Messages in this thread | | | Date | Wed, 16 Jul 2003 15:11:28 +0200 | From | Andrea Arcangeli <> | Subject | Re: RFC on io-stalls patch |
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On Wed, Jul 16, 2003 at 03:04:42PM +0200, Jens Axboe wrote: > On Wed, Jul 16 2003, Andrea Arcangeli wrote: > > On Wed, Jul 16, 2003 at 02:46:56PM +0200, Jens Axboe wrote: > > > Well it's a combined problem. Threshold too high on dirty memory, > > > someone doing a read well get stuck flushing out as well. > > > > a pure read not. the write throttling should be per-process, then there > > will be little risk. > > A read from user space, dirtying data along the way.
it doesn't necessairly block on dirty memory. We even _free_ ram clean if needed, exactly because of that. You can raise the amount of _free_ ram up to 99% of the whole ram in your box to be almost guaranteed to never wait on dirty memory freeing. Of course the default tries to optimize for writeback cache and there's a reasonable margin to avoid writing dirty stuff. the sysctl is there for special usages where you want to never block in a read from userspace regardless whatever the state of the system.
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