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SubjectRe: [patch 4/4] memcg: unify charge/uncharge quantities to units of pages
The update to 1/4 made one hunk of this one no longer apply, so to
save you the hassle, here is a complete replacement.

What I changed to visibly break new old-API users:

1. mem_cgroup_margin: sufficiently new to not have new users
developped that assume the return value to be in unit of bytes, so I
left it alone

2. __mem_cgroup_do_charge: dropped the underscores

3. __mem_cgroup_try_charge: moved @nr_pages parameter so that using
the old function signature would complain about passing integers for
pointers and vice versa

4. __mem_cgroup_commit_charge: same as 3.

5. mem_cgroup_move_account: same as 4.

6. __do_uncharge: renamed to mem_cgroup_do_uncharge

---
From: Johannes Weiner <hannes@cmpxchg.org>
Subject: [patch] memcg: unify charge/uncharge quantities to units of pages
There is no clear pattern when we pass a page count and when we pass a
byte count that is a multiple of PAGE_SIZE.

We never charge or uncharge subpage quantities, so convert it all to
page counts.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
mm/memcontrol.c | 135 ++++++++++++++++++++++++++----------------------------
1 files changed, 65 insertions(+), 70 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 63c65ab..78a79ea 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1092,16 +1092,16 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
* @mem: the memory cgroup
*
* Returns the maximum amount of memory @mem can be charged with, in
- * bytes.
+ * pages.
*/
-static unsigned long long mem_cgroup_margin(struct mem_cgroup *mem)
+static unsigned long mem_cgroup_margin(struct mem_cgroup *mem)
{
unsigned long long margin;

margin = res_counter_margin(&mem->res);
if (do_swap_account)
margin = min(margin, res_counter_margin(&mem->memsw));
- return margin;
+ return margin >> PAGE_SHIFT;
}

static unsigned int get_swappiness(struct mem_cgroup *memcg)
@@ -1637,7 +1637,7 @@ EXPORT_SYMBOL(mem_cgroup_update_page_stat);
* size of first charge trial. "32" comes from vmscan.c's magic value.
* TODO: maybe necessary to use big numbers in big irons.
*/
-#define CHARGE_SIZE (32 * PAGE_SIZE)
+#define CHARGE_BATCH 32U
struct memcg_stock_pcp {
struct mem_cgroup *cached; /* this never be root cgroup */
unsigned int nr_pages;
@@ -1812,9 +1812,10 @@ enum {
CHARGE_OOM_DIE, /* the current is killed because of OOM */
};

-static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
- int csize, bool oom_check)
+static int mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
+ unsigned int nr_pages, bool oom_check)
{
+ unsigned long csize = nr_pages * PAGE_SIZE;
struct mem_cgroup *mem_over_limit;
struct res_counter *fail_res;
unsigned long flags = 0;
@@ -1835,14 +1836,13 @@ static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
} else
mem_over_limit = mem_cgroup_from_res_counter(fail_res, res);
/*
- * csize can be either a huge page (HPAGE_SIZE), a batch of
- * regular pages (CHARGE_SIZE), or a single regular page
- * (PAGE_SIZE).
+ * nr_pages can be either a huge page (HPAGE_PMD_NR), a batch
+ * of regular pages (CHARGE_BATCH), or a single regular page (1).
*
* Never reclaim on behalf of optional batching, retry with a
* single page instead.
*/
- if (csize == CHARGE_SIZE)
+ if (nr_pages == CHARGE_BATCH)
return CHARGE_RETRY;

if (!(gfp_mask & __GFP_WAIT))
@@ -1850,7 +1850,7 @@ static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,

ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,
gfp_mask, flags);
- if (mem_cgroup_margin(mem_over_limit) >= csize)
+ if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
return CHARGE_RETRY;
/*
* Even though the limit is exceeded at this point, reclaim
@@ -1861,7 +1861,7 @@ static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
* unlikely to succeed so close to the limit, and we fall back
* to regular pages anyway in case of failure.
*/
- if (csize == PAGE_SIZE && ret)
+ if (nr_pages == 1 && ret)
return CHARGE_RETRY;

