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Date: Mon, 15 Nov 2010 09:16:03 +0000
From: Mel Gorman <mel@....ul.ie>
To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Rik van Riel <riel@...hat.com>,
Johannes Weiner <hannes@...xchg.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mm,vmscan: Convert lumpy_mode into a bitmask
On Sun, Nov 14, 2010 at 02:40:21PM +0900, KOSAKI Motohiro wrote:
> > Currently lumpy_mode is an enum and determines if lumpy reclaim is off,
> > syncronous or asyncronous. In preparation for using compaction instead of
> > lumpy reclaim, this patch converts the flags into a bitmap.
> >
> > Signed-off-by: Mel Gorman <mel@....ul.ie>
> > ---
> > include/trace/events/vmscan.h | 6 +++---
> > mm/vmscan.c | 37 +++++++++++++++++++------------------
> > 2 files changed, 22 insertions(+), 21 deletions(-)
> >
> > diff --git a/include/trace/events/vmscan.h b/include/trace/events/vmscan.h
> > index c255fcc..be76429 100644
> > --- a/include/trace/events/vmscan.h
> > +++ b/include/trace/events/vmscan.h
> > @@ -25,13 +25,13 @@
> >
> > #define trace_reclaim_flags(page, sync) ( \
> > (page_is_file_cache(page) ? RECLAIM_WB_FILE : RECLAIM_WB_ANON) | \
> > - (sync == LUMPY_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC) \
> > + (sync & LUMPY_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC) \
> > )
> >
> > #define trace_shrink_flags(file, sync) ( \
> > - (sync == LUMPY_MODE_SYNC ? RECLAIM_WB_MIXED : \
> > + (sync & LUMPY_MODE_SYNC ? RECLAIM_WB_MIXED : \
> > (file ? RECLAIM_WB_FILE : RECLAIM_WB_ANON)) | \
> > - (sync == LUMPY_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC) \
> > + (sync & LUMPY_MODE_SYNC ? RECLAIM_WB_SYNC : RECLAIM_WB_ASYNC) \
> > )
> >
> > TRACE_EVENT(mm_vmscan_kswapd_sleep,
> > diff --git a/mm/vmscan.c b/mm/vmscan.c
> > index b8a6fdc..ffa438e 100644
> > --- a/mm/vmscan.c
> > +++ b/mm/vmscan.c
> > @@ -51,11 +51,11 @@
> > #define CREATE_TRACE_POINTS
> > #include <trace/events/vmscan.h>
> >
> > -enum lumpy_mode {
> > - LUMPY_MODE_NONE,
> > - LUMPY_MODE_ASYNC,
> > - LUMPY_MODE_SYNC,
> > -};
> > +typedef unsigned __bitwise__ lumpy_mode;
> > +#define LUMPY_MODE_SINGLE ((__force lumpy_mode)0x01u)
> > +#define LUMPY_MODE_ASYNC ((__force lumpy_mode)0x02u)
> > +#define LUMPY_MODE_SYNC ((__force lumpy_mode)0x04u)
> > +#define LUMPY_MODE_CONTIGRECLAIM ((__force lumpy_mode)0x08u)
>
> Please write a comment of description of each bit meaning.
>
Will do.
>
> >
> > struct scan_control {
> > /* Incremented by the number of inactive pages that were scanned */
> > @@ -88,7 +88,7 @@ struct scan_control {
> > * Intend to reclaim enough continuous memory rather than reclaim
> > * enough amount of memory. i.e, mode for high order allocation.
> > */
> > - enum lumpy_mode lumpy_reclaim_mode;
> > + lumpy_mode lumpy_reclaim_mode;
> >
> > /* Which cgroup do we reclaim from */
> > struct mem_cgroup *mem_cgroup;
> > @@ -274,13 +274,13 @@ unsigned long shrink_slab(unsigned long scanned, gfp_t gfp_mask,
> > static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc,
> > bool sync)
> > {
> > - enum lumpy_mode mode = sync ? LUMPY_MODE_SYNC : LUMPY_MODE_ASYNC;
> > + lumpy_mode mode = sync ? LUMPY_MODE_SYNC : LUMPY_MODE_ASYNC;
> >
> > /*
> > * Some reclaim have alredy been failed. No worth to try synchronous
> > * lumpy reclaim.
> > */
> > - if (sync && sc->lumpy_reclaim_mode == LUMPY_MODE_NONE)
> > + if (sync && sc->lumpy_reclaim_mode & LUMPY_MODE_SINGLE)
> > return;
>
> Probaby, we can remove LUMPY_MODE_SINGLE entirely. and this line can be
> change to
>
> if (sync && !(sc->lumpy_reclaim_mode & LUMPY_MODE_CONTIGRECLAIM))
>
I had this initially but I found myself getting confused during development
because I had to recall each time "if it's not contig reclaim, what is it?" -
It could be either compaction or single. I decided to spell it out
because it was easier to understand but I can switch back if necessary.
