Re: RFC on io-stalls patch

From: Jeff Garzik (jgarzik@pobox.com)
Date: Sun Jul 13 2003 - 11:45:58 EST


Chris Mason wrote:
> Well, I'd say it's a more common problem to have lots of writes, but it
> is pretty easy to fill the queue with reads.

Well....

* you will usually have more reads than writes
* reads are more dependent than writes, on the whole
* writes are larger due to delays and merging

All this is obviously workload dependent, but it seems like the 60%
common case, at least...

Basically when I hear people talking about lots of writes, that seems to
be downplaying the fact that seeing 20 writes and 2 reads on a queue
does not take into account the userspace applications currently
blocking, waiting to do another read.

        Jeff

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