Re: [PATCH 1/4] vmscan: simplify shrink_inactive_list()
From: Mel Gorman
Date: Thu Apr 15 2010 - 09:15:58 EST
On Thu, Apr 15, 2010 at 07:23:04PM +0900, KOSAKI Motohiro wrote:
> Now, max_scan of shrink_inactive_list() is always passed less than
> SWAP_CLUSTER_MAX. then, we can remove scanning pages loop in it.
> This patch also help stack diet.
>
Yep. I modified bloat-o-meter to work with stacks (imaginatively calling it
stack-o-meter) and got the following. The prereq patches are from
earlier in the thread with the subjects
vmscan: kill prev_priority completely
vmscan: move priority variable into scan_control
It gets
$ stack-o-meter vmlinux-vanilla vmlinux-1-2patchprereq
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-72 (-72)
function old new delta
kswapd 748 676 -72
and with this patch on top
$ stack-o-meter vmlinux-vanilla vmlinux-2-simplfy-shrink
add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-144 (-144)
function old new delta
shrink_zone 1232 1160 -72
kswapd 748 676 -72
X86-32 based config.
> detail
> - remove "while (nr_scanned < max_scan)" loop
> - remove nr_freed (now, we use nr_reclaimed directly)
> - remove nr_scan (now, we use nr_scanned directly)
> - rename max_scan to nr_to_scan
> - pass nr_to_scan into isolate_pages() directly instead
> using SWAP_CLUSTER_MAX
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
I couldn't spot any problems. I'd consider throwing a
WARN_ON(nr_to_scan > SWAP_CLUSTER_MAX) in case some future change breaks
the assumptions but otherwise.
Acked-by: Mel Gorman <mel@xxxxxxxxx>
> ---
> mm/vmscan.c | 190 ++++++++++++++++++++++++++++-------------------------------
> 1 files changed, 89 insertions(+), 101 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index eab6028..4de4029 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1137,16 +1137,22 @@ static int too_many_isolated(struct zone *zone, int file,
> * shrink_inactive_list() is a helper for shrink_zone(). It returns the number
> * of reclaimed pages
> */
> -static unsigned long shrink_inactive_list(unsigned long max_scan,
> +static unsigned long shrink_inactive_list(unsigned long nr_to_scan,
> struct zone *zone, struct scan_control *sc,
> int file)
> {
> LIST_HEAD(page_list);
> struct pagevec pvec;
> - unsigned long nr_scanned = 0;
> + unsigned long nr_scanned;
> unsigned long nr_reclaimed = 0;
> struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc);
> int lumpy_reclaim = 0;
> + struct page *page;
> + unsigned long nr_taken;
> + unsigned long nr_active;
> + unsigned int count[NR_LRU_LISTS] = { 0, };
> + unsigned long nr_anon;
> + unsigned long nr_file;
>
> while (unlikely(too_many_isolated(zone, file, sc))) {
> congestion_wait(BLK_RW_ASYNC, HZ/10);
> @@ -1172,119 +1178,101 @@ static unsigned long shrink_inactive_list(unsigned long max_scan,
>
> lru_add_drain();
> spin_lock_irq(&zone->lru_lock);
> - do {
> - struct page *page;
> - unsigned long nr_taken;
> - unsigned long nr_scan;
> - unsigned long nr_freed;
> - unsigned long nr_active;
> - unsigned int count[NR_LRU_LISTS] = { 0, };
> - int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE;
> - unsigned long nr_anon;
> - unsigned long nr_file;
> -
> - nr_taken = sc->isolate_pages(SWAP_CLUSTER_MAX,
> - &page_list, &nr_scan, sc->order, mode,
> - zone, sc->mem_cgroup, 0, file);
> + nr_taken = sc->isolate_pages(nr_to_scan,
> + &page_list, &nr_scanned, sc->order,
> + lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE,
> + zone, sc->mem_cgroup, 0, file);
>
> - if (scanning_global_lru(sc)) {
> - zone->pages_scanned += nr_scan;
> - if (current_is_kswapd())
> - __count_zone_vm_events(PGSCAN_KSWAPD, zone,
> - nr_scan);
> - else
> - __count_zone_vm_events(PGSCAN_DIRECT, zone,
> - nr_scan);
> - }
> + if (scanning_global_lru(sc)) {
> + zone->pages_scanned += nr_scanned;
> + if (current_is_kswapd())
> + __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned);
> + else
> + __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned);
> + }
>
> - if (nr_taken == 0)
> - goto done;
> + if (nr_taken == 0)
> + goto done;
>
> - nr_active = clear_active_flags(&page_list, count);
> - __count_vm_events(PGDEACTIVATE, nr_active);
> + nr_active = clear_active_flags(&page_list, count);
> + __count_vm_events(PGDEACTIVATE, nr_active);
>
> - __mod_zone_page_state(zone, NR_ACTIVE_FILE,
> - -count[LRU_ACTIVE_FILE]);
> - __mod_zone_page_state(zone, NR_INACTIVE_FILE,
> - -count[LRU_INACTIVE_FILE]);
> - __mod_zone_page_state(zone, NR_ACTIVE_ANON,
> - -count[LRU_ACTIVE_ANON]);
> - __mod_zone_page_state(zone, NR_INACTIVE_ANON,
> - -count[LRU_INACTIVE_ANON]);
> + __mod_zone_page_state(zone, NR_ACTIVE_FILE,
> + -count[LRU_ACTIVE_FILE]);
> + __mod_zone_page_state(zone, NR_INACTIVE_FILE,
> + -count[LRU_INACTIVE_FILE]);
