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SubjectRe: latencies due to disk writes
kalium@gmx.de wrote:
> Hello!
>
> I'm experiencing extreme lags during disk writes. I have read somewhere (didn't save the URI, sigh) that this is actually related to bad (non-existing) write io priorities (CFQ only manages file reads).
>
> I could imagine two quick, easy and probably quite effective ways to prevent such lags:
>
> 1.) don't flush buffers to disk at once more than necessary.
>
Actually, in many cases this is just what you do want, to avoid filling
memory with buffered writes and then flushing them on time or memory runout.

Investigate the /proc/sys/vm/dirty_* values.

> 2.) relate CPU niceness to max write buffer fill level (ie. the point where it gets forced to be flushed to disk -- a conservative estimate would be much better than nothing): (100-5*nicelevel)%, ie. writes for processes having nice level 19 are blocked/delayed until the write buffer is below 5%. That way, the accounting is done at a higher and probably easier to access level.
>
> Maybe I'm just talking nonsense, but nonetheless, here are my 2 cents.
>
> Best regards,
> Mark
>
> p.s. please CC me as I'm not subscribed to this list.

--
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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