improving VM - questions

[Artem Belevich]

On Tue, Feb 28, 2012 at 2:21 AM, Andriy Gapon <avg at freebsd.org> wrote:
> on 28/02/2012 11:43 Wojciech Puchar said the following:
>>>> +++ swap_pager.c        2012-02-25 13:19:51.000000000 +0100
>>>> @@ -119,7 +119,7 @@
>>>>  * The 32-page limit is due to the radix code (kern/subr_blist.c).
>>>>  */
>>>> #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 comment 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.  So all bets could be off unless you examined 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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