2. Uncharge
a page/swp_entry may be uncharged (usage -= PAGE_SIZE) by
- mem_cgroup_uncharge_page()
- Called when an anonymous page is fully unmapped. I.e., mapcount goes
- to 0. If the page is SwapCache, uncharge is delayed until
- mem_cgroup_uncharge_swapcache().
-
- mem_cgroup_uncharge_cache_page()
- Called when a page-cache is deleted from radix-tree. If the page is
- SwapCache, uncharge is delayed until mem_cgroup_uncharge_swapcache().
-
- mem_cgroup_uncharge_swapcache()
- Called when SwapCache is removed from radix-tree. The charge itself
- is moved to swap_cgroup. (If mem+swap controller is disabled, no
- charge to swap occurs.)
+ mem_cgroup_uncharge()
+ Called when a page's refcount goes down to 0.
mem_cgroup_uncharge_swap()
Called when swp_entry's refcnt goes down to 0. A charge against swap
disappears.
- mem_cgroup_end_migration(old, new)
- At success of migration old is uncharged (if necessary), a charge
- to new page is committed. At failure, charge to old page is committed.
-
3. charge-commit-cancel
Memcg pages are charged in two steps:
mem_cgroup_try_charge()
Anonymous page is newly allocated at
- page fault into MAP_ANONYMOUS mapping.
- Copy-On-Write.
- It is charged right after it's allocated before doing any page table
- related operations. Of course, it's uncharged when another page is used
- for the fault address.
-
- At freeing anonymous page (by exit() or munmap()), zap_pte() is called
- and pages for ptes are freed one by one.(see mm/memory.c). Uncharges
- are done at page_remove_rmap() when page_mapcount() goes down to 0.
-
- Another page freeing is by page-reclaim (vmscan.c) and anonymous
- pages are swapped out. In this case, the page is marked as
- PageSwapCache(). uncharge() routine doesn't uncharge the page marked
- as SwapCache(). It's delayed until __delete_from_swap_cache().
4.1 Swap-in.
At swap-in, the page is taken from swap-cache. There are 2 cases.
(b) If the SwapCache has been mapped by processes, it has been
charged already.
- This swap-in is one of the most complicated work. In do_swap_page(),
- following events occur when pte is unchanged.
-
- (1) the page (SwapCache) is looked up.
- (2) lock_page()
- (3) try_charge_swapin()
- (4) reuse_swap_page() (may call delete_swap_cache())
- (5) commit_charge_swapin()
- (6) swap_free().
-
- Considering following situation for example.
-
- (A) The page has not been charged before (2) and reuse_swap_page()
- doesn't call delete_from_swap_cache().
- (B) The page has not been charged before (2) and reuse_swap_page()
- calls delete_from_swap_cache().
- (C) The page has been charged before (2) and reuse_swap_page() doesn't
- call delete_from_swap_cache().
- (D) The page has been charged before (2) and reuse_swap_page() calls
- delete_from_swap_cache().
-
- memory.usage/memsw.usage changes to this page/swp_entry will be
- Case (A) (B) (C) (D)
- Event
- Before (2) 0/ 1 0/ 1 1/ 1 1/ 1
- ===========================================
- (3) +1/+1 +1/+1 +1/+1 +1/+1
- (4) - 0/ 0 - -1/ 0
- (5) 0/-1 0/ 0 -1/-1 0/ 0
- (6) - 0/-1 - 0/-1
- ===========================================
- Result 1/ 1 1/ 1 1/ 1 1/ 1
-
- In any cases, charges to this page should be 1/ 1.
-
4.2 Swap-out.
At swap-out, typical state transition is below.
swp_entry's refcnt -= 1.
- At (b), the page is marked as SwapCache and not uncharged.
- At (d), the page is removed from SwapCache and a charge in page_cgroup
- is moved to swap_cgroup.
-
Finally, at task exit,
(e) zap_pte() is called and swp_entry's refcnt -=1 -> 0.
- Here, a charge in swap_cgroup disappears.
5. Page Cache
Page Cache is charged at
- add_to_page_cache_locked().
- uncharged at
- - __remove_from_page_cache().
-
The logic is very clear. (About migration, see below)
Note: __remove_from_page_cache() is called by remove_from_page_cache()
and __remove_mapping().
