Messages in this thread | | | Date | Wed, 16 Jul 2003 15:21:39 +0200 | From | Jens Axboe <> | Subject | Re: RFC on io-stalls patch |
| |
On Wed, Jul 16 2003, Andrea Arcangeli wrote: > 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.
That may be so, but no user will ever touch that sysctl. He just experiences what Alan outlined, system grinds to a complete halt. Only much later does it get going again.
-- Jens Axboe
- 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/
| |