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From: Nick Piggin <piggin@cyberone.com.au>
To: Andrew Morton <akpm@osdl.org>
Cc: Marcelo Tosatti <marcelo.tosatti@cyclades.com>, linux-mm@kvack.org
Subject: Re: [PATCH] kswapd shall not sleep during page shortage
Date: Wed, 10 Nov 2004 11:56:59 +1100	[thread overview]
Message-ID: <4191675B.3090903@cyberone.com.au> (raw)
In-Reply-To: <20041109142257.1d1411e1.akpm@osdl.org>


Andrew Morton wrote:

>Marcelo Tosatti <marcelo.tosatti@cyclades.com> wrote:
>
>
>>Does it makes sense to you?
>>
>
>Maybe.  We really shouldn't be sending kswapd into a busy loop if all zones
>are unreclaimable.  Because it could just be that there's some disk I/O in
>flight and we'll find rotated reclaimable pages available once that I/O has
>completed.  (example: all of memory becomes dirty due to a large msync of
>MAP_SHARED memory).  So rather than madly scanning, we should throttle
>kswapd to make it wait for I/O completions.  Via blk_congestion_wait(). 
>That's what the total_scanned logic is supposed to do.
>
>
>

I think the patch is possibly not a good idea. Unless it fixes up
those #*%! allocation failures (*).

For OOM conditions, kswapd can be a bit lax precisely because it
doesn't oom kill things. If there is a shortage, and kswapd can't
make progress though, I think it really should sleep rather than busy
wait (albiet nicely with cond_resched()).

(*) I'm beginning to think they're due to me accidentally bumping the
    page watermarks when 'fixing' them. I'll check that out presently.

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  parent reply	other threads:[~2004-11-10  0:56 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-11-09 16:46 [PATCH] kswapd shall not sleep during page shortage Marcelo Tosatti
2004-11-09 20:19 ` Andrew Morton
2004-11-09 17:41   ` Marcelo Tosatti
2004-11-09 21:33     ` Andrew Morton
2004-11-09 18:26       ` Marcelo Tosatti
2004-11-09 22:22         ` Andrew Morton
2004-11-09 20:31           ` Marcelo Tosatti
2004-11-10  0:28             ` Andrew Morton
2004-11-09 23:16               ` Marcelo Tosatti
2004-11-09 23:34                 ` Marcelo Tosatti
2004-11-10  2:53                 ` Andrew Morton
2004-11-10 18:14               ` Marcelo Tosatti
2004-11-10 22:08                 ` Andrew Morton
2004-11-10  0:56           ` Nick Piggin [this message]
2004-11-10  2:49             ` Nick Piggin
2004-11-10  2:56               ` Andrew Morton
2004-11-10  3:12                 ` Nick Piggin
2004-11-10  3:18                   ` Andrew Morton
2004-11-10  3:27                     ` Nick Piggin
2004-11-10  4:15                     ` Nick Piggin
2004-11-10  8:17                       ` Marcelo Tosatti

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