6. Shmem(tmpfs) Page Cache
- Memcg's charge/uncharge have special handlers of shmem. The best way
- to understand shmem's page state transition is to read mm/shmem.c.
+ The best way to understand shmem's page state transition is to read
+ mm/shmem.c.
But brief explanation of the behavior of memcg around shmem will be
helpful to understand the logic.
It's charged when...
- A new page is added to shmem's radix-tree.
- A swp page is read. (move a charge from swap_cgroup to page_cgroup)
- It's uncharged when
- - A page is removed from radix-tree and not SwapCache.
- - When SwapCache is removed, a charge is moved to swap_cgroup.
- - When swp_entry's refcnt goes down to 0, a charge in swap_cgroup
- disappears.
7. Page Migration
- One of the most complicated functions is page-migration-handler.
- Memcg has 2 routines. Assume that we are migrating a page's contents
- from OLDPAGE to NEWPAGE.
-
- Usual migration logic is..
- (a) remove the page from LRU.
- (b) allocate NEWPAGE (migration target)
- (c) lock by lock_page().
- (d) unmap all mappings.
- (e-1) If necessary, replace entry in radix-tree.
- (e-2) move contents of a page.
- (f) map all mappings again.
- (g) pushback the page to LRU.
- (-) OLDPAGE will be freed.
-
- Before (g), memcg should complete all necessary charge/uncharge to
- NEWPAGE/OLDPAGE.
-
- The point is....
- - If OLDPAGE is anonymous, all charges will be dropped at (d) because
- try_to_unmap() drops all mapcount and the page will not be
- SwapCache.
-
- - If OLDPAGE is SwapCache, charges will be kept at (g) because
- __delete_from_swap_cache() isn't called at (e-1)
-
- - If OLDPAGE is page-cache, charges will be kept at (g) because
- remove_from_swap_cache() isn't called at (e-1)
-
- memcg provides following hooks.
-
- - mem_cgroup_prepare_migration(OLDPAGE)
- Called after (b) to account a charge (usage += PAGE_SIZE) against
- memcg which OLDPAGE belongs to.
-
- - mem_cgroup_end_migration(OLDPAGE, NEWPAGE)
- Called after (f) before (g).
- If OLDPAGE is used, commit OLDPAGE again. If OLDPAGE is already
- charged, a charge by prepare_migration() is automatically canceled.
- If NEWPAGE is used, commit NEWPAGE and uncharge OLDPAGE.
-
- But zap_pte() (by exit or munmap) can be called while migration,
- we have to check if OLDPAGE/NEWPAGE is a valid page after commit().
+
+ mem_cgroup_migrate()
8. LRU
Each memcg has its own private LRU. Now, its handling is under global
return val;
}
-static void mem_cgroup_swap_statistics(struct mem_cgroup *memcg,
- bool charge)
-{
- int val = (charge) ? 1 : -1;
- this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_SWAP], val);
-}
-
static unsigned long mem_cgroup_read_events(struct mem_cgroup *memcg,
enum mem_cgroup_events_index idx)
{
static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
struct page *page,
- bool anon, int nr_pages)
+ int nr_pages)
{
/*
* Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
* counted as CACHE even if it's on ANON LRU.
*/
- if (anon)
+ if (PageAnon(page))
__this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
nr_pages);
else
return lruvec;
}
-/*
- * Following LRU functions are allowed to be used without PCG_LOCK.
- * Operations are called by routine of global LRU independently from memcg.
- * What we have to take care of here is validness of pc->mem_cgroup.
- *
- * Changes to pc->mem_cgroup happens when
- * 1. charge
- * 2. moving account
- * In typical case, "charge" is done before add-to-lru. Exception is SwapCache.
- * It is added to LRU before charge.
- * If PCG_USED bit is not set, page_cgroup is not added to this private LRU.
- * When moving account, the page is not on LRU. It's isolated.
- */
-
/**
* mem_cgroup_page_lruvec - return lruvec for adding an lru page
* @page: the page
*
* Notes: Race condition
*
- * We usually use lock_page_cgroup() for accessing page_cgroup member but
- * it tends to be costly. But considering some conditions, we doesn't need
- * to do so _always_.
+ * Charging occurs during page instantiation, while the page is
+ * unmapped and locked in page migration, or while the page table is
+ * locked in THP migration. No race is possible.
*
- * Considering "charge", lock_page_cgroup() is not required because all
- * file-stat operations happen after a page is attached to radix-tree. There
- * are no race with "charge".
