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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
Linus Torvalds
parent
b5ead35e7e
commit
d2af339706
233
mm/vmscan.c
233
mm/vmscan.c
@ -2729,144 +2729,143 @@ static bool pgdat_memcg_congested(pg_data_t *pgdat, struct mem_cgroup *memcg)
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static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
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{
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struct reclaim_state *reclaim_state = current->reclaim_state;
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struct mem_cgroup *root = sc->target_mem_cgroup;
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unsigned long nr_reclaimed, nr_scanned;
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bool reclaimable = false;
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struct mem_cgroup *memcg;
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again:
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memset(&sc->nr, 0, sizeof(sc->nr));
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nr_reclaimed = sc->nr_reclaimed;
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nr_scanned = sc->nr_scanned;
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memcg = mem_cgroup_iter(root, NULL, NULL);
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do {
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struct mem_cgroup *root = sc->target_mem_cgroup;
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struct mem_cgroup *memcg;
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unsigned long reclaimed;
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unsigned long scanned;
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memset(&sc->nr, 0, sizeof(sc->nr));
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nr_reclaimed = sc->nr_reclaimed;
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nr_scanned = sc->nr_scanned;
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memcg = mem_cgroup_iter(root, NULL, NULL);
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do {
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unsigned long reclaimed;
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unsigned long scanned;
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switch (mem_cgroup_protected(root, memcg)) {
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case MEMCG_PROT_MIN:
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/*
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* Hard protection.
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* If there is no reclaimable memory, OOM.
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*/
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switch (mem_cgroup_protected(root, memcg)) {
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case MEMCG_PROT_MIN:
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/*
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* Hard protection.
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* If there is no reclaimable memory, OOM.
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*/
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continue;
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case MEMCG_PROT_LOW:
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/*
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* Soft protection.
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* Respect the protection only as long as
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* there is an unprotected supply
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* of reclaimable memory from other cgroups.
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*/
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if (!sc->memcg_low_reclaim) {
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sc->memcg_low_skipped = 1;
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continue;
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case MEMCG_PROT_LOW:
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/*
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* Soft protection.
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* Respect the protection only as long as
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* there is an unprotected supply
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* of reclaimable memory from other cgroups.
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*/
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if (!sc->memcg_low_reclaim) {
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sc->memcg_low_skipped = 1;
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continue;
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}
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memcg_memory_event(memcg, MEMCG_LOW);
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break;
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case MEMCG_PROT_NONE:
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/*
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* All protection thresholds breached. We may
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* still choose to vary the scan pressure
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* applied based on by how much the cgroup in
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* question has exceeded its protection
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* thresholds (see get_scan_count).
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*/
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break;
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}
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reclaimed = sc->nr_reclaimed;
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scanned = sc->nr_scanned;
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shrink_node_memcg(pgdat, memcg, sc);
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shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
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sc->priority);
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/* Record the group's reclaim efficiency */
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vmpressure(sc->gfp_mask, memcg, false,
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sc->nr_scanned - scanned,
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sc->nr_reclaimed - reclaimed);
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} while ((memcg = mem_cgroup_iter(root, memcg, NULL)));
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if (reclaim_state) {
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sc->nr_reclaimed += reclaim_state->reclaimed_slab;
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reclaim_state->reclaimed_slab = 0;
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memcg_memory_event(memcg, MEMCG_LOW);
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break;
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case MEMCG_PROT_NONE:
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/*
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* All protection thresholds breached. We may
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* still choose to vary the scan pressure
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* applied based on by how much the cgroup in
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* question has exceeded its protection
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* thresholds (see get_scan_count).
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*/
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break;
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}
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/* Record the subtree's reclaim efficiency */
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vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
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sc->nr_scanned - nr_scanned,
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sc->nr_reclaimed - nr_reclaimed);
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reclaimed = sc->nr_reclaimed;
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scanned = sc->nr_scanned;
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shrink_node_memcg(pgdat, memcg, sc);
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if (sc->nr_reclaimed - nr_reclaimed)
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reclaimable = true;
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shrink_slab(sc->gfp_mask, pgdat->node_id, memcg,
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sc->priority);
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if (current_is_kswapd()) {
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/*
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* If reclaim is isolating dirty pages under writeback,
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* it implies that the long-lived page allocation rate
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* is exceeding the page laundering rate. Either the
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* global limits are not being effective at throttling
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* processes due to the page distribution throughout
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* zones or there is heavy usage of a slow backing
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* device. The only option is to throttle from reclaim
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* context which is not ideal as there is no guarantee
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* the dirtying process is throttled in the same way
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* balance_dirty_pages() manages.
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*
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* Once a node is flagged PGDAT_WRITEBACK, kswapd will
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* count the number of pages under pages flagged for
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* immediate reclaim and stall if any are encountered
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* in the nr_immediate check below.
