Messages in this thread |  | | | Date | Sun, 05 Dec 2010 09:04:17 -0500 | | From | Rik van Riel <> | | Subject | Re: [PATCH] writeback: enabling-gate for light dirtied bdi |
| |
On 12/05/2010 01:44 AM, Wu Fengguang wrote: > I noticed that my NFSROOT test system goes slow responding when there > is heavy dd to a local disk. Traces show that the NFSROOT's bdi_limit > is near 0 and many tasks in the system are repeatedly stuck in > balance_dirty_pages(). > > There are two related problems: > > - light dirtiers at one device (more often than not the rootfs) get > heavily impacted by heavy dirtiers on another independent device > > - the light dirtied device does heavy throttling because bdi_limit=0, > and the heavy throttling may in turn withhold its bdi_limit in 0 as > it cannot dirty fast enough to grow up the bdi's proportional weight. > > Fix it by introducing some "low pass" gate, which is a small (<=8MB) > value reserved by others and can be safely "stole" from the current > global dirty margin. It does not need to be big to help the bdi gain > its initial weight.
Makes a lot of sense to me.
Acked-by: Rik van Riel <riel@redhat.com>
-- All rights reversed
|  |