mm: vmscan: replace shrink_node() loop with a retry jump

Most of the function body is inside a loop, which imposes an additional
indentation and scoping level that makes the code a bit hard to follow and
modify.

The looping only happens in case of reclaim-compaction, which isn't the
common case.  So rather than adding yet another function level to the
reclaim path and have every reclaim invocation go through a level that
only exists for one specific cornercase, use a retry goto.

Link: http://lkml.kernel.org/r/20191022144803.302233-6-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2019-11-30 17:55:43 -08:00 committed by Linus Torvalds
parent b5ead35e7e
commit d2af339706
1 changed files with 116 additions and 117 deletions

View File

@ -2729,144 +2729,143 @@ static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg)
static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
{
struct reclaim_state *reclaim_state = current->reclaim_state;
struct mem_cgroup *root = sc->target_mem_cgroup;
unsigned long nr_reclaimed, nr_scanned;
bool reclaimable = false;
struct mem_cgroup *memcg;
again:
memset(&sc->nr, 0, sizeof(sc->nr));
nr_reclaimed = sc->nr_reclaimed;
nr_scanned = sc->nr_scanned;
memcg = mem_cgroup_iter(root, NULL, NULL);
do {
struct mem_cgroup *root = sc->target_mem_cgroup;
struct mem_cgroup *memcg;
unsigned long reclaimed;
unsigned long scanned;
memset(&sc->nr, 0, sizeof(sc->nr));
nr_reclaimed = sc->nr_reclaimed;
nr_scanned = sc->nr_scanned;
memcg = mem_cgroup_iter(root, NULL, NULL);
do {
unsigned long reclaimed;
unsigned long scanned;
switch (mem_cgroup_protected(root, memcg)) {
case MEMCG_PROT_MIN:
/*
* Hard protection.
* If there is no reclaimable memory, OOM.
*/
switch (mem_cgroup_protected(root, memcg)) {
case MEMCG_PROT_MIN:
/*
* Hard protection.
* If there is no reclaimable memory, OOM.
*/
continue;
case MEMCG_PROT_LOW:
/*
* Soft protection.
* Respect the protection only as long as
* there is an unprotected supply
* of reclaimable memory from other cgroups.
*/
if (!sc->memcg_low_reclaim) {
sc->memcg_low_skipped = 1;
continue;
case MEMCG_PROT_LOW:
/*
* Soft protection.
* Respect the protection only as long as
* there is an unprotected supply
* of reclaimable memory from other cgroups.
*/
if (!sc->memcg_low_reclaim) {
sc->memcg_low_skipped = 1;
continue;
}
memcg_memory_event(memcg, MEMCG_LOW);
break;
case MEMCG_PROT_NONE:
/*
* All protection thresholds breached. We may
* still choose to vary the scan pressure
* applied based on by how much the cgroup in
* question has exceeded its protection
* thresholds (see get_scan_count).
*/
break;
}
reclaimed = sc->nr_reclaimed;
scanned = sc->nr_scanned;
shrink_node_memcg(pgdat, memcg, sc);
shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
sc->priority);
/* Record the group's reclaim efficiency */
vmpressure(sc->gfp_mask, memcg, false,
sc->nr_scanned - scanned,
sc->nr_reclaimed - reclaimed);
} while ((memcg = mem_cgroup_iter(root, memcg, NULL)));
if (reclaim_state) {
sc->nr_reclaimed += reclaim_state->reclaimed_slab;
reclaim_state->reclaimed_slab = 0;
memcg_memory_event(memcg, MEMCG_LOW);
break;
case MEMCG_PROT_NONE:
/*
* All protection thresholds breached. We may
* still choose to vary the scan pressure
* applied based on by how much the cgroup in
* question has exceeded its protection
* thresholds (see get_scan_count).
*/
break;
}
/* Record the subtree's reclaim efficiency */
vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
sc->nr_scanned - nr_scanned,
sc->nr_reclaimed - nr_reclaimed);
reclaimed = sc->nr_reclaimed;
scanned = sc->nr_scanned;
shrink_node_memcg(pgdat, memcg, sc);
if (sc->nr_reclaimed - nr_reclaimed)
reclaimable = true;
shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
sc->priority);
if (current_is_kswapd()) {
/*
* If reclaim is isolating dirty pages under writeback,
* it implies that the long-lived page allocation rate
* is exceeding the page laundering rate. Either the
* global limits are not being effective at throttling
* processes due to the page distribution throughout
* zones or there is heavy usage of a slow backing
* device. The only option is to throttle from reclaim
* context which is not ideal as there is no guarantee
* the dirtying process is throttled in the same way
* balance_dirty_pages() manages.
*
* Once a node is flagged PGDAT_WRITEBACK, kswapd will
