From: Rik van Riel <riel@redhat.com>
To: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: linux-mm@kvack.org, aarcange@redhat.com,
linux-kernel@vger.kernel.org, Mel Gorman <mel@csn.ul.ie>,
akpm@linux-foundation.org, Johannes Weiner <hannes@cmpxchg.org>,
hughd@google.com
Subject: Re: [PATCH -mm 2/2] mm: kswapd carefully invoke compaction
Date: Wed, 11 Jan 2012 08:34:06 -0500 [thread overview]
Message-ID: <4F0D8FCE.7080202@redhat.com> (raw)
In-Reply-To: <CAHGf_=rj=aDVGWXqdq7fh_LrCFnug_mPNuuE=YdXaWpvwyjfzg@mail.gmail.com>
On 01/11/2012 02:25 AM, KOSAKI Motohiro wrote:
>> With CONFIG_COMPACTION enabled, kswapd does not try to free
>> contiguous free pages, even when it is woken for a higher order
>> request.
>>
>> This could be bad for eg. jumbo frame network allocations, which
>> are done from interrupt context and cannot compact memory themselves.
>> Higher than before allocation failure rates in the network receive
>> path have been observed in kernels with compaction enabled.
>>
>> Teach kswapd to defragment the memory zones in a node, but only
>> if required and compaction is not deferred in a zone.
>>
>> Signed-off-by: Rik van Riel<riel@redhat.com>
>
> I agree with we need asynchronous defragmentations feature. But, do we
> really need to use kswapd for compaction? While kswapd take a
> compaction work, it can't work to make free memory.
I believe we do need some background compaction, especially
to help allocations from network interrupts.
If you believe the compaction is better done from some
other thread, I guess we could do that, but truthfully, if
kswapd spends a lot of time doing compaction, I made a
mistake somewhere :)
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WARNING: multiple messages have this Message-ID (diff)
From: Rik van Riel <riel@redhat.com>
To: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: linux-mm@kvack.org, aarcange@redhat.com,
linux-kernel@vger.kernel.org, Mel Gorman <mel@csn.ul.ie>,
akpm@linux-foundation.org, Johannes Weiner <hannes@cmpxchg.org>,
hughd@google.com
Subject: Re: [PATCH -mm 2/2] mm: kswapd carefully invoke compaction
Date: Wed, 11 Jan 2012 08:34:06 -0500 [thread overview]
Message-ID: <4F0D8FCE.7080202@redhat.com> (raw)
In-Reply-To: <CAHGf_=rj=aDVGWXqdq7fh_LrCFnug_mPNuuE=YdXaWpvwyjfzg@mail.gmail.com>
On 01/11/2012 02:25 AM, KOSAKI Motohiro wrote:
>> With CONFIG_COMPACTION enabled, kswapd does not try to free
>> contiguous free pages, even when it is woken for a higher order
>> request.
>>
>> This could be bad for eg. jumbo frame network allocations, which
>> are done from interrupt context and cannot compact memory themselves.
>> Higher than before allocation failure rates in the network receive
>> path have been observed in kernels with compaction enabled.
>>
>> Teach kswapd to defragment the memory zones in a node, but only
>> if required and compaction is not deferred in a zone.
>>
>> Signed-off-by: Rik van Riel<riel@redhat.com>
>
> I agree with we need asynchronous defragmentations feature. But, do we
> really need to use kswapd for compaction? While kswapd take a
> compaction work, it can't work to make free memory.
I believe we do need some background compaction, especially
to help allocations from network interrupts.
If you believe the compaction is better done from some
other thread, I guess we could do that, but truthfully, if
kswapd spends a lot of time doing compaction, I made a
mistake somewhere :)
--
All rights reversed
next prev parent reply other threads:[~2012-01-11 13:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-10 2:31 [PATCH -mm 0/2] kswapd vs compaction improvements Rik van Riel
2012-01-10 2:31 ` Rik van Riel
2012-01-10 2:33 ` [PATCH -mm 1/2] mm: kswapd test order 0 watermarks when compaction is enabled Rik van Riel
2012-01-10 2:33 ` Rik van Riel
2012-01-12 15:46 ` Mel Gorman
2012-01-12 15:46 ` Mel Gorman
2012-01-10 2:33 ` [PATCH -mm 2/2] mm: kswapd carefully invoke compaction Rik van Riel
2012-01-10 2:33 ` Rik van Riel
2012-01-11 7:25 ` KOSAKI Motohiro
2012-01-11 7:25 ` KOSAKI Motohiro
2012-01-11 13:34 ` Rik van Riel [this message]
2012-01-11 13:34 ` Rik van Riel
2012-01-11 19:57 ` KOSAKI Motohiro
2012-01-11 19:57 ` KOSAKI Motohiro
2012-01-12 16:12 ` Mel Gorman
2012-01-12 16:12 ` Mel Gorman
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