+ * Uncharge happens to pages with zero references, no race possible.
*
- * Considering "uncharge", we know that memcg doesn't clear pc->mem_cgroup
- * at "uncharge" intentionally. So, we always see valid pc->mem_cgroup even
- * if there are race with "uncharge". Statistics itself is properly handled
- * by flags.
- *
- * Considering "move", this is an only case we see a race. To make the race
- * small, we check memcg->moving_account and detect there are possibility
- * of race or not. If there is, we take a lock.
+ * Charge moving between groups is protected by checking mm->moving
+ * account and taking the move_lock in the slowpath.
*/
void __mem_cgroup_begin_update_page_stat(struct page *page,
return mem_cgroup_from_id(id);
}
+/*
+ * try_get_mem_cgroup_from_page - look up page's memcg association
+ * @page: the page
+ *
+ * Look up, get a css reference, and return the memcg that owns @page.
+ *
+ * The page must be locked to prevent racing with swap-in and page
+ * cache charges. If coming from an unlocked page table, the caller
+ * must ensure the page is on the LRU or this can race with charging.
+ */
struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
{
struct mem_cgroup *memcg = NULL;
VM_BUG_ON_PAGE(!PageLocked(page), page);
pc = lookup_page_cgroup(page);
- lock_page_cgroup(pc);
if (PageCgroupUsed(pc)) {
memcg = pc->mem_cgroup;
if (memcg && !css_tryget_online(&memcg->css))
memcg = NULL;
rcu_read_unlock();
}
- unlock_page_cgroup(pc);
return memcg;
}
static void commit_charge(struct page *page, struct mem_cgroup *memcg,
- unsigned int nr_pages, bool anon, bool lrucare)
+ unsigned int nr_pages, bool lrucare)
{
struct page_cgroup *pc = lookup_page_cgroup(page);
struct zone *uninitialized_var(zone);
struct lruvec *lruvec;
bool was_on_lru = false;
- lock_page_cgroup(pc);
VM_BUG_ON_PAGE(PageCgroupUsed(pc), page);
/*
* we don't need page_cgroup_lock about tail pages, becase they are not
}
}
+ /*
+ * Nobody should be changing or seriously looking at
+ * pc->mem_cgroup and pc->flags at this point:
+ *
+ * - the page is uncharged
+ *
+ * - the page is off-LRU
+ *
+ * - an anonymous fault has exclusive page access, except for
+ * a locked page table
+ *
+ * - a page cache insertion, a swapin fault, or a migration
+ * have the page locked
+ */
pc->mem_cgroup = memcg;
- SetPageCgroupUsed(pc);
+ pc->flags = PCG_USED | PCG_MEM | PCG_MEMSW;
if (lrucare) {
if (was_on_lru) {
spin_unlock_irq(&zone->lru_lock);
}
- mem_cgroup_charge_statistics(memcg, page, anon, nr_pages);
- unlock_page_cgroup(pc);
-
+ mem_cgroup_charge_statistics(memcg, page, nr_pages);
/*
* "charge_statistics" updated event counter. Then, check it.
* Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-#define PCGF_NOCOPY_AT_SPLIT (1 << PCG_LOCK | 1 << PCG_MIGRATION)
/*
* Because tail pages are not marked as "used", set it. We're under
* zone->lru_lock, 'splitting on pmd' and compound_lock.
for (i = 1; i < HPAGE_PMD_NR; i++) {
pc = head_pc + i;
pc->mem_cgroup = memcg;
- pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
+ pc->flags = head_pc->flags;
}
__this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS_HUGE],
HPAGE_PMD_NR);
{
unsigned long flags;
int ret;
- bool anon = PageAnon(page);
VM_BUG_ON(from == to);
VM_BUG_ON_PAGE(PageLRU(page), page);
if (nr_pages > 1 && !PageTransHuge(page))
goto out;
- lock_page_cgroup(pc);
-
ret = -EINVAL;
if (!PageCgroupUsed(pc) || pc->mem_cgroup != from)
- goto unlock;
+ goto out;
move_lock_mem_cgroup(from, &flags);
- if (!anon && page_mapped(page)) {
+ if (!PageAnon(page) && page_mapped(page)) {
__this_cpu_sub(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED],
nr_pages);
__this_cpu_add(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED],
nr_pages);
}
- mem_cgroup_charge_statistics(from, page, anon, -nr_pages);
+ mem_cgroup_charge_statistics(from, page, -nr_pages);
+
+ /*
+ * It is safe to change pc->mem_cgroup here because the page
+ * is referenced, charged, and isolated - we can't race with
+ * uncharging, charging, migration, or LRU putback.