* count the number of pages under pages flagged for
* immediate reclaim and stall if any are encountered
* in the nr_immediate check below.
*/
if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
set_bit(PGDAT_WRITEBACK, &pgdat->flags);
/* Record the group's reclaim efficiency */
vmpressure(sc->gfp_mask, memcg, false,
sc->nr_scanned - scanned,
sc->nr_reclaimed - reclaimed);
/*
* Tag a node as congested if all the dirty pages
* scanned were backed by a congested BDI and
* wait_iff_congested will stall.
*/
if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
set_bit(PGDAT_CONGESTED, &pgdat->flags);
} while ((memcg = mem_cgroup_iter(root, memcg, NULL)));
/* Allow kswapd to start writing pages during reclaim.*/
if (sc->nr.unqueued_dirty == sc->nr.file_taken)
set_bit(PGDAT_DIRTY, &pgdat->flags);
if (reclaim_state) {
sc->nr_reclaimed += reclaim_state->reclaimed_slab;
reclaim_state->reclaimed_slab = 0;
}
/*
* If kswapd scans pages marked marked for immediate
* reclaim and under writeback (nr_immediate), it
* implies that pages are cycling through the LRU
* faster than they are written so also forcibly stall.
*/
if (sc->nr.immediate)
congestion_wait(BLK_RW_ASYNC, HZ/10);
}
/* Record the subtree's reclaim efficiency */
vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
sc->nr_scanned - nr_scanned,
sc->nr_reclaimed - nr_reclaimed);
if (sc->nr_reclaimed - nr_reclaimed)
reclaimable = true;
if (current_is_kswapd()) {
/*
* If reclaim is isolating dirty pages under writeback,
* it implies that the long-lived page allocation rate
* is exceeding the page laundering rate. Either the
* global limits are not being effective at throttling
* processes due to the page distribution throughout
* zones or there is heavy usage of a slow backing
* device. The only option is to throttle from reclaim
* context which is not ideal as there is no guarantee
* the dirtying process is throttled in the same way
* balance_dirty_pages() manages.
*
* Once a node is flagged PGDAT_WRITEBACK, kswapd will
* count the number of pages under pages flagged for
* immediate reclaim and stall if any are encountered
* in the nr_immediate check below.
*/
if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
set_bit(PGDAT_WRITEBACK, &pgdat->flags);
/*
* Legacy memcg will stall in page writeback so avoid forcibly
* stalling in wait_iff_congested().
* Tag a node as congested if all the dirty pages
* scanned were backed by a congested BDI and
* wait_iff_congested will stall.
*/
if (cgroup_reclaim(sc) && writeback_throttling_sane(sc) &&
sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
set_memcg_congestion(pgdat, root, true);
if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
set_bit(PGDAT_CONGESTED, &pgdat->flags);
/* Allow kswapd to start writing pages during reclaim.*/
if (sc->nr.unqueued_dirty == sc->nr.file_taken)
set_bit(PGDAT_DIRTY, &pgdat->flags);
/*
* Stall direct reclaim for IO completions if underlying BDIs
* and node is congested. Allow kswapd to continue until it
* starts encountering unqueued dirty pages or cycling through
* the LRU too quickly.
* If kswapd scans pages marked marked for immediate
* reclaim and under writeback (nr_immediate), it
* implies that pages are cycling through the LRU
* faster than they are written so also forcibly stall.
*/
if (!sc->hibernation_mode && !current_is_kswapd() &&
current_may_throttle() && pgdat_memcg_congested(pgdat, root))
wait_iff_congested(BLK_RW_ASYNC, HZ/10);
if (sc->nr.immediate)
congestion_wait(BLK_RW_ASYNC, HZ/10);
}
} while (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
sc));
/*
* Legacy memcg will stall in page writeback so avoid forcibly
* stalling in wait_iff_congested().
*/
if (cgroup_reclaim(sc) && writeback_throttling_sane(sc) &&
sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
set_memcg_congestion(pgdat, root, true);
/*
* Stall direct reclaim for IO completions if underlying BDIs
* and node is congested. Allow kswapd to continue until it
* starts encountering unqueued dirty pages or cycling through
* the LRU too quickly.
*/
if (!sc->hibernation_mode && !current_is_kswapd() &&
current_may_throttle() && pgdat_memcg_congested(pgdat, root))
wait_iff_congested(BLK_RW_ASYNC, HZ/10);
if (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
sc))
goto again;
/*
* Kswapd gives up on balancing particular nodes after too