Re: [PATCH][5/?] count writeback pages in nr_scanned

[Nick Piggin]

Nick Piggin wrote:
> Andrea Arcangeli wrote:
>
> > On Thu, Jan 06, 2005 at 04:19:36PM +1100, Nick Piggin wrote:
> >
> > > This is practically what blk_congestion_wait does when the queue
> > > isn't congested though, isn't it?
> >
> >
> >
> > The fundamental difference that makes it reliable is that:
> >
> > 1) only the I/O we're throttling against will be considered for the
> >    wakeup event, which means only clearing PG_writeback will be
> >    considered eligible for wakeup
> >    Currently _all_ unrelated write I/O was considered eligible
> >    for wakeup events and that could cause spurious oom kills.
>
>
> I'm not entirely convinced. In Rik's case it didn't matter, because
> all his writeout was in the same zone that reclaim was happening
> against (ZONE_NORMAL), so in that case, PG_writeback throttling
> will do exactly the same thing as blk_congestion_wait.
>
> I do like your PG_writeback throttling idea for the other reason
> that it should behave better on NUMA systems with lots of zones
> and lots of disks.

... or Andrew's described fix. I think both would result in pretty
similar behaviour, but Andrew's is probably a bit nicer because it
doesn't require the scanner to have initiated the write.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/