/*
@@ -1887,13 +1887,14 @@ static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
*/
static int __mem_cgroup_try_charge(struct mm_struct *mm,
gfp_t gfp_mask,
- struct mem_cgroup **memcg, bool oom,
- int page_size)
+ unsigned int nr_pages,
+ struct mem_cgroup **memcg,
+ bool oom)
{
+ unsigned int batch = max(CHARGE_BATCH, nr_pages);
int nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
struct mem_cgroup *mem = NULL;
int ret;
- int csize = max(CHARGE_SIZE, (unsigned long) page_size);

/*
* Unlike gloval-vm's OOM-kill, we're not in memory shortage
@@ -1918,7 +1919,7 @@ again:
VM_BUG_ON(css_is_removed(&mem->css));
if (mem_cgroup_is_root(mem))
goto done;
- if (page_size == PAGE_SIZE && consume_stock(mem))
+ if (nr_pages == 1 && consume_stock(mem))
goto done;
css_get(&mem->css);
} else {
@@ -1941,7 +1942,7 @@ again:
rcu_read_unlock();
goto done;
}
- if (page_size == PAGE_SIZE && consume_stock(mem)) {
+ if (nr_pages == 1 && consume_stock(mem)) {
/*
* It seems dagerous to access memcg without css_get().
* But considering how consume_stok works, it's not
@@ -1976,13 +1977,12 @@ again:
nr_oom_retries = MEM_CGROUP_RECLAIM_RETRIES;
}

- ret = __mem_cgroup_do_charge(mem, gfp_mask, csize, oom_check);
-
+ ret = mem_cgroup_do_charge(mem, gfp_mask, batch, oom_check);
switch (ret) {
case CHARGE_OK:
break;
case CHARGE_RETRY: /* not in OOM situation but retry */
- csize = page_size;
+ batch = nr_pages;
css_put(&mem->css);
mem = NULL;
goto again;
@@ -2003,8 +2003,8 @@ again:
}
} while (ret != CHARGE_OK);

- if (csize > page_size)
- refill_stock(mem, (csize - page_size) >> PAGE_SHIFT);
+ if (batch > nr_pages)
+ refill_stock(mem, batch - nr_pages);
css_put(&mem->css);
done:
*memcg = mem;
@@ -2083,12 +2083,10 @@ struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)

static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
struct page *page,
+ unsigned int nr_pages,
struct page_cgroup *pc,
- enum charge_type ctype,
- int page_size)
+ enum charge_type ctype)
{
- int nr_pages = page_size >> PAGE_SHIFT;
-
lock_page_cgroup(pc);
if (unlikely(PageCgroupUsed(pc))) {
unlock_page_cgroup(pc);
@@ -2177,26 +2175,28 @@ void mem_cgroup_split_huge_fixup(struct page *head, struct page *tail)
/**
* mem_cgroup_move_account - move account of the page
* @page: the page
+ * @nr_pages: number of regular pages (>1 for huge pages)
* @pc: page_cgroup of the page.
* @from: mem_cgroup which the page is moved from.
* @to: mem_cgroup which the page is moved to. @from != @to.
* @uncharge: whether we should call uncharge and css_put against @from.
- * @charge_size: number of bytes to charge (regular or huge page)
*
* The caller must confirm following.
* - page is not on LRU (isolate_page() is useful.)
- * - compound_lock is held when charge_size > PAGE_SIZE
+ * - compound_lock is held when nr_pages > 1
*
* This function doesn't do "charge" nor css_get to new cgroup. It should be
* done by a caller(__mem_cgroup_try_charge would be usefull). If @uncharge is
* true, this function does "uncharge" from old cgroup, but it doesn't if
* @uncharge is false, so a caller should do "uncharge".
*/
-static int mem_cgroup_move_account(struct page *page, struct page_cgroup *pc,
- struct mem_cgroup *from, struct mem_cgroup *to,
- bool uncharge, int charge_size)
+static int mem_cgroup_move_account(struct page *page,
+ unsigned int nr_pages,
+ struct page_cgroup *pc,
+ struct mem_cgroup *from,
+ struct mem_cgroup *to,
+ bool uncharge)
{
- int nr_pages = charge_size >> PAGE_SHIFT;
unsigned long flags;
int ret;

