Re: [PATCH -mmotm 3/4] memcg: dirty pages accounting and limitinginfrastructure
From: Andrea Righi
Date: Fri Mar 05 2010 - 17:14:21 EST
On Fri, Mar 05, 2010 at 10:12:34AM +0900, Daisuke Nishimura wrote:
> On Thu, 4 Mar 2010 11:40:14 +0100, Andrea Righi <arighi@xxxxxxxxxxx> wrote:
> > Infrastructure to account dirty pages per cgroup and add dirty limit
> > interfaces in the cgroupfs:
> >
> > - Direct write-out: memory.dirty_ratio, memory.dirty_bytes
> >
> > - Background write-out: memory.dirty_background_ratio, memory.dirty_background_bytes
> >
> > Signed-off-by: Andrea Righi <arighi@xxxxxxxxxxx>
> > ---
> > include/linux/memcontrol.h | 80 ++++++++-
> > mm/memcontrol.c | 420 +++++++++++++++++++++++++++++++++++++++-----
> > 2 files changed, 450 insertions(+), 50 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 1f9b119..cc3421b 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -19,12 +19,66 @@
> >
> > #ifndef _LINUX_MEMCONTROL_H
> > #define _LINUX_MEMCONTROL_H
> > +
> > +#include <linux/writeback.h>
> > #include <linux/cgroup.h>
> > +
> > struct mem_cgroup;
> > struct page_cgroup;
> > struct page;
> > struct mm_struct;
> >
> > +/* Cgroup memory statistics items exported to the kernel */
> > +enum mem_cgroup_page_stat_item {
> > + MEMCG_NR_DIRTYABLE_PAGES,
> > + MEMCG_NR_RECLAIM_PAGES,
> > + MEMCG_NR_WRITEBACK,
> > + MEMCG_NR_DIRTY_WRITEBACK_PAGES,
> > +};
> > +
> > +/* Dirty memory parameters */
> > +struct dirty_param {
> > + int dirty_ratio;
> > + unsigned long dirty_bytes;
> > + int dirty_background_ratio;
> > + unsigned long dirty_background_bytes;
> > +};
> > +
> > +/*
> > + * Statistics for memory cgroup.
> > + */
> > +enum mem_cgroup_stat_index {
> > + /*
> > + * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
> > + */
> > + MEM_CGROUP_STAT_CACHE, /* # of pages charged as cache */
> > + MEM_CGROUP_STAT_RSS, /* # of pages charged as anon rss */
> > + MEM_CGROUP_STAT_FILE_MAPPED, /* # of pages charged as file rss */
> > + MEM_CGROUP_STAT_PGPGIN_COUNT, /* # of pages paged in */
> > + MEM_CGROUP_STAT_PGPGOUT_COUNT, /* # of pages paged out */
> > + MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
> > + MEM_CGROUP_EVENTS, /* incremented at every pagein/pageout */
> > + MEM_CGROUP_STAT_FILE_DIRTY, /* # of dirty pages in page cache */
> > + MEM_CGROUP_STAT_WRITEBACK, /* # of pages under writeback */
> > + MEM_CGROUP_STAT_WRITEBACK_TEMP, /* # of pages under writeback using
> > + temporary buffers */
> > + MEM_CGROUP_STAT_UNSTABLE_NFS, /* # of NFS unstable pages */
> > +
> > + MEM_CGROUP_STAT_NSTATS,
> > +};
> > +
> I must have said it earlier, but I don't think exporting all of these flags
> is a good idea.
> Can you export only mem_cgroup_page_stat_item(of course, need to add MEMCG_NR_FILE_MAPPED)?
> We can translate mem_cgroup_page_stat_item to mem_cgroup_stat_index by simple arithmetic
> if you define MEM_CGROUP_STAT_FILE_MAPPED..MEM_CGROUP_STAT_UNSTABLE_NFS sequentially.
Agreed.
>
> > +/*
> > + * TODO: provide a validation check routine. And retry if validation
> > + * fails.
