> 在 2019年12月18日，18:47，Yafang Shao <laoar.shao@xxxxxxxxx> 写道： > > On Wed, Dec 18, 2019 at 5:44 PM Hui Zhu <teawaterz@xxxxxxxxxxxxxxxxx> wrote: >> >> Currently, memcg has some config to limit memory usage and config >> the shrink behavior. >> In the memory-constrained environment, put different priority tasks >> into different cgroups with different memory limits to protect the >> performance of the high priority tasks. Because the global memory >> shrink will affect the performance of all tasks. The memory limit >> cgroup can make shrink happen inside the cgroup. Then it can decrease >> the memory shrink of the high priority task to protect its performance. >> >> But the memory footprint of the task is not static. It will change as >> the working pressure changes. And the version changes will affect it too. >> Then set the appropriate memory limit to decrease the global memory shrink >> is a difficult job and lead to wasted memory or performance loss sometimes. >> >> This commit adds global shrink priority to memcg to try to handle this >> problem. >> The default global shrink priority of each cgroup is DEF_PRIORITY. >> Its behavior in global shrink is not changed. >> And when global shrink priority of a cgroup is smaller than DEF_PRIORITY, >> its memory will be shrink when memcg->global_shrink_priority greater than >> or equal to sc->priority. >> > > Just a kind reminder that sc->priority is really propotional, rather > than priority. > The relcaimer scans (total_size >> priority) pages at once. > If the relcaimer can't relaim enough memory, it will decrease > sc->priority and scan MEMCGs again until the sc->pirority drops to 0. > (sc->priority is really a misleading wording. ) > So comparing the memcg priority with sc->priority may cause unexpected issues. > >> The following is an example to use global shrink priority in a VM that >> has 2 CPUs, 1G memory and 4G swap: >> # These are test shells that call usemem that get from >> # https://git.kernel.org/pub/scm/linux/kernel/git/wfg/vm-scalability.git >> cat 1.sh >> sleep 9999 >> # -s 3600: Sleep 3600 seconds after test complete then usemem will >> # not release the memory at once. >> # -Z: read memory again after access the memory. >> # The first time access memory need shrink memory to allocate page. >> # Then the access speed of high priority will not increase a lot. >> # The read again speed of high priority will increase. >> # $((850 * 1024 * 1024 + 8)): Different sizes are used to distinguish >> # the results of the two tests. >> usemem -s 3600 -Z -a -n 1 $((850 * 1024 * 1024 + 8)) >> cat 2.sh >> sleep 9999 >> usemem -s 3600 -Z -a -n 1 $((850 * 1024 * 1024)) >> >> # Setup swap >> swapon /swapfile >> # Setup 2 cgroups >> mkdir /sys/fs/cgroup/memory/t1/ >> mkdir /sys/fs/cgroup/memory/t2/ >> >> # Run tests with same global shrink priority >> cat /sys/fs/cgroup/memory/t1/memory.global_shrink_priority >> 12 >> cat /sys/fs/cgroup/memory/t2/memory.global_shrink_priority >> 12 >> echo $$ > /sys/fs/cgroup/memory/t1/cgroup.procs >> sh 1.sh & >> echo $$ > /sys/fs/cgroup/memory/t2/cgroup.procs >> sh 2.sh & >> echo $$ > /sys/fs/cgroup/memory/cgroup.procs >> killall sleep >> # This the test results >> 1002700800 bytes / 2360359 usecs = 414852 KB/s >> 1002700809 bytes / 2676181 usecs = 365894 KB/s >> read again 891289600 bytes / 13515142 usecs = 64401 KB/s >> read again 891289608 bytes / 13252268 usecs = 65679 KB/s >> killall usemem >> >> # Run tests with 12 and 8 >> cat /sys/fs/cgroup/memory/t1/memory.global_shrink_priority >> 12 >> echo 8 > /sys/fs/cgroup/memory/t2/memory.global_shrink_priority >> echo $$ > /sys/fs/cgroup/memory/t1/cgroup.procs >> sh 1.sh & >> echo $$ > /sys/fs/cgroup/memory/t2/cgroup.procs >> sh 2.sh & >> echo $$ > /sys/fs/cgroup/memory/cgroup.procs >> killall sleep >> # This the test results >> 1002700800 bytes / 1809056 usecs = 541276 KB/s >> 1002700809 bytes / 2184337 usecs = 448282 KB/s >> read again 891289600 bytes / 6666224 usecs = 130568 KB/s >> read again 891289608 bytes / 9171440 usecs = 94903 KB/s >> killall usemem >> >> # This is the test results of 12 and 6 >> 1002700800 bytes / 1827914 usecs = 535692 KB/s >> 1002700809 bytes / 2135124 usecs = 458615 KB/s >> read again 891289600 bytes / 1498419 usecs = 580878 KB/s >> read again 891289608 bytes / 7328362 usecs = 118771 KB/s >> >> Signed-off-by: Hui Zhu <teawaterz@xxxxxxxxxxxxxxxxx> >> --- >> include/linux/memcontrol.h | 2 ++ >> mm/memcontrol.c | 32 ++++++++++++++++++++++++++++++++ >> mm/vmscan.c | 39 ++++++++++++++++++++++++++++++++++++--- >> 3 files changed, 70 insertions(+), 3 deletions(-) >> >> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h >> index a7a0a1a5..8ad2437 100644 >> --- a/include/linux/memcontrol.h >> +++ b/include/linux/memcontrol.h >> @@ -244,6 +244,8 @@ struct mem_cgroup { >> /* OOM-Killer disable */ >> int oom_kill_disable; >> >> + s8 global_shrink_priority; >> + >> /* memory.events and memory.events.local */ >> struct cgroup_file events_file; >> struct cgroup_file events_local_file; >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c >> index c5b5f74..39fdc84 100644 >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -4646,6 +4646,32 @@ static ssize_t memcg_write_event_control(struct kernfs_open_file *of, >> return ret; >> } >> >> +static ssize_t mem_global_shrink_priority_write(struct kernfs_open_file *of, >> + char *buf, size_t nbytes, loff_t off) >> +{ >> + struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of)); >> + s8 val; >> + int ret; >> + >> + ret = kstrtos8(buf, 0, &val); >> + if (ret < 0) >> + return ret; >> + if (val > DEF_PRIORITY) >> + return -EINVAL; >> + >> + memcg->global_shrink_priority = val; >> + >> + return nbytes; >> +} >> + >> +static s64 mem_global_shrink_priority_read(struct cgroup_subsys_state *css, >> + struct cftype *cft) >> +{ >> + struct mem_cgroup *memcg = mem_cgroup_from_css(css); >> + >> + return memcg->global_shrink_priority; >> +} >> + >> static struct cftype mem_cgroup_legacy_files[] = { >> { >> .name = "usage_in_bytes", >> @@ -4774,6 +4800,11 @@ static struct cftype mem_cgroup_legacy_files[] = { >> .write = mem_cgroup_reset, >> .read_u64 = mem_cgroup_read_u64, >> }, >> + { >> + .name = "global_shrink_priority", >> + .write = mem_global_shrink_priority_write, >> + .read_s64 = mem_global_shrink_priority_read, >> + }, >> { }, /* terminate */ >> }; >> >> @@ -4996,6 +5027,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) >> >> memcg->high = PAGE_COUNTER_MAX; >> memcg->soft_limit = PAGE_COUNTER_MAX; >> + memcg->global_shrink_priority = DEF_PRIORITY; >> if (parent) { >> memcg->swappiness = mem_cgroup_swappiness(parent); >> memcg->oom_kill_disable = parent->oom_kill_disable; >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index 74e8edc..5e11d45 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -2637,17 +2637,33 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat, >> return inactive_lru_pages > pages_for_compaction; >> } >> >> +static bool get_is_global_shrink(struct scan_control *sc) >> +{ >> + if (!sc->target_mem_cgroup || >> + mem_cgroup_is_root(sc->target_mem_cgroup)) >> + return true; >> + >> + return false; >> +} >> + >> static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) >> { >> struct mem_cgroup *target_memcg = sc->target_mem_cgroup; >> struct mem_cgroup *memcg; >> + bool is_global_shrink = get_is_global_shrink(sc); >> >> memcg = mem_cgroup_iter(target_memcg, NULL, NULL); >> do { >> - struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat); >> + struct lruvec *lruvec; >> unsigned long reclaimed; >> unsigned long scanned; >> >> + if (is_global_shrink && >> + memcg->global_shrink_priority < sc->priority) >> + continue; >> + >> + lruvec = mem_cgroup_lruvec(memcg, pgdat); >> + >> switch (mem_cgroup_protected(target_memcg, memcg)) { >> case MEMCG_PROT_MIN: >> /* >> @@ -2682,11 +2698,21 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) >> reclaimed = sc->nr_reclaimed; >> scanned = sc->nr_scanned; >> >> + if (is_global_shrink && >> + memcg->global_shrink_priority != DEF_PRIORITY) >> + sc->priority += DEF_PRIORITY >> + - memcg->global_shrink_priority; >> + > > For example. > In this case this memcg can't do full scan. > This behavior is similar with a hard protect(memroy.min), which may > cause unexpected OOM under memory pressure. > > Pls. correct me if I misunderstand you. Thanks and agree with you. Low priority task should do more shrink if the high priority task is ignored. Best, Hui > >> shrink_lruvec(lruvec, sc); >> >> shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, >> sc->priority); >> >> + if (is_global_shrink && >> + memcg->global_shrink_priority != DEF_PRIORITY) >> + sc->priority -= DEF_PRIORITY >> + - memcg->global_shrink_priority; >> + >> /* Record the group's reclaim efficiency */ >> vmpressure(sc->gfp_mask, memcg, false, >> sc->nr_scanned - scanned, >> @@ -3395,11 +3421,18 @@ static void age_active_anon(struct pglist_data *pgdat, >> >> memcg = mem_cgroup_iter(NULL, NULL, NULL); >> do { >> + if (memcg->global_shrink_priority < sc->priority) >> + continue; >> + >> lruvec = mem_cgroup_lruvec(memcg, pgdat); >> + /* >> + * Not set sc->priority according even if this is >> + * a global shrink because nr_to_scan is set to >> + * SWAP_CLUSTER_MAX and there is not other part use it. >> + */ >> shrink_active_list(SWAP_CLUSTER_MAX, lruvec, >> sc, LRU_ACTIVE_ANON); >> - memcg = mem_cgroup_iter(NULL, memcg, NULL); >> - } while (memcg); >> + } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL))); >> } >> >> static bool pgdat_watermark_boosted(pg_data_t *pgdat, int classzone_idx) >> -- >> 2.7.4