> btw, LUMPY_MODE_ASYNC can be removed too.
>
Similar reasoning - even though I'm not doing anything with the information,
I found it easier to understand if it was spelled out.
> > /*
> > @@ -288,17 +288,18 @@ static void set_lumpy_reclaim_mode(int priority, struct scan_control *sc,
> > * trouble getting a small set of contiguous pages, we
> > * will reclaim both active and inactive pages.
> > */
> > + sc->lumpy_reclaim_mode = LUMPY_MODE_CONTIGRECLAIM;
> > if (sc->order > PAGE_ALLOC_COSTLY_ORDER)
> > - sc->lumpy_reclaim_mode = mode;
> > + sc->lumpy_reclaim_mode |= mode;
> > else if (sc->order && priority < DEF_PRIORITY - 2)
> > - sc->lumpy_reclaim_mode = mode;
> > + sc->lumpy_reclaim_mode |= mode;
> > else
> > - sc->lumpy_reclaim_mode = LUMPY_MODE_NONE;
> > + sc->lumpy_reclaim_mode = LUMPY_MODE_SINGLE | LUMPY_MODE_ASYNC;
> > }
> >
> > static void disable_lumpy_reclaim_mode(struct scan_control *sc)
> > {
> > - sc->lumpy_reclaim_mode = LUMPY_MODE_NONE;
> > + sc->lumpy_reclaim_mode = LUMPY_MODE_SINGLE | LUMPY_MODE_ASYNC;
> > }
> >
> > static inline int is_page_cache_freeable(struct page *page)
> > @@ -429,7 +430,7 @@ static pageout_t pageout(struct page *page, struct address_space *mapping,
> > * first attempt to free a range of pages fails.
> > */
> > if (PageWriteback(page) &&
> > - sc->lumpy_reclaim_mode == LUMPY_MODE_SYNC)
> > + (sc->lumpy_reclaim_mode & LUMPY_MODE_SYNC))
> > wait_on_page_writeback(page);
> >
> > if (!PageWriteback(page)) {
> > @@ -615,7 +616,7 @@ static enum page_references page_check_references(struct page *page,
> > referenced_page = TestClearPageReferenced(page);
> >
> > /* Lumpy reclaim - ignore references */
> > - if (sc->lumpy_reclaim_mode != LUMPY_MODE_NONE)
> > + if (sc->lumpy_reclaim_mode & LUMPY_MODE_CONTIGRECLAIM)
> > return PAGEREF_RECLAIM;
> >
> > /*
> > @@ -732,7 +733,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
> > * for any page for which writeback has already
> > * started.
> > */
> > - if (sc->lumpy_reclaim_mode == LUMPY_MODE_SYNC &&
> > + if ((sc->lumpy_reclaim_mode & LUMPY_MODE_SYNC) &&
> > may_enter_fs)
> > wait_on_page_writeback(page);
> > else {
> > @@ -1317,7 +1318,7 @@ static inline bool should_reclaim_stall(unsigned long nr_taken,
> > return false;
> >
> > /* Only stall on lumpy reclaim */
> > - if (sc->lumpy_reclaim_mode == LUMPY_MODE_NONE)
> > + if (sc->lumpy_reclaim_mode & LUMPY_MODE_SINGLE)
> > return false;
> >
> > /* If we have relaimed everything on the isolated list, no stall */
> > @@ -1368,7 +1369,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
> > if (scanning_global_lru(sc)) {
> > nr_taken = isolate_pages_global(nr_to_scan,
> > &page_list, &nr_scanned, sc->order,
> > - sc->lumpy_reclaim_mode == LUMPY_MODE_NONE ?
> > + sc->lumpy_reclaim_mode & LUMPY_MODE_SINGLE ?
> > ISOLATE_INACTIVE : ISOLATE_BOTH,
> > zone, 0, file);
> > zone->pages_scanned += nr_scanned;
> > @@ -1381,7 +1382,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
> > } else {
> > nr_taken = mem_cgroup_isolate_pages(nr_to_scan,
> > &page_list, &nr_scanned, sc->order,
> > - sc->lumpy_reclaim_mode == LUMPY_MODE_NONE ?
> > + sc->lumpy_reclaim_mode & LUMPY_MODE_SINGLE ?
> > ISOLATE_INACTIVE : ISOLATE_BOTH,
> > zone, sc->mem_cgroup,
> > 0, file);
> > --
> > 1.7.1
> >
>
>
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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