> > + */
> > +static inline void get_global_dirty_param(struct dirty_param *param)
> > +{
> > + param->dirty_ratio = vm_dirty_ratio;
> > + param->dirty_bytes = vm_dirty_bytes;
> > + param->dirty_background_ratio = dirty_background_ratio;
> > + param->dirty_background_bytes = dirty_background_bytes;
> > +}
> > +
> > #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> > /*
> > * All "charge" functions with gfp_mask should use GFP_KERNEL or
> > @@ -117,6 +171,10 @@ extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
> > extern int do_swap_account;
> > #endif
> >
> > +extern bool mem_cgroup_has_dirty_limit(void);
> > +extern void get_dirty_param(struct dirty_param *param);
> > +extern s64 mem_cgroup_page_stat(enum mem_cgroup_page_stat_item item);
> > +
> > static inline bool mem_cgroup_disabled(void)
> > {
> > if (mem_cgroup_subsys.disabled)
> > @@ -125,7 +183,8 @@ static inline bool mem_cgroup_disabled(void)
> > }
> >
> > extern bool mem_cgroup_oom_called(struct task_struct *task);
> > -void mem_cgroup_update_file_mapped(struct page *page, int val);
> > +void mem_cgroup_update_stat(struct page *page,
> > + enum mem_cgroup_stat_index idx, int val);
> > unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> > gfp_t gfp_mask, int nid,
> > int zid);
> > @@ -300,8 +359,8 @@ mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
> > {
> > }
> >
> > -static inline void mem_cgroup_update_file_mapped(struct page *page,
> > - int val)
> > +static inline void mem_cgroup_update_stat(struct page *page,
> > + enum mem_cgroup_stat_index idx, int val)
> > {
> > }
> >
> > @@ -312,6 +371,21 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> > return 0;
> > }
> >
> > +static inline bool mem_cgroup_has_dirty_limit(void)
> > +{
> > + return false;
> > +}
> > +
> > +static inline void get_dirty_param(struct dirty_param *param)
> > +{
> > + get_global_dirty_param(param);
> > +}
> > +
> > +static inline s64 mem_cgroup_page_stat(enum mem_cgroup_page_stat_item item)
> > +{
> > + return -ENOSYS;
> > +}
> > +
> > #endif /* CONFIG_CGROUP_MEM_CONT */
> >
> > #endif /* _LINUX_MEMCONTROL_H */
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 497b6f7..9842e7b 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -73,28 +73,23 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
> > #define THRESHOLDS_EVENTS_THRESH (7) /* once in 128 */
> > #define SOFTLIMIT_EVENTS_THRESH (10) /* once in 1024 */
> >
> > -/*
> > - * Statistics for memory cgroup.
> > - */
> > -enum mem_cgroup_stat_index {
> > - /*
> > - * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
> > - */
> > - MEM_CGROUP_STAT_CACHE, /* # of pages charged as cache */
> > - MEM_CGROUP_STAT_RSS, /* # of pages charged as anon rss */
> > - MEM_CGROUP_STAT_FILE_MAPPED, /* # of pages charged as file rss */
> > - MEM_CGROUP_STAT_PGPGIN_COUNT, /* # of pages paged in */
> > - MEM_CGROUP_STAT_PGPGOUT_COUNT, /* # of pages paged out */
> > - MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
> > - MEM_CGROUP_EVENTS, /* incremented at every pagein/pageout */
> > -
> > - MEM_CGROUP_STAT_NSTATS,
> > -};
> > -
> > struct mem_cgroup_stat_cpu {
> > s64 count[MEM_CGROUP_STAT_NSTATS];
> > };
> >
> > +/* Per cgroup page statistics */
> > +struct mem_cgroup_page_stat {
> > + enum mem_cgroup_page_stat_item item;
> > + s64 value;
> > +};
> > +
> > +enum {
> > + MEM_CGROUP_DIRTY_RATIO,
> > + MEM_CGROUP_DIRTY_BYTES,
> > + MEM_CGROUP_DIRTY_BACKGROUND_RATIO,
> > + MEM_CGROUP_DIRTY_BACKGROUND_BYTES,
> > +};
> > +
> > /*
> > * per-zone information in memory controller.
> > */
> > @@ -208,6 +203,9 @@ struct mem_cgroup {
> >
> > unsigned int swappiness;
> >
> > + /* control memory cgroup dirty pages */
> > + struct dirty_param dirty_param;
> > +
> > /* set when res.limit == memsw.limit */
> > bool memsw_is_minimum;
> >
> > @@ -1033,6 +1031,156 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
> > return swappiness;
> > }
> >
> > +static bool dirty_param_is_valid(struct dirty_param *param)
> > +{
> > + if (param->dirty_ratio && param->dirty_bytes)
> > + return false;
> > + if (param->dirty_background_ratio && param->dirty_background_bytes)
> > + return false;
> > + return true;
> > +}
> > +
> > +static void
> > +__mem_cgroup_get_dirty_param(struct dirty_param *param, struct mem_cgroup *mem)
> > +{
> > + param->dirty_ratio = mem->dirty_param.dirty_ratio;
> > + param->dirty_bytes = mem->dirty_param.dirty_bytes;
> > + param->dirty_background_ratio = mem->dirty_param.dirty_background_ratio;
> > + param->dirty_background_bytes = mem->dirty_param.dirty_background_bytes;
> > +}
> > +
> > +/*
> > + * get_dirty_param() - get dirty memory parameters of the current memcg
> > + * @param: a structure is filled with the dirty memory settings
> > + *
> > + * The function fills @param with the current memcg dirty memory settings. If
> > + * memory cgroup is disabled or in case of error the structure is filled with
> > + * the global dirty memory settings.