+ */
/* caller should have done css_get */
pc->mem_cgroup = to;
- mem_cgroup_charge_statistics(to, page, anon, nr_pages);
+ mem_cgroup_charge_statistics(to, page, nr_pages);
move_unlock_mem_cgroup(from, &flags);
ret = 0;
-unlock:
- unlock_page_cgroup(pc);
/*
* check events
*/
return ret;
}
-static void mem_cgroup_do_uncharge(struct mem_cgroup *memcg,
- unsigned int nr_pages,
- const enum charge_type ctype)
-{
- struct memcg_batch_info *batch = NULL;
- bool uncharge_memsw = true;
-
- /* If swapout, usage of swap doesn't decrease */
- if (!do_swap_account || ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
- uncharge_memsw = false;
-
- batch = ¤t->memcg_batch;
- /*
- * In usual, we do css_get() when we remember memcg pointer.
- * But in this case, we keep res->usage until end of a series of
- * uncharges. Then, it's ok to ignore memcg's refcnt.
- */
- if (!batch->memcg)
- batch->memcg = memcg;
- /*
- * do_batch > 0 when unmapping pages or inode invalidate/truncate.
- * In those cases, all pages freed continuously can be expected to be in
- * the same cgroup and we have chance to coalesce uncharges.
- * But we do uncharge one by one if this is killed by OOM(TIF_MEMDIE)
- * because we want to do uncharge as soon as possible.
- */
-
- if (!batch->do_batch || test_thread_flag(TIF_MEMDIE))
- goto direct_uncharge;
-
- if (nr_pages > 1)
- goto direct_uncharge;
-
- /*
- * In typical case, batch->memcg == mem. This means we can
- * merge a series of uncharges to an uncharge of res_counter.
- * If not, we uncharge res_counter ony by one.
- */
- if (batch->memcg != memcg)
- goto direct_uncharge;
- /* remember freed charge and uncharge it later */
- batch->nr_pages++;
- if (uncharge_memsw)
- batch->memsw_nr_pages++;
- return;
-direct_uncharge:
- res_counter_uncharge(&memcg->res, nr_pages * PAGE_SIZE);
- if (uncharge_memsw)
- res_counter_uncharge(&memcg->memsw, nr_pages * PAGE_SIZE);
- if (unlikely(batch->memcg != memcg))
- memcg_oom_recover(memcg);
-}
-
-/*
- * uncharge if !page_mapped(page)
- */
-static struct mem_cgroup *
-__mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype,
- bool end_migration)
-{
- struct mem_cgroup *memcg = NULL;
- unsigned int nr_pages = 1;
- struct page_cgroup *pc;
- bool anon;
-
- if (mem_cgroup_disabled())
- return NULL;
-
- if (PageTransHuge(page)) {
- nr_pages <<= compound_order(page);
- VM_BUG_ON_PAGE(!PageTransHuge(page), page);
- }
- /*
- * Check if our page_cgroup is valid
- */
- pc = lookup_page_cgroup(page);
- if (unlikely(!PageCgroupUsed(pc)))
- return NULL;
-
- lock_page_cgroup(pc);
-
- memcg = pc->mem_cgroup;
-
- if (!PageCgroupUsed(pc))
- goto unlock_out;
-
- anon = PageAnon(page);
-
- switch (ctype) {
- case MEM_CGROUP_CHARGE_TYPE_ANON:
- /*
- * Generally PageAnon tells if it's the anon statistics to be
- * updated; but sometimes e.g. mem_cgroup_uncharge_page() is
- * used before page reached the stage of being marked PageAnon.
- */
- anon = true;
- /* fallthrough */
- case MEM_CGROUP_CHARGE_TYPE_DROP:
- /* See mem_cgroup_prepare_migration() */
- if (page_mapped(page))
- goto unlock_out;
- /*
- * Pages under migration may not be uncharged. But
- * end_migration() /must/ be the one uncharging the
- * unused post-migration page and so it has to call
- * here with the migration bit still set. See the
- * res_counter handling below.
