On Thu 31-01-19 18:37:02, Kirill Tkhai wrote: > On path shrink_inactive_list() ---> shrink_page_list() > we allocate stack variables for the statistics twice. > This is completely useless, and this just consumes stack > much more, then we really need. > > The patch kills duplicate stack variables from shrink_page_list(), > and this reduce stack usage and object file size significantly:
significantly is a bit of an overstatement for 32B saved... > Stack usage: > Before: vmscan.c:1122:22:shrink_page_list 648 static > After: vmscan.c:1122:22:shrink_page_list 616 static > > Size of vmscan.o: > text data bss dec hex filename > Before: 56866 4720 128 61714 f112 mm/vmscan.o > After: 56770 4720 128 61618 f0b2 mm/vmscan.o > > Signed-off-by: Kirill Tkhai <[email protected]> Acked-by: Michal Hocko <[email protected]> > --- > mm/vmscan.c | 44 ++++++++++++++------------------------------ > 1 file changed, 14 insertions(+), 30 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index dd9554f5d788..54a389fd91e2 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1128,16 +1128,9 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > { > LIST_HEAD(ret_pages); > LIST_HEAD(free_pages); > - int pgactivate = 0; > - unsigned nr_unqueued_dirty = 0; > - unsigned nr_dirty = 0; > - unsigned nr_congested = 0; > unsigned nr_reclaimed = 0; > - unsigned nr_writeback = 0; > - unsigned nr_immediate = 0; > - unsigned nr_ref_keep = 0; > - unsigned nr_unmap_fail = 0; > > + memset(stat, 0, sizeof(*stat)); > cond_resched(); > > while (!list_empty(page_list)) { > @@ -1181,10 +1174,10 @@ static unsigned long shrink_page_list(struct > list_head *page_list, > */ > page_check_dirty_writeback(page, &dirty, &writeback); > if (dirty || writeback) > - nr_dirty++; > + stat->nr_dirty++; > > if (dirty && !writeback) > - nr_unqueued_dirty++; > + stat->nr_unqueued_dirty++; > > /* > * Treat this page as congested if the underlying BDI is or if > @@ -1196,7 +1189,7 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > if (((dirty || writeback) && mapping && > inode_write_congested(mapping->host)) || > (writeback && PageReclaim(page))) > - nr_congested++; > + stat->nr_congested++; > > /* > * If a page at the tail of the LRU is under writeback, there > @@ -1245,7 +1238,7 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > if (current_is_kswapd() && > PageReclaim(page) && > test_bit(PGDAT_WRITEBACK, &pgdat->flags)) { > - nr_immediate++; > + stat->nr_immediate++; > goto activate_locked; > > /* Case 2 above */ > @@ -1263,7 +1256,7 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > * and it's also appropriate in global reclaim. > */ > SetPageReclaim(page); > - nr_writeback++; > + stat->nr_writeback++; > goto activate_locked; > > /* Case 3 above */ > @@ -1283,7 +1276,7 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > case PAGEREF_ACTIVATE: > goto activate_locked; > case PAGEREF_KEEP: > - nr_ref_keep++; > + stat->nr_ref_keep++; > goto keep_locked; > case PAGEREF_RECLAIM: > case PAGEREF_RECLAIM_CLEAN: > @@ -1348,7 +1341,7 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > if (unlikely(PageTransHuge(page))) > flags |= TTU_SPLIT_HUGE_PMD; > if (!try_to_unmap(page, flags)) { > - nr_unmap_fail++; > + stat->nr_unmap_fail++; > goto activate_locked; > } > } > @@ -1496,7 +1489,7 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > VM_BUG_ON_PAGE(PageActive(page), page); > if (!PageMlocked(page)) { > SetPageActive(page); > - pgactivate++; > + stat->nr_activate++; > count_memcg_page_event(page, PGACTIVATE); > } > keep_locked: > @@ -1511,18 +1504,8 @@ static unsigned long shrink_page_list(struct list_head > *page_list, > free_unref_page_list(&free_pages); > > list_splice(&ret_pages, page_list); > - count_vm_events(PGACTIVATE, pgactivate); > - > - if (stat) { > - stat->nr_dirty = nr_dirty; > - stat->nr_congested = nr_congested; > - stat->nr_unqueued_dirty = nr_unqueued_dirty; > - stat->nr_writeback = nr_writeback; > - stat->nr_immediate = nr_immediate; > - stat->nr_activate = pgactivate; > - stat->nr_ref_keep = nr_ref_keep; > - stat->nr_unmap_fail = nr_unmap_fail; > - } > + count_vm_events(PGACTIVATE, stat->nr_activate); > + > return nr_reclaimed; > } > > @@ -1534,6 +1517,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone > *zone, > .priority = DEF_PRIORITY, > .may_unmap = 1, > }; > + struct reclaim_stat dummy_stat; > unsigned long ret; > struct page *page, *next; > LIST_HEAD(clean_pages); > @@ -1547,7 +1531,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone > *zone, > } > > ret = shrink_page_list(&clean_pages, zone->zone_pgdat, &sc, > - TTU_IGNORE_ACCESS, NULL, true); > + TTU_IGNORE_ACCESS, &dummy_stat, true); > list_splice(&clean_pages, page_list); > mod_node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE, -ret); > return ret; > @@ -1922,7 +1906,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct > lruvec *lruvec, > unsigned long nr_scanned; > unsigned long nr_reclaimed = 0; > unsigned long nr_taken; > - struct reclaim_stat stat = {}; > + struct reclaim_stat stat; > int file = is_file_lru(lru); > struct pglist_data *pgdat = lruvec_pgdat(lruvec); > struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; > -- Michal Hocko SUSE Labs
