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Date: Tue, 28 Feb 2012 10:06:52 -0800
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From: Artem Belevich <art@freebsd.org>
To: Andriy Gapon <avg@freebsd.org>
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Cc: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>,
	Grzegorz Kulewski <grzegorz@kulewski.pl>, freebsd-hackers@freebsd.org
Subject: Re: improving VM - questions
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On Tue, Feb 28, 2012 at 2:21 AM, Andriy Gapon <avg@freebsd.org> wrote:
> on 28/02/2012 11:43 Wojciech Puchar said the following:
>>>> +++ swap_pager.c =A0 =A0 =A0 =A02012-02-25 13:19:51.000000000 +0100
>>>> @@ -119,7 +119,7 @@
>>>> =A0* The 32-page limit is due to the radix code (kern/subr_blist.c).
>>>> =A0*/
>>>> #ifndef MAX_PAGEOUT_CLUSTER
>>>> -#define MAX_PAGEOUT_CLUSTER 16
>>>> +#define MAX_PAGEOUT_CLUSTER 256
>>>> #endif
>>> [snip]
>>>> but swap_pager.c patch seems not to work. i observe 64kB pageouts, no =
more.
>>>>
>>>> what is wrong in it?
>>>
>>> Could there be a problem because of what the MAX_PAGEOUT_CLUSTER commen=
t says?
>>
>> right. but still 32 pages is 128kB, but i see 64kB I/Os in systat/vmstat
>
> Right, but the comment says to not define MAX_PAGEOUT_CLUSTER to a value =
greater
> than 32, but you did that. =A0So all bets could be off unless you examine=
d the
> code and know exactly what should happen in this case.

I suspect it might be DFLTPHYS that splits disk i/o into 64K blocks on
the driver level.

--Artem

>
>
> --
> Andriy Gapon
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