- */
- if (!end_migration && PageCgroupMigration(pc))
- goto unlock_out;
- break;
- case MEM_CGROUP_CHARGE_TYPE_SWAPOUT:
- if (!PageAnon(page)) { /* Shared memory */
- if (page->mapping && !page_is_file_cache(page))
- goto unlock_out;
- } else if (page_mapped(page)) /* Anon */
- goto unlock_out;
- break;
- default:
- break;
- }
-
- mem_cgroup_charge_statistics(memcg, page, anon, -nr_pages);
-
- ClearPageCgroupUsed(pc);
- /*
- * pc->mem_cgroup is not cleared here. It will be accessed when it's
- * freed from LRU. This is safe because uncharged page is expected not
- * to be reused (freed soon). Exception is SwapCache, it's handled by
- * special functions.
- */
-
- unlock_page_cgroup(pc);
- /*
- * even after unlock, we have memcg->res.usage here and this memcg
- * will never be freed, so it's safe to call css_get().
- */
- memcg_check_events(memcg, page);
- if (do_swap_account && ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) {
- mem_cgroup_swap_statistics(memcg, true);
- css_get(&memcg->css);
- }
- /*
- * Migration does not charge the res_counter for the
- * replacement page, so leave it alone when phasing out the
- * page that is unused after the migration.
- */
- if (!end_migration)
- mem_cgroup_do_uncharge(memcg, nr_pages, ctype);
-
- return memcg;
-
-unlock_out:
- unlock_page_cgroup(pc);
- return NULL;
-}
-
-void mem_cgroup_uncharge_page(struct page *page)
-{
- /* early check. */
- if (page_mapped(page))
- return;
- VM_BUG_ON_PAGE(page->mapping && !PageAnon(page), page);
- /*
- * If the page is in swap cache, uncharge should be deferred
- * to the swap path, which also properly accounts swap usage
- * and handles memcg lifetime.
- *
- * Note that this check is not stable and reclaim may add the
- * page to swap cache at any time after this. However, if the
- * page is not in swap cache by the time page->mapcount hits
- * 0, there won't be any page table references to the swap
- * slot, and reclaim will free it and not actually write the
- * page to disk.
- */
- if (PageSwapCache(page))
- return;
- __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_ANON, false);
-}
-
-void mem_cgroup_uncharge_cache_page(struct page *page)
-{
- VM_BUG_ON_PAGE(page_mapped(page), page);
- VM_BUG_ON_PAGE(page->mapping, page);
- __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE, false);
-}
-
/*
* Batch_start/batch_end is called in unmap_page_range/invlidate/trucate.
* In that cases, pages are freed continuously and we can expect pages
batch->memcg = NULL;
}
-#ifdef CONFIG_SWAP
-/*
- * called after __delete_from_swap_cache() and drop "page" account.
- * memcg information is recorded to swap_cgroup of "ent"
- */
-void
-mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent, bool swapout)
-{
- struct mem_cgroup *memcg;
- int ctype = MEM_CGROUP_CHARGE_TYPE_SWAPOUT;
-
- if (!swapout) /* this was a swap cache but the swap is unused ! */
- ctype = MEM_CGROUP_CHARGE_TYPE_DROP;
-
- memcg = __mem_cgroup_uncharge_common(page, ctype, false);
-
- /*
- * record memcg information, if swapout && memcg != NULL,
- * css_get() was called in uncharge().
- */
- if (do_swap_account && swapout && memcg)
- swap_cgroup_record(ent, mem_cgroup_id(memcg));
-}
-#endif
-
#ifdef CONFIG_MEMCG_SWAP
-/*
- * called from swap_entry_free(). remove record in swap_cgroup and
- * uncharge "memsw" account.
- */
-void mem_cgroup_uncharge_swap(swp_entry_t ent)
+static void mem_cgroup_swap_statistics(struct mem_cgroup *memcg,
+ bool charge)
{
- struct mem_cgroup *memcg;
- unsigned short id;
-
- if (!do_swap_account)
- return;
-
- id = swap_cgroup_record(ent, 0);
- rcu_read_lock();
- memcg = mem_cgroup_lookup(id);
- if (memcg) {
- /*
- * We uncharge this because swap is freed. This memcg can
- * be obsolete one. We avoid calling css_tryget_online().