> > + */
> > +void get_dirty_param(struct dirty_param *param)
> > +{
> > + struct mem_cgroup *memcg;
> > +
> > + if (mem_cgroup_disabled()) {
> > + get_global_dirty_param(param);
> > + return;
> > + }
> > + /*
> > + * It's possible that "current" may be moved to other cgroup while we
> > + * access cgroup. But precise check is meaningless because the task can
> > + * be moved after our access and writeback tends to take long time.
> > + * At least, "memcg" will not be freed under rcu_read_lock().
> > + */
> > + while (1) {
> > + rcu_read_lock();
> > + memcg = mem_cgroup_from_task(current);
> > + if (likely(memcg))
> > + __mem_cgroup_get_dirty_param(param, memcg);
> > + else
> > + get_global_dirty_param(param);
> > + rcu_read_unlock();
> > + /*
> > + * Since global and memcg dirty_param are not protected we try
> > + * to speculatively read them and retry if we get inconsistent
> > + * values.
> > + */
> > + if (likely(dirty_param_is_valid(param)))
> > + break;
> > + }
> > +}
> > +
> > +static inline bool mem_cgroup_can_swap(struct mem_cgroup *memcg)
> > +{
> > + if (!do_swap_account)
> > + return nr_swap_pages > 0;
> > + return !memcg->memsw_is_minimum &&
> > + (res_counter_read_u64(&memcg->memsw, RES_LIMIT) > 0);
> > +}
> > +
> > +static s64 mem_cgroup_get_local_page_stat(struct mem_cgroup *memcg,
> > + enum mem_cgroup_page_stat_item item)
> > +{
> > + s64 ret;
> > +
> > + switch (item) {
> > + case MEMCG_NR_DIRTYABLE_PAGES:
> > + ret = res_counter_read_u64(&memcg->res, RES_LIMIT) -
> > + res_counter_read_u64(&memcg->res, RES_USAGE);
> > + /* Translate free memory in pages */
> > + ret >>= PAGE_SHIFT;
> > + ret += mem_cgroup_read_stat(memcg, LRU_ACTIVE_FILE) +
> > + mem_cgroup_read_stat(memcg, LRU_INACTIVE_FILE);
> > + if (mem_cgroup_can_swap(memcg))
> > + ret += mem_cgroup_read_stat(memcg, LRU_ACTIVE_ANON) +
> > + mem_cgroup_read_stat(memcg, LRU_INACTIVE_ANON);
> > + break;
> > + case MEMCG_NR_RECLAIM_PAGES:
> > + ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_FILE_DIRTY) +
> > + mem_cgroup_read_stat(memcg,
> > + MEM_CGROUP_STAT_UNSTABLE_NFS);
> > + break;
> > + case MEMCG_NR_WRITEBACK:
> > + ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_WRITEBACK);
> > + break;
> > + case MEMCG_NR_DIRTY_WRITEBACK_PAGES:
> > + ret = mem_cgroup_read_stat(memcg, MEM_CGROUP_STAT_WRITEBACK) +
> > + mem_cgroup_read_stat(memcg,
> > + MEM_CGROUP_STAT_UNSTABLE_NFS);
> > + break;
> > + default:
> > + BUG_ON(1);
> > + }
> > + return ret;
> > +}
> > +
> > +static int mem_cgroup_page_stat_cb(struct mem_cgroup *mem, void *data)
> > +{
> > + struct mem_cgroup_page_stat *stat = (struct mem_cgroup_page_stat *)data;
> > +
> > + stat->value += mem_cgroup_get_local_page_stat(mem, stat->item);
> > + return 0;
> > +}
> > +
> > +/*
> > + * mem_cgroup_has_dirty_limit() - check if current memcg has local dirty limits
> > + *
> > + * Return true if the current memory cgroup has local dirty memory settings,
> > + * false otherwise.
> > + */
> > +bool mem_cgroup_has_dirty_limit(void)
> > +{
> > + if (mem_cgroup_disabled())
> > + return false;
> > + return mem_cgroup_from_task(current) != NULL;
> > +}
> > +
> > +/*
> > + * mem_cgroup_page_stat() - get memory cgroup file cache statistics
> > + * @item: memory statistic item exported to the kernel
> > + *
> > + * Return the accounted statistic value, or a negative value in case of error.
