Re: [PATCH 3/7] mm: rework __isolate_lru_page() file/anon filter

[Konstantin Khlebnikov]

Konstantin Khlebnikov wrote:
> Hugh Dickins wrote:
> > On Wed, 29 Feb 2012, Konstantin Khlebnikov wrote:
> >
> > > This patch adds file/anon filter bits into isolate_mode_t,
> > > this allows to simplify checks in __isolate_lru_page().
> > >
> > > Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
> >
> > Almost-Acked-by: Hugh Dickins<hughd@xxxxxxxxxx>
> >
> > with one whitespace nit, and one functional addition requested.
> >
> > I'm perfectly happy with your :?s myself, but some people do dislike
> > them.  I'm happy with the switch alternative if it's as efficient:
> > something that surprised me very much when trying to get convincing
> > performance numbers for per-memcg per-zone lru_lock at home...
> >
> > ... __isolate_lru_page() featured astonishly high on the perf report
> > of streaming from files on ext4 on /dev/ram0 to /dev/null, coming
> > immediately below the obvious zeroing and copying: okay, the zeroing
> > and copying were around 30% each, and __isolate_lru_page() down around
> > 2% or below, but even so it seemed very odd that it should feature so
> > high, and any optimizations to it very welcome - unless it was purely
> > some bogus result.
>
> Actually ANON/FILE ACTIVE/INACTIVE checks does not required at non-lumpy reclaim
> (all pages are picked from right lru list) and compaction (it does not care).
> But seems like removing these two bit-checks cannot give noticeable performance gain.
>
> This patch can be postponed. It does not so important and
> it does not share context with other patches in this set.

Oops, no it cannot be dropped. Next patch "mm: push lru index into shrink_[in]active_list()"
kills "file" variable in isolate_lru_pages(). I sent v2 for this patch only.

> > > ---
> > >    include/linux/mmzone.h |    4 ++++
> > >    include/linux/swap.h   |    2 +-
> > >    mm/compaction.c        |    5 +++--
> > >    mm/vmscan.c            |   27 +++++++++++++--------------
> > >    4 files changed, 21 insertions(+), 17 deletions(-)
> > >
> > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > > index eff4918..2fed935 100644
> > > --- a/include/linux/mmzone.h
> > > +++ b/include/linux/mmzone.h
> > > @@ -193,6 +193,10 @@ struct lruvec {
> > >    #define ISOLATE_UNMAPPED	((__force isolate_mode_t)0x8)
> > >    /* Isolate for asynchronous migration */
> > >    #define ISOLATE_ASYNC_MIGRATE	((__force isolate_mode_t)0x10)
> > > +/* Isolate swap-backed pages */
> > > +#define	ISOLATE_ANON		((__force isolate_mode_t)0x20)
> > > +/* Isolate file-backed pages */
> > > +#define	ISOLATE_FILE		((__force isolate_mode_t)0x40)
> >
> >    From the patch you can see that the #defines above yours used a
> > space where you have used a tab: better to use a space as above.
> >
> > > @@ -375,7 +376,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
> > >    			mode |= ISOLATE_ASYNC_MIGRATE;
> > >
> > >    		/* Try isolate the page */
> > > -		if (__isolate_lru_page(page, mode, 0) != 0)
> > > +		if (__isolate_lru_page(page, mode) != 0)
> > >    			continue;
> >
> > I thought you were missing something there, but no, that's rather
> > the case you are simplifying.  However...
> >
> > > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > > index af6cfe7..1b70338 100644
> > > --- a/mm/vmscan.c
> > > +++ b/mm/vmscan.c
> > > @@ -1520,6 +1511,10 @@ shrink_inactive_list(unsigned long nr_to_scan, struct mem_cgroup_zone *mz,
> > >    		isolate_mode |= ISOLATE_UNMAPPED;
> > >    	if (!sc->may_writepage)
> > >    		isolate_mode |= ISOLATE_CLEAN;
> > > +	if (file)
> > > +		isolate_mode |= ISOLATE_FILE;
> > > +	else
> > > +		isolate_mode |= ISOLATE_ANON;
> >
> > Above here, under "if (sc->reclaim_mode&   RECLAIM_MODE_LUMPYRECLAIM)",
> > don't you need
> >
> > 		isolate_mode |= ISOLATE_ACTIVE | ISOLATE_FILE | ISOLATE_ANON;
> >
> > now to reproduce the same "all_lru_mode" behaviour as before?
>
> Yes, I missed this. Thanks.
>
> > Hugh
>
> --
> 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>

--
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/