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List:       freebsd-hackers
Subject:    Re: improving VM - questions
From:       Artem Belevich <art () freebsd ! org>
Date:       2012-02-28 23:01:00
Message-ID: CAFqOu6gJp1wA_p9ycXnyx4_YDLm6zvXZC50j=UEaqpmvn70M_A () mail ! gmail ! com
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On Tue, Feb 28, 2012 at 1:06 PM, Wojciech Puchar
<wojtek@wojtek.tensor.gdynia.pl> wrote:
>>>> right. but still 32 pages is 128kB, but i see 64kB I/Os in systat/vmst=
at
>>>
>>> Right, but the comment says to not define MAX_PAGEOUT_CLUSTER to a valu=
e greater
>>> than 32, but you did that. =A0So all bets could be off unless you exami=
ned 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.
> can i increase DFLTPHYS as well as i did with MAXPHYS without problems?

Sorry, I don't have definitive answer to that.

This old post has some related info:
http://lists.freebsd.org/pipermail/freebsd-performance/2008-February/003311=
.html

Even older thread on freebsd-arch also described some concerns:
http://lists.freebsd.org/pipermail/freebsd-arch/2004-January/001590.html

I don't know whether the stuff above still applies to FreeBSD as it is now:

--Artem
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