> > + */
> > +s64 mem_cgroup_page_stat(enum mem_cgroup_page_stat_item item)
> > +{
> > + struct mem_cgroup_page_stat stat = {};
> > + struct mem_cgroup *memcg;
> > +
> > + rcu_read_lock();
> > + memcg = mem_cgroup_from_task(current);
> > + if (memcg) {
> > + /*
> > + * Recursively evaulate page statistics against all cgroup
> > + * under hierarchy tree
> > + */
> > + stat.item = item;
> > + mem_cgroup_walk_tree(memcg, &stat, mem_cgroup_page_stat_cb);
> > + } else
> > + stat.value = -EINVAL;
> > + rcu_read_unlock();
> > +
> > + return stat.value;
> > +}
> > +
> > static int mem_cgroup_count_children_cb(struct mem_cgroup *mem, void *data)
> > {
> > int *val = data;
> > @@ -1275,34 +1423,70 @@ static void record_last_oom(struct mem_cgroup *mem)
> > }
> >
> > /*
> > - * Currently used to update mapped file statistics, but the routine can be
> > - * generalized to update other statistics as well.
> > + * Generalized routine to update file cache's status for memcg.
> > + *
> > + * Before calling this, mapping->tree_lock should be held and preemption is
> > + * disabled. Then, it's guarnteed that the page is not uncharged while we
> > + * access page_cgroup. We can make use of that.
> > */
> IIUC, mapping->tree_lock is held with irq disabled, so I think "mapping->tree_lock
> should be held with irq disabled" would be enouth.
> And, as far as I can see, callers of this function have not ensured this yet in [4/4].
>
> how about:
>
> void mem_cgroup_update_stat_locked(...)
> {
> ...
> }
>
> void mem_cgroup_update_stat_unlocked(mapping, ...)
> {
> spin_lock_irqsave(mapping->tree_lock, ...);
> mem_cgroup_update_stat_locked();
> spin_unlock_irqrestore(...);
> }
So, basically, lock_page_cgroup_migrate() should disable irqs and
unlock_page_cgroup_migrate() should re-enable them, except for updating
MEM_CGROUP_STAT_FILE_MAPPED, where just a lock/unlock_page_cgroup() is
needed. Right?
>
> > -void mem_cgroup_update_file_mapped(struct page *page, int val)
> > +void mem_cgroup_update_stat(struct page *page,
> > + enum mem_cgroup_stat_index idx, int val)
> > {
> I preffer "void mem_cgroup_update_page_stat(struct page *, enum mem_cgroup_page_stat_item, ..)"
> as I said above.
>
> > struct mem_cgroup *mem;
> > struct page_cgroup *pc;
> >
> > + if (mem_cgroup_disabled())
> > + return;
> > pc = lookup_page_cgroup(page);
> > - if (unlikely(!pc))
> > + if (unlikely(!pc) || !PageCgroupUsed(pc))
> > return;
> >
> > - lock_page_cgroup(pc);
> > - mem = pc->mem_cgroup;
> > - if (!mem)
> > - goto done;
> > -
> > - if (!PageCgroupUsed(pc))
> > - goto done;
> > -
> > + lock_page_cgroup_migrate(pc);
> > /*
> > - * Preemption is already disabled. We can use __this_cpu_xxx
> > - */
> > - __this_cpu_add(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED], val);
> > -
> > -done:
> > - unlock_page_cgroup(pc);
> > + * It's guarnteed that this page is never uncharged.
> > + * The only racy problem is moving account among memcgs.
> > + */
> > + switch (idx) {
> > + case MEM_CGROUP_STAT_FILE_MAPPED:
> > + if (val > 0)
> > + SetPageCgroupFileMapped(pc);
> > + else
> > + ClearPageCgroupFileMapped(pc);
> > + break;
> > + case MEM_CGROUP_STAT_FILE_DIRTY:
> > + if (val > 0)
> > + SetPageCgroupDirty(pc);
> > + else
> > + ClearPageCgroupDirty(pc);
> > + break;
> > + case MEM_CGROUP_STAT_WRITEBACK:
> > + if (val > 0)
> > + SetPageCgroupWriteback(pc);
> > + else
> > + ClearPageCgroupWriteback(pc);
> > + break;
> > + case MEM_CGROUP_STAT_WRITEBACK_TEMP:
> > + if (val > 0)
> > + SetPageCgroupWritebackTemp(pc);
> > + else
> > + ClearPageCgroupWritebackTemp(pc);
> > + break;
> > + case MEM_CGROUP_STAT_UNSTABLE_NFS:
> > + if (val > 0)
> > + SetPageCgroupUnstableNFS(pc);
> > + else
> > + ClearPageCgroupUnstableNFS(pc);
> > + break;
> > + default:
> > + BUG();
> > + break;
> > + }
> > + mem = pc->mem_cgroup;
> > + if (likely(mem))
> > + __this_cpu_add(mem->stat->count[idx], val);
> > + unlock_page_cgroup_migrate(pc);
> > }
> > +EXPORT_SYMBOL_GPL(mem_cgroup_update_stat);
> >
> > /*
> > * size of first charge trial. "32" comes from vmscan.c's magic value.