@@ -2209,7 +2209,7 @@ static int mem_cgroup_move_account(struct page *page, struct page_cgroup *pc,
* hold it.
*/
ret = -EBUSY;
- if (charge_size > PAGE_SIZE && !PageTransHuge(page))
+ if (nr_pages > 1 && !PageTransHuge(page))
goto out;

lock_page_cgroup(pc);
@@ -2267,7 +2267,7 @@ static int mem_cgroup_move_parent(struct page *page,
struct cgroup *cg = child->css.cgroup;
struct cgroup *pcg = cg->parent;
struct mem_cgroup *parent;
- int page_size = PAGE_SIZE;
+ unsigned int nr_pages;
unsigned long flags;
int ret;

@@ -2281,23 +2281,21 @@ static int mem_cgroup_move_parent(struct page *page,
if (isolate_lru_page(page))
goto put;

- if (PageTransHuge(page))
- page_size = HPAGE_SIZE;
+ nr_pages = hpage_nr_pages(page);

parent = mem_cgroup_from_cont(pcg);
- ret = __mem_cgroup_try_charge(NULL, gfp_mask,
- &parent, false, page_size);
+ ret = __mem_cgroup_try_charge(NULL, gfp_mask, nr_pages, &parent, false);
if (ret || !parent)
goto put_back;

- if (page_size > PAGE_SIZE)
+ if (nr_pages > 1)
flags = compound_lock_irqsave(page);

- ret = mem_cgroup_move_account(page, pc, child, parent, true, page_size);
+ ret = mem_cgroup_move_account(page, nr_pages, pc, child, parent, true);
if (ret)
- __mem_cgroup_cancel_charge(parent, page_size >> PAGE_SHIFT);
+ __mem_cgroup_cancel_charge(parent, nr_pages);

- if (page_size > PAGE_SIZE)
+ if (nr_pages > 1)
compound_unlock_irqrestore(page, flags);
put_back:
putback_lru_page(page);
@@ -2317,13 +2315,13 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
gfp_t gfp_mask, enum charge_type ctype)
{
struct mem_cgroup *mem = NULL;
- int page_size = PAGE_SIZE;
+ unsigned int nr_pages = 1;
struct page_cgroup *pc;
bool oom = true;
int ret;

if (PageTransHuge(page)) {
- page_size <<= compound_order(page);
+ nr_pages <<= compound_order(page);
VM_BUG_ON(!PageTransHuge(page));
/*
* Never OOM-kill a process for a huge page. The
@@ -2335,11 +2333,11 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
pc = lookup_page_cgroup(page);
BUG_ON(!pc); /* XXX: remove this and move pc lookup into commit */

- ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, oom, page_size);
+ ret = __mem_cgroup_try_charge(mm, gfp_mask, nr_pages, &mem, oom);
if (ret || !mem)
return ret;

- __mem_cgroup_commit_charge(mem, page, pc, ctype, page_size);
+ __mem_cgroup_commit_charge(mem, page, nr_pages, pc, ctype);
return 0;
}

@@ -2455,13 +2453,13 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
if (!mem)
goto charge_cur_mm;
*ptr = mem;
- ret = __mem_cgroup_try_charge(NULL, mask, ptr, true, PAGE_SIZE);
+ ret = __mem_cgroup_try_charge(NULL, mask, 1, ptr, true);
css_put(&mem->css);
return ret;
charge_cur_mm:
if (unlikely(!mm))
mm = &init_mm;
- return __mem_cgroup_try_charge(mm, mask, ptr, true, PAGE_SIZE);
+ return __mem_cgroup_try_charge(mm, mask, 1, ptr, true);
}

static void
@@ -2477,7 +2475,7 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
cgroup_exclude_rmdir(&ptr->css);
pc = lookup_page_cgroup(page);
mem_cgroup_lru_del_before_commit_swapcache(page);
- __mem_cgroup_commit_charge(ptr, page, pc, ctype, PAGE_SIZE);
+ __mem_cgroup_commit_charge(ptr, page, 1, pc, ctype);
mem_cgroup_lru_add_after_commit_swapcache(page);
/*
* Now swap is on-memory. This means this page may be
@@ -2529,12 +2527,13 @@ void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem)
__mem_cgroup_cancel_charge(mem, 1);
}

-static void
-__do_uncharge(struct mem_cgroup *mem, const enum charge_type ctype,
- int page_size)
+static void mem_cgroup_do_uncharge(struct mem_cgroup *mem,
+ 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;
@@ -2558,7 +2557,7 @@ __do_uncharge(struct mem_cgroup *mem, const enum charge_type ctype,
if (!batch->do_batch || test_thread_flag(TIF_MEMDIE))
goto direct_uncharge;

