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. > 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 > >
