy anyway, so that's it. We can do it for other
> >> > pvecs too, in separate patch.
> >>
> >> Understandable but I don't like code separation by CONFIG_SMP for just
> >> little bit enhance of memory usage. In future, whenever we use percpu,
> >> do we have to implement each functions for both SMP and non-SMP?
> >> Is it desirable?
> >> Andrew, Is it really valuable?
> >
> > It's a little saving of text footprint. __It's also probably faster this way -
> > putting all the pages into a pagevec then later processing them won't
> > be very L1 cache friendly.
> >
> >
>
> I am not sure how much effective it is in UP. But if L1 cache friendly
> is important concern, we should not use per-cpu about hot operation.
It's not due to the percpu thing. The issue is putting 14 pages into a
pagevec and then later processing them after the older ones might have
fallen out of cache.
> I think more important thing in embedded (normal UP), it is a lock latency.
> I don't want to hold/release the lock per page.
There is no lock on UP builds.
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next prev parent reply other threads:[~2011-03-15 2:47 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-10 5:30 [PATCH 2/2 v4]mm: batch activate_page() to reduce lock contention Shaohua Li
2011-03-14 14:45 ` Minchan Kim
2011-03-15 1:53 ` Shaohua Li
2011-03-15 2:12 ` Minchan Kim
2011-03-15 2:28 ` Andrew Morton
2011-03-15 2:40 ` Minchan Kim
2011-03-15 2:44 ` Andrew Morton [this message]
2011-03-15 2:59 ` Minchan Kim
2011-03-15 2:32 ` KOSAKI Motohiro
2011-03-15 2:43 ` Minchan Kim
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