- if (page_size != PAGE_SIZE)
+ if (nr_pages > 1)
goto direct_uncharge;

/*
@@ -2574,9 +2573,9 @@ __do_uncharge(struct mem_cgroup *mem, const enum charge_type ctype,
batch->memsw_nr_pages++;
return;
direct_uncharge:
- res_counter_uncharge(&mem->res, page_size);
+ res_counter_uncharge(&mem->res, nr_pages * PAGE_SIZE);
if (uncharge_memsw)
- res_counter_uncharge(&mem->memsw, page_size);
+ res_counter_uncharge(&mem->memsw, nr_pages * PAGE_SIZE);
if (unlikely(batch->memcg != mem))
memcg_oom_recover(mem);
return;
@@ -2588,10 +2587,9 @@ direct_uncharge:
static struct mem_cgroup *
__mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
{
- int count;
- struct page_cgroup *pc;
struct mem_cgroup *mem = NULL;
- int page_size = PAGE_SIZE;
+ unsigned int nr_pages = 1;
+ struct page_cgroup *pc;

if (mem_cgroup_disabled())
return NULL;
@@ -2600,11 +2598,9 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
return NULL;

if (PageTransHuge(page)) {
- page_size <<= compound_order(page);
+ nr_pages <<= compound_order(page);
VM_BUG_ON(!PageTransHuge(page));
}
-
- count = page_size >> PAGE_SHIFT;
/*
* Check if our page_cgroup is valid
*/
@@ -2637,7 +2633,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
break;
}

- mem_cgroup_charge_statistics(mem, PageCgroupCache(pc), -count);
+ mem_cgroup_charge_statistics(mem, PageCgroupCache(pc), -nr_pages);

ClearPageCgroupUsed(pc);
/*
@@ -2658,7 +2654,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
mem_cgroup_get(mem);
}
if (!mem_cgroup_is_root(mem))
- __do_uncharge(mem, ctype, page_size);
+ mem_cgroup_do_uncharge(mem, nr_pages, ctype);

return mem;

@@ -2850,8 +2846,8 @@ static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
int mem_cgroup_prepare_migration(struct page *page,
struct page *newpage, struct mem_cgroup **ptr, gfp_t gfp_mask)
{
- struct page_cgroup *pc;
struct mem_cgroup *mem = NULL;
+ struct page_cgroup *pc;
enum charge_type ctype;
int ret = 0;

@@ -2907,7 +2903,7 @@ int mem_cgroup_prepare_migration(struct page *page,
return 0;

*ptr = mem;
- ret = __mem_cgroup_try_charge(NULL, gfp_mask, ptr, false, PAGE_SIZE);
+ ret = __mem_cgroup_try_charge(NULL, gfp_mask, 1, ptr, false);
css_put(&mem->css);/* drop extra refcnt */
if (ret || *ptr == NULL) {
if (PageAnon(page)) {
@@ -2934,7 +2930,7 @@ int mem_cgroup_prepare_migration(struct page *page,
ctype = MEM_CGROUP_CHARGE_TYPE_CACHE;
else
ctype = MEM_CGROUP_CHARGE_TYPE_SHMEM;
- __mem_cgroup_commit_charge(mem, page, pc, ctype, PAGE_SIZE);
+ __mem_cgroup_commit_charge(mem, page, 1, pc, ctype);
return ret;
}

@@ -4591,8 +4587,7 @@ one_by_one:
batch_count = PRECHARGE_COUNT_AT_ONCE;
cond_resched();
}
- ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem, false,
- PAGE_SIZE);
+ ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, 1, &mem, false);
if (ret || !mem)
/* mem_cgroup_clear_mc() will do uncharge later */
return -ENOMEM;
@@ -4937,8 +4932,8 @@ retry:
if (isolate_lru_page(page))
goto put;
pc = lookup_page_cgroup(page);
- if (!mem_cgroup_move_account(page, pc,
- mc.from, mc.to, false, PAGE_SIZE)) {
+ if (!mem_cgroup_move_account(page, 1, pc,
+ mc.from, mc.to, false)) {
mc.precharge--;
/* we uncharge from mc.from later. */
mc.moved_charge++;
--
1.7.4


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