- */
- res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
- mem_cgroup_swap_statistics(memcg, false);
- css_put(&memcg->css);
- }
- rcu_read_unlock();
+ int val = (charge) ? 1 : -1;
+ this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_SWAP], val);
}
/**
}
#endif
-/*
- * Before starting migration, account PAGE_SIZE to mem_cgroup that the old
- * page belongs to.
- */
-void mem_cgroup_prepare_migration(struct page *page, struct page *newpage,
- struct mem_cgroup **memcgp)
-{
- struct mem_cgroup *memcg = NULL;
- unsigned int nr_pages = 1;
- struct page_cgroup *pc;
-
- *memcgp = NULL;
-
- if (mem_cgroup_disabled())
- return;
-
- if (PageTransHuge(page))
- nr_pages <<= compound_order(page);
-
- pc = lookup_page_cgroup(page);
- lock_page_cgroup(pc);
- if (PageCgroupUsed(pc)) {
- memcg = pc->mem_cgroup;
- css_get(&memcg->css);
- /*
- * At migrating an anonymous page, its mapcount goes down
- * to 0 and uncharge() will be called. But, even if it's fully
- * unmapped, migration may fail and this page has to be
- * charged again. We set MIGRATION flag here and delay uncharge
- * until end_migration() is called
- *
- * Corner Case Thinking
- * A)
- * When the old page was mapped as Anon and it's unmap-and-freed
- * while migration was ongoing.
- * If unmap finds the old page, uncharge() of it will be delayed
- * until end_migration(). If unmap finds a new page, it's
- * uncharged when it make mapcount to be 1->0. If unmap code
- * finds swap_migration_entry, the new page will not be mapped
- * and end_migration() will find it(mapcount==0).
- *
- * B)
- * When the old page was mapped but migraion fails, the kernel
- * remaps it. A charge for it is kept by MIGRATION flag even
- * if mapcount goes down to 0. We can do remap successfully
- * without charging it again.
- *
- * C)
- * The "old" page is under lock_page() until the end of
- * migration, so, the old page itself will not be swapped-out.
- * If the new page is swapped out before end_migraton, our
- * hook to usual swap-out path will catch the event.
- */
- if (PageAnon(page))
- SetPageCgroupMigration(pc);
- }
- unlock_page_cgroup(pc);
- /*
- * If the page is not charged at this point,
- * we return here.
- */
- if (!memcg)
- return;
-
- *memcgp = memcg;
- /*
- * We charge new page before it's used/mapped. So, even if unlock_page()
- * is called before end_migration, we can catch all events on this new
- * page. In the case new page is migrated but not remapped, new page's
- * mapcount will be finally 0 and we call uncharge in end_migration().
- */
- /*
- * The page is committed to the memcg, but it's not actually
- * charged to the res_counter since we plan on replacing the
- * old one and only one page is going to be left afterwards.
- */
- commit_charge(newpage, memcg, nr_pages, PageAnon(page), false);
-}
-
-/* remove redundant charge if migration failed*/
-void mem_cgroup_end_migration(struct mem_cgroup *memcg,
- struct page *oldpage, struct page *newpage, bool migration_ok)
-{
- struct page *used, *unused;
- struct page_cgroup *pc;
- bool anon;
-
- if (!memcg)
- return;
-
- if (!migration_ok) {
- used = oldpage;
- unused = newpage;
- } else {
- used = newpage;
- unused = oldpage;
- }
- anon = PageAnon(used);
- __mem_cgroup_uncharge_common(unused,
- anon ? MEM_CGROUP_CHARGE_TYPE_ANON
- : MEM_CGROUP_CHARGE_TYPE_CACHE,
- true);
- css_put(&memcg->css);
- /*
- * We disallowed uncharge of pages under migration because mapcount
- * of the page goes down to zero, temporarly.
- * Clear the flag and check the page should be charged.
- */
- pc = lookup_page_cgroup(oldpage);
- lock_page_cgroup(pc);
- ClearPageCgroupMigration(pc);
- unlock_page_cgroup(pc);
-
- /*
- * If a page is a file cache, radix-tree replacement is very atomic
- * and we can skip this check. When it was an Anon page, its mapcount
- * goes down to 0. But because we added MIGRATION flage, it's not
- * uncharged yet. There are several case but page->mapcount check
- * and USED bit check in mem_cgroup_uncharge_page() will do enough
- * check. (see prepare_charge() also)
- */
- if (anon)
- mem_cgroup_uncharge_page(used);
-}
-
-/*
- * At replace page cache, newpage is not under any memcg but it's on
- * LRU. So, this function doesn't touch res_counter but handles LRU
- * in correct way. Both pages are locked so we cannot race with uncharge.