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*/
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if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
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set_bit(PGDAT_WRITEBACK, &pgdat->flags);
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/* Record the group's reclaim efficiency */
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vmpressure(sc->gfp_mask, memcg, false,
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sc->nr_scanned - scanned,
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sc->nr_reclaimed - reclaimed);
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/*
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* Tag a node as congested if all the dirty pages
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* scanned were backed by a congested BDI and
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* wait_iff_congested will stall.
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*/
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if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
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set_bit(PGDAT_CONGESTED, &pgdat->flags);
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} while ((memcg = mem_cgroup_iter(root, memcg, NULL)));
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/* Allow kswapd to start writing pages during reclaim.*/
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if (sc->nr.unqueued_dirty == sc->nr.file_taken)
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set_bit(PGDAT_DIRTY, &pgdat->flags);
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if (reclaim_state) {
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sc->nr_reclaimed += reclaim_state->reclaimed_slab;
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reclaim_state->reclaimed_slab = 0;
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}
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/*
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* If kswapd scans pages marked marked for immediate
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* reclaim and under writeback (nr_immediate), it
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* implies that pages are cycling through the LRU
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* faster than they are written so also forcibly stall.
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*/
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if (sc->nr.immediate)
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congestion_wait(BLK_RW_ASYNC, HZ/10);
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}
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/* Record the subtree's reclaim efficiency */
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vmpressure(sc->gfp_mask, sc->target_mem_cgroup, true,
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sc->nr_scanned - nr_scanned,
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sc->nr_reclaimed - nr_reclaimed);
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if (sc->nr_reclaimed - nr_reclaimed)
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reclaimable = true;
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if (current_is_kswapd()) {
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/*
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* If reclaim is isolating dirty pages under writeback,
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* it implies that the long-lived page allocation rate
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* is exceeding the page laundering rate. Either the
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* global limits are not being effective at throttling
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* processes due to the page distribution throughout
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* zones or there is heavy usage of a slow backing
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* device. The only option is to throttle from reclaim
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* context which is not ideal as there is no guarantee
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* the dirtying process is throttled in the same way
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* balance_dirty_pages() manages.
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*
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* Once a node is flagged PGDAT_WRITEBACK, kswapd will
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* count the number of pages under pages flagged for
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* immediate reclaim and stall if any are encountered
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* in the nr_immediate check below.
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*/
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if (sc->nr.writeback && sc->nr.writeback == sc->nr.taken)
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set_bit(PGDAT_WRITEBACK, &pgdat->flags);
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/*
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* Legacy memcg will stall in page writeback so avoid forcibly
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* stalling in wait_iff_congested().
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* Tag a node as congested if all the dirty pages
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* scanned were backed by a congested BDI and
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* wait_iff_congested will stall.
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*/
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if (cgroup_reclaim(sc) && writeback_throttling_sane(sc) &&
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sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
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set_memcg_congestion(pgdat, root, true);
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if (sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
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set_bit(PGDAT_CONGESTED, &pgdat->flags);
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/* Allow kswapd to start writing pages during reclaim.*/
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if (sc->nr.unqueued_dirty == sc->nr.file_taken)
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set_bit(PGDAT_DIRTY, &pgdat->flags);
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/*
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* Stall direct reclaim for IO completions if underlying BDIs
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* and node is congested. Allow kswapd to continue until it
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* starts encountering unqueued dirty pages or cycling through
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* the LRU too quickly.
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* If kswapd scans pages marked marked for immediate
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* reclaim and under writeback (nr_immediate), it
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* implies that pages are cycling through the LRU
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* faster than they are written so also forcibly stall.
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*/
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if (!sc->hibernation_mode && !current_is_kswapd() &&
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current_may_throttle() && pgdat_memcg_congested(pgdat, root))
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wait_iff_congested(BLK_RW_ASYNC, HZ/10);
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if (sc->nr.immediate)
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congestion_wait(BLK_RW_ASYNC, HZ/10);
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}
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} while (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
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sc));
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/*
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* Legacy memcg will stall in page writeback so avoid forcibly
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* stalling in wait_iff_congested().
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*/
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if (cgroup_reclaim(sc) && writeback_throttling_sane(sc) &&
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sc->nr.dirty && sc->nr.dirty == sc->nr.congested)
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set_memcg_congestion(pgdat, root, true);
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/*
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* Stall direct reclaim for IO completions if underlying BDIs
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* and node is congested. Allow kswapd to continue until it
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* starts encountering unqueued dirty pages or cycling through
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* the LRU too quickly.
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*/
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if (!sc->hibernation_mode && !current_is_kswapd() &&
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current_may_throttle() && pgdat_memcg_congested(pgdat, root))
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wait_iff_congested(BLK_RW_ASYNC, HZ/10);
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if (should_continue_reclaim(pgdat, sc->nr_reclaimed - nr_reclaimed,
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sc))
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goto again;
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/*
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* Kswapd gives up on balancing particular nodes after too
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