On Tue, Apr 26, 2011 at 10:30:59PM +1000, NeilBrown wrote:
> On Tue, 26 Apr 2011 08:36:53 +0100 Mel Gorman <mgorman@xxxxxxx> wrote:
>
>
> > +/*
> > + * Throttle direct reclaimers if backing storage is backed by the network
> > + * and the PFMEMALLOC reserve for the preferred node is getting dangerously
> > + * depleted. kswapd will continue to make progress and wake the processes
> > + * when the low watermark is reached
> > + */
> > +static void throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
> > + nodemask_t *nodemask)
> > +{
> > + struct zone *zone;
> > + int high_zoneidx = gfp_zone(gfp_mask);
> > + DEFINE_WAIT(wait);
> > +
> > + /* Check if the pfmemalloc reserves are ok */
> > + first_zones_zonelist(zonelist, high_zoneidx, NULL, &zone);
> > + prepare_to_wait(&zone->zone_pgdat->pfmemalloc_wait, &wait,
> > + TASK_INTERRUPTIBLE);
> > + if (pfmemalloc_watermark_ok(zone->zone_pgdat, high_zoneidx))
> > + goto out;
> > +
> > + /* Throttle */
> > + do {
> > + schedule();
> > + finish_wait(&zone->zone_pgdat->pfmemalloc_wait, &wait);
> > + prepare_to_wait(&zone->zone_pgdat->pfmemalloc_wait, &wait,
> > + TASK_INTERRUPTIBLE);
> > + } while (!pfmemalloc_watermark_ok(zone->zone_pgdat, high_zoneidx) &&
> > + !fatal_signal_pending(current));
> > +
> > +out:
> > + finish_wait(&zone->zone_pgdat->pfmemalloc_wait, &wait);
> > +}
>
> You are doing an interruptible wait, but only checking for fatal signals.
> So if a non-fatal signal arrives, you will busy-wait.
>
> So I suspect you want TASK_KILLABLE, so just use:
>
> wait_event_killable(zone->zone_pgdat->pfmemalloc_wait,
> pgmemalloc_watermark_ok(zone->zone_pgdata,
> high_zoneidx));
>
Well, if a normal signal arrives, we do not necessarily want the
process to enter reclaim. For fatal signals, I allow it to continue
because it's not likely to be putting the system under more pressure
if it's exiting.
> (You also have an extraneous call to finish_wait)
>
Which one? I'm not seeing a flow where finish_wait gets called twice
without a prepare_to_wait in between.
--
Mel Gorman
SUSE Labs
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxxx For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>