Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 16 Jul 2003 09:49:31 -0700 | From | Andrew Morton <> | Subject | Re: RFC on io-stalls patch |
| |
Jens Axboe <axboe@suse.de> 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.
Actually it's a read from userspace which allocates a page which goes into direct reclaim which discovers a locked buffer on the tail of the LRU and then waits on it.
And if he's especially unlucky: while he waits, some other process continues to pound more writes into the queue which get merged ahead of the one he's waiting on, up to a point.
(I don't know if 2.6 does much better in this regard. It is supposed to. Has anyone tested for it?)
- 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/
| ![\](/images/icornerr.gif) |