Re: [PATCH 7/8] mm: vmscan: Immediately reclaim end-of-LRU dirty pages when writeback completes

Mel Gorman
2011-08-02T11:25:28Z

On Mon, Aug 01, 2011 at 12:24:01AM +0900, Minchan Kim wrote:
> On Fri, Jul 22, 2011 at 02:23:19PM +0100, Mel Gorman wrote:
> > On Fri, Jul 22, 2011 at 02:53:48PM +0200, Peter Zijlstra wrote:
> > > On Thu, 2011-07-21 at 17:28 +0100, Mel Gorman wrote:
> > > > When direct reclaim encounters a dirty page, it gets recycled around
> > > > the LRU for another cycle. This patch marks the page PageReclaim
> > > > similar to deactivate_page() so that the page gets reclaimed almost
> > > > immediately after the page gets cleaned. This is to avoid reclaiming
> > > > clean pages that are younger than a dirty page encountered at the
> > > > end of the LRU that might have been something like a use-once page.
> > > >
> > >
> > > > @@ -834,7 +834,15 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> > > > */
> > > > if (page_is_file_cache(page) &&
> > > > (!current_is_kswapd() || priority >= DEF_PRIORITY - 2)) {
> > > > - inc_zone_page_state(page, NR_VMSCAN_WRITE_SKIP);
> > > > + /*
> > > > + * Immediately reclaim when written back.
> > > > + * Similar in principal to deactivate_page()
> > > > + * except we already have the page isolated
> > > > + * and know it's dirty
> > > > + */
> > > > + inc_zone_page_state(page, NR_VMSCAN_INVALIDATE);
> > > > + SetPageReclaim(page);
> > > > +
> > >
> > > I find the invalidate name somewhat confusing. It makes me think we'll
> > > drop the page without writeback, like invalidatepage().
> >
> > I wasn't that happy with it either to be honest but didn't think of a
> > better one at the time. nr_reclaim_deferred?
>
> How about "NR_VMSCAN_IMMEDIATE_RECLAIM" like comment rotate_reclaimable_page?
>

Yeah, I guess. I find it a little misleading because the reclaim does
not happen immediately at the time the counter is incremented but it's
better than "invalidate".

--
Mel Gorman
SUSE Labs