> > @@ -1701,6 +1885,45 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
> > memcg_check_events(mem, pc->page);
> > }
> >
> > +/*
> > + * Update file cache accounted statistics on task migration.
> > + *
> > + * TODO: We don't move charges of file (including shmem/tmpfs) pages for now.
> > + * So, at the moment this function simply returns without updating accounted
> > + * statistics, because we deal only with anonymous pages here.
> > + */
> This function is not unique to task migration. It's called from rmdir() too.
> So this comment isn't needed.
Agreed.
>
> > +static void __mem_cgroup_update_file_stat(struct page_cgroup *pc,
> > + struct mem_cgroup *from, struct mem_cgroup *to)
> > +{
> > + struct page *page = pc->page;
> > +
> > + if (!page_mapped(page) || PageAnon(page))
> > + return;
> > +
> > + if (PageCgroupFileMapped(pc)) {
> > + __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
> > + __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
> > + }
> > + if (PageCgroupDirty(pc)) {
> > + __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_DIRTY]);
> > + __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_DIRTY]);
> > + }
> > + if (PageCgroupWriteback(pc)) {
> > + __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_WRITEBACK]);
> > + __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_WRITEBACK]);
> > + }
> > + if (PageCgroupWritebackTemp(pc)) {
> > + __this_cpu_dec(
> > + from->stat->count[MEM_CGROUP_STAT_WRITEBACK_TEMP]);
> > + __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_WRITEBACK_TEMP]);
> > + }
> > + if (PageCgroupUnstableNFS(pc)) {
> > + __this_cpu_dec(
> > + from->stat->count[MEM_CGROUP_STAT_UNSTABLE_NFS]);
> > + __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_UNSTABLE_NFS]);
> > + }
> > +}
> > +
> > /**
> > * __mem_cgroup_move_account - move account of the page
> > * @pc: page_cgroup of the page.
> > @@ -1721,22 +1944,16 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
> > static void __mem_cgroup_move_account(struct page_cgroup *pc,
> > struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
> > {
> > - struct page *page;
> > -
> > VM_BUG_ON(from == to);
> > VM_BUG_ON(PageLRU(pc->page));
> > VM_BUG_ON(!PageCgroupLocked(pc));
> > VM_BUG_ON(!PageCgroupUsed(pc));
> > VM_BUG_ON(pc->mem_cgroup != from);
> >
> > - page = pc->page;
> > - if (page_mapped(page) && !PageAnon(page)) {
> > - /* Update mapped_file data for mem_cgroup */
> > - preempt_disable();
> > - __this_cpu_dec(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
> > - __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
> > - preempt_enable();
> > - }
> > + preempt_disable();
> > + lock_page_cgroup_migrate(pc);
> > + __mem_cgroup_update_file_stat(pc, from, to);
> > +
> > mem_cgroup_charge_statistics(from, pc, false);
> > if (uncharge)
> > /* This is not "cancel", but cancel_charge does all we need. */
> > @@ -1745,6 +1962,8 @@ static void __mem_cgroup_move_account(struct page_cgroup *pc,
> > /* caller should have done css_get */
> > pc->mem_cgroup = to;
> > mem_cgroup_charge_statistics(to, pc, true);
> > + unlock_page_cgroup_migrate(pc);
> > + preempt_enable();
> Glad to see this cleanup :)
> But, hmm, I don't think preempt_disable/enable() is enough(and bit_spin_lock/unlock()
> does it anyway). lock/unlock_page_cgroup_migrate() can be called under irq context
> (e.g. end_page_writeback()), so I think we must local_irq_disable()/enable() here.
You're right. So, also for this case irqs must be disabled/enabled by
lock/unlock_page_cgroup_migrate(). And again, FILE_MAPPED just needs
lock/unlock_page_cgroup().
Thanks,
-Andrea
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