Messages in this thread | | | Date | Tue, 27 Feb 2007 21:30:43 -0500 | From | Bill Davidsen <> | Subject | Re: latencies due to disk writes |
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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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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