- */
-void mem_cgroup_replace_page_cache(struct page *oldpage,
- struct page *newpage)
-{
- struct mem_cgroup *memcg = NULL;
- struct page_cgroup *pc;
-
- if (mem_cgroup_disabled())
- return;
-
- pc = lookup_page_cgroup(oldpage);
- /* fix accounting on old pages */
- lock_page_cgroup(pc);
- if (PageCgroupUsed(pc)) {
- memcg = pc->mem_cgroup;
- mem_cgroup_charge_statistics(memcg, oldpage, false, -1);
- ClearPageCgroupUsed(pc);
- }
- unlock_page_cgroup(pc);
-
- /*
- * When called from shmem_replace_page(), in some cases the
- * oldpage has already been charged, and in some cases not.
- */
- if (!memcg)
- return;
- /*
- * Even if newpage->mapping was NULL before starting replacement,
- * the newpage may be on LRU(or pagevec for LRU) already. We lock
- * LRU while we overwrite pc->mem_cgroup.
- */
- commit_charge(newpage, memcg, 1, false, true);
-}
-
#ifdef CONFIG_DEBUG_VM
static struct page_cgroup *lookup_page_cgroup_used(struct page *page)
{
if (page) {
pc = lookup_page_cgroup(page);
/*
- * Do only loose check w/o page_cgroup lock.
- * mem_cgroup_move_account() checks the pc is valid or not under
- * the lock.
+ * Do only loose check w/o serialization.
+ * mem_cgroup_move_account() checks the pc is valid or
+ * not under LRU exclusion.
*/
if (PageCgroupUsed(pc) && pc->mem_cgroup == mc.from) {
ret = MC_TARGET_PAGE;
}
#endif
+#ifdef CONFIG_MEMCG_SWAP
+/**
+ * mem_cgroup_swapout - transfer a memsw charge to swap
+ * @page: page whose memsw charge to transfer
+ * @entry: swap entry to move the charge to
+ *
+ * Transfer the memsw charge of @page to @entry.
+ */
+void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
+{
+ struct page_cgroup *pc;
+ unsigned short oldid;
+
+ VM_BUG_ON_PAGE(PageLRU(page), page);
+ VM_BUG_ON_PAGE(page_count(page), page);
+
+ if (!do_swap_account)
+ return;
+
+ pc = lookup_page_cgroup(page);
+
+ /* Readahead page, never charged */
+ if (!PageCgroupUsed(pc))
+ return;
+
+ VM_BUG_ON_PAGE(!(pc->flags & PCG_MEMSW), page);
+
+ oldid = swap_cgroup_record(entry, mem_cgroup_id(pc->mem_cgroup));
+ VM_BUG_ON_PAGE(oldid, page);
+
+ pc->flags &= ~PCG_MEMSW;
+ css_get(&pc->mem_cgroup->css);
+ mem_cgroup_swap_statistics(pc->mem_cgroup, true);
+}
+
+/**
+ * mem_cgroup_uncharge_swap - uncharge a swap entry
+ * @entry: swap entry to uncharge
+ *
+ * Drop the memsw charge associated with @entry.
+ */
+void mem_cgroup_uncharge_swap(swp_entry_t entry)
+{
+ struct mem_cgroup *memcg;
+ unsigned short id;
+
+ if (!do_swap_account)
+ return;
+
+ id = swap_cgroup_record(entry, 0);
+ rcu_read_lock();
+ memcg = mem_cgroup_lookup(id);
+ if (memcg) {
+ res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
+ mem_cgroup_swap_statistics(memcg, false);
+ css_put(&memcg->css);
+ }
+ rcu_read_unlock();
+}
+#endif
+
/**
* mem_cgroup_try_charge - try charging a page
* @page: page to charge
VM_BUG_ON_PAGE(!PageTransHuge(page), page);
}
- commit_charge(page, memcg, nr_pages, PageAnon(page), lrucare);
+ commit_charge(page, memcg, nr_pages, lrucare);
if (do_swap_account && PageSwapCache(page)) {
swp_entry_t entry = { .val = page_private(page) };
cancel_charge(memcg, nr_pages);
}
+/**
+ * mem_cgroup_uncharge - uncharge a page
+ * @page: page to uncharge
+ *
+ * Uncharge a page previously charged with mem_cgroup_try_charge() and
+ * mem_cgroup_commit_charge().