> + __mod_zone_page_state(zone, NR_ACTIVE_ANON,
> + -count[LRU_ACTIVE_ANON]);
> + __mod_zone_page_state(zone, NR_INACTIVE_ANON,
> + -count[LRU_INACTIVE_ANON]);
>
> - nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
> - nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
> - __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
> - __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
> + nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
> + nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
> + __mod_zone_page_state(zone, NR_ISOLATED_ANON, nr_anon);
> + __mod_zone_page_state(zone, NR_ISOLATED_FILE, nr_file);
>
> - reclaim_stat->recent_scanned[0] += nr_anon;
> - reclaim_stat->recent_scanned[1] += nr_file;
> + reclaim_stat->recent_scanned[0] += nr_anon;
> + reclaim_stat->recent_scanned[1] += nr_file;
>
> - spin_unlock_irq(&zone->lru_lock);
> + spin_unlock_irq(&zone->lru_lock);
>
> - nr_scanned += nr_scan;
> - nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
> + nr_reclaimed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC);
> +
> + /*
> + * If we are direct reclaiming for contiguous pages and we do
> + * not reclaim everything in the list, try again and wait
> + * for IO to complete. This will stall high-order allocations
> + * but that should be acceptable to the caller
> + */
> + if (nr_reclaimed < nr_taken && !current_is_kswapd() && lumpy_reclaim) {
> + congestion_wait(BLK_RW_ASYNC, HZ/10);
>
> /*
> - * If we are direct reclaiming for contiguous pages and we do
> - * not reclaim everything in the list, try again and wait
> - * for IO to complete. This will stall high-order allocations
> - * but that should be acceptable to the caller
> + * The attempt at page out may have made some
> + * of the pages active, mark them inactive again.
> */
> - if (nr_freed < nr_taken && !current_is_kswapd() &&
> - lumpy_reclaim) {
> - congestion_wait(BLK_RW_ASYNC, HZ/10);
> -
> - /*
> - * The attempt at page out may have made some
> - * of the pages active, mark them inactive again.
> - */
> - nr_active = clear_active_flags(&page_list, count);
> - count_vm_events(PGDEACTIVATE, nr_active);
> -
> - nr_freed += shrink_page_list(&page_list, sc,
> - PAGEOUT_IO_SYNC);
> - }
> + nr_active = clear_active_flags(&page_list, count);
> + count_vm_events(PGDEACTIVATE, nr_active);
>
> - nr_reclaimed += nr_freed;
> + nr_reclaimed += shrink_page_list(&page_list, sc,
> + PAGEOUT_IO_SYNC);
> + }
>
> - local_irq_disable();
> - if (current_is_kswapd())
> - __count_vm_events(KSWAPD_STEAL, nr_freed);
> - __count_zone_vm_events(PGSTEAL, zone, nr_freed);
> + local_irq_disable();
> + if (current_is_kswapd())
> + __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
> + __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
>
> - spin_lock(&zone->lru_lock);
> - /*
> - * Put back any unfreeable pages.
> - */
> - while (!list_empty(&page_list)) {
> - int lru;
> - page = lru_to_page(&page_list);
> - VM_BUG_ON(PageLRU(page));
> - list_del(&page->lru);
> - if (unlikely(!page_evictable(page, NULL))) {
> - spin_unlock_irq(&zone->lru_lock);
> - putback_lru_page(page);
> - spin_lock_irq(&zone->lru_lock);
> - continue;
> - }
> - SetPageLRU(page);
> - lru = page_lru(page);
> - add_page_to_lru_list(zone, page, lru);
> - if (is_active_lru(lru)) {
> - int file = is_file_lru(lru);
> - reclaim_stat->recent_rotated[file]++;
> - }
> - if (!pagevec_add(&pvec, page)) {
> - spin_unlock_irq(&zone->lru_lock);
> - __pagevec_release(&pvec);
> - spin_lock_irq(&zone->lru_lock);
> - }
> + spin_lock(&zone->lru_lock);
> + /*
> + * Put back any unfreeable pages.
> + */
> + while (!list_empty(&page_list)) {
> + int lru;
> + page = lru_to_page(&page_list);
> + VM_BUG_ON(PageLRU(page));
> + list_del(&page->lru);
> + if (unlikely(!page_evictable(page, NULL))) {
> + spin_unlock_irq(&zone->lru_lock);
> + putback_lru_page(page);
> + spin_lock_irq(&zone->lru_lock);
> + continue;
> }
> - __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
> - __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
> -
> - } while (nr_scanned < max_scan);
> + SetPageLRU(page);
> + lru = page_lru(page);
> + add_page_to_lru_list(zone, page, lru);
> + if (is_active_lru(lru)) {
> + int file = is_file_lru(lru);
> + reclaim_stat->recent_rotated[file]++;
> + }
> + if (!pagevec_add(&pvec, page)) {
> + spin_unlock_irq(&zone->lru_lock);
> + __pagevec_release(&pvec);
> + spin_lock_irq(&zone->lru_lock);
> + }
> + }
> + __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
> + __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
>
> done:
> spin_unlock_irq(&zone->lru_lock);
> --
> 1.6.5.2
>
>
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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