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SubjectRe: [PATCH 0/3] VM throttling: avoid blocking occasional writers
Andrew Morton wrote:
>> On Wed, 14 Mar 2007 21:42:46 +0900 Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com> wrote:
>>
>> ...
>>
>>
>> -Solution:
>>
>> I consider that all of the dirty pages for the disk have been written
>> back and that the disk is clean if a process cannot write 'write_chunk'
>> pages in balance_dirty_pages().
>>
>> To avoid using up the free memory with dirty pages by passing blocking,
>> this patchset adds a new threshold named vm.dirty_limit_ratio to sysctl.
>>
>> It modifies balance_dirty_pages() not to block when the amount of
>> Dirty+Writeback is less than vm.dirty_limit_ratio percent of the memory.
>> In the other cases, writers are throttled as current Linux does.
>>
>>
>> In this patchset, vm.dirty_limit_ratio, instead of vm.dirty_ratio, is
>> used as the clamping level of Dirty+Writeback. And, vm.dirty_ratio is
>> used as the level at which a writers will itself start writeback of the
>> dirty pages.
>
> Might be a reasonable solution - let's see what Peter comes up with too.
>
> Comments on the patch:
>
> - Please don't VM_DIRTY_LIMIT_RATIO: just use CTL_UNNUMBERED and leave
> sysctl.h alone.
>
> - The 40% default is already too high. Let's set this new upper limit to
> 40% and decrease he non-blocking ratio.
>
> - Please update the procfs documentation in ./Docmentation/
>
> - I wonder if dirty_limit_ratio is the best name we could choose.
> vm_dirty_blocking_ratio, perhaps? Dunno.
>
I don't like it, but I dislike it less than "dirty_limit_ratio" I guess.
It would probably break things to change it now, including my
sysctl.conf on a number of systems :-(

--
Bill Davidsen <davidsen@tmr.com>
"We have more to fear from the bungling of the incompetent than from
the machinations of the wicked." - from Slashdot
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