+ */
+void mem_cgroup_uncharge(struct page *page)
+{
+ struct memcg_batch_info *batch;
+ unsigned int nr_pages = 1;
+ struct mem_cgroup *memcg;
+ struct page_cgroup *pc;
+ unsigned long flags;
+
+ VM_BUG_ON_PAGE(PageLRU(page), page);
+ VM_BUG_ON_PAGE(page_count(page), page);
+
+ if (mem_cgroup_disabled())
+ return;
+
+ pc = lookup_page_cgroup(page);
+
+ /* Every final put_page() ends up here */
+ if (!PageCgroupUsed(pc))
+ return;
+
+ if (PageTransHuge(page)) {
+ nr_pages <<= compound_order(page);
+ VM_BUG_ON_PAGE(!PageTransHuge(page), page);
+ }
+ /*
+ * Nobody should be changing or seriously looking at
+ * pc->mem_cgroup and pc->flags at this point, we have fully
+ * exclusive access to the page.
+ */
+ memcg = pc->mem_cgroup;
+ flags = pc->flags;
+ pc->flags = 0;
+
+ mem_cgroup_charge_statistics(memcg, page, -nr_pages);
+ memcg_check_events(memcg, page);
+
+ batch = ¤t->memcg_batch;
+ if (!batch->memcg)
+ batch->memcg = memcg;
+ else if (batch->memcg != memcg)
+ goto uncharge;
+ if (nr_pages > 1)
+ goto uncharge;
+ if (!batch->do_batch)
+ goto uncharge;
+ if (test_thread_flag(TIF_MEMDIE))
+ goto uncharge;
+ if (flags & PCG_MEM)
+ batch->nr_pages++;
+ if (flags & PCG_MEMSW)
+ batch->memsw_nr_pages++;
+ return;
+uncharge:
+ if (flags & PCG_MEM)
+ res_counter_uncharge(&memcg->res, nr_pages * PAGE_SIZE);
+ if (flags & PCG_MEMSW)
+ res_counter_uncharge(&memcg->memsw, nr_pages * PAGE_SIZE);
+ if (batch->memcg != memcg)
+ memcg_oom_recover(memcg);
+}
+
+/**
+ * mem_cgroup_migrate - migrate a charge to another page
+ * @oldpage: currently charged page
+ * @newpage: page to transfer the charge to
+ * @lrucare: page might be on LRU already
+ *
+ * Migrate the charge from @oldpage to @newpage.
+ *
+ * Both pages must be locked, @newpage->mapping must be set up.
+ */
+void mem_cgroup_migrate(struct page *oldpage, struct page *newpage,
+ bool lrucare)
+{
+ unsigned int nr_pages = 1;
+ struct page_cgroup *pc;
+
+ VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
+ VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
+ VM_BUG_ON_PAGE(PageLRU(oldpage), oldpage);
+ VM_BUG_ON_PAGE(PageLRU(newpage), newpage);
+ VM_BUG_ON_PAGE(PageAnon(oldpage) != PageAnon(newpage), newpage);
+
+ if (mem_cgroup_disabled())
+ return;
+
+ pc = lookup_page_cgroup(oldpage);
+ if (!PageCgroupUsed(pc))
+ return;
+
+ VM_BUG_ON_PAGE(!(pc->flags & PCG_MEM), oldpage);
+ VM_BUG_ON_PAGE(!(pc->flags & PCG_MEMSW), oldpage);
+ pc->flags &= ~(PCG_MEM | PCG_MEMSW);
+
+ if (PageTransHuge(oldpage)) {
+ nr_pages <<= compound_order(oldpage);
+ VM_BUG_ON_PAGE(!PageTransHuge(oldpage), oldpage);
+ VM_BUG_ON_PAGE(!PageTransHuge(newpage), newpage);
+ }
+
+ commit_charge(newpage, pc->mem_cgroup, nr_pages, lrucare);
+}
+
/*
* subsys_initcall() for memory controller.
*
projects / karo-tx-linux.git / commitdiff