From: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Subject: mm/vmscan.c: do not allocate duplicate stack variables in shrink_page_list()
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:
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
Link: http://lkml.kernel.org/r/154894900030.5211.12104993874109647641.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 42 +++++++++++++-----------------------------
1 file changed, 13 insertions(+), 29 deletions(-)
--- a/mm/vmscan.c~mm-do-not-allocate-duplicate-stack-variables-in-shrink_page_list
+++ a/mm/vmscan.c
@@ -1106,16 +1106,9 @@ static unsigned long shrink_page_list(st
{
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)) {
@@ -1159,10 +1152,10 @@ static unsigned long shrink_page_list(st
*/
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
@@ -1174,7 +1167,7 @@ static unsigned long shrink_page_list(st
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
@@ -1223,7 +1216,7 @@ static unsigned long shrink_page_list(st
if (current_is_kswapd() &&
PageReclaim(page) &&
test_bit(PGDAT_WRITEBACK, &pgdat->flags)) {
- nr_immediate++;
+ stat->nr_immediate++;
goto activate_locked;
/* Case 2 above */
@@ -1241,7 +1234,7 @@ static unsigned long shrink_page_list(st
* and it's also appropriate in global reclaim.
*/
SetPageReclaim(page);
- nr_writeback++;
+ stat->nr_writeback++;
goto activate_locked;
/* Case 3 above */
@@ -1261,7 +1254,7 @@ static unsigned long shrink_page_list(st
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:
@@ -1326,7 +1319,7 @@ static unsigned long shrink_page_list(st
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;
}
}
@@ -1474,7 +1467,7 @@ activate_locked:
VM_BUG_ON_PAGE(PageActive(page), page);
if (!PageMlocked(page)) {
SetPageActive(page);
- pgactivate++;
+ stat->nr_activate++;
count_memcg_page_event(page, PGACTIVATE);
}
keep_locked:
@@ -1489,18 +1482,8 @@ keep:
free_unref_page_list(&free_pages);
list_splice(&ret_pages, page_list);
- count_vm_events(PGACTIVATE, pgactivate);
+ count_vm_events(PGACTIVATE, stat->nr_activate);
- 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;
- }
return nr_reclaimed;
}
@@ -1512,6 +1495,7 @@ unsigned long reclaim_clean_pages_from_l
.priority = DEF_PRIORITY,
.may_unmap = 1,
};
+ struct reclaim_stat dummy_stat;
unsigned long ret;
struct page *page, *next;
LIST_HEAD(clean_pages);
@@ -1525,7 +1509,7 @@ unsigned long reclaim_clean_pages_from_l
}
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;
@@ -1900,7 +1884,7 @@ shrink_inactive_list(unsigned long nr_to
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;
_
