Re: [PATCH -mmotm 3/4] memcg: dirty pages accounting and limitinginfrastructure
From: Daisuke Nishimura
Date: Mon Mar 08 2010 - 03:12:28 EST
On Mon, 8 Mar 2010 11:37:11 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> On Mon, 8 Mar 2010 11:17:24 +0900
> Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote:
>
> > > But IIRC, clear_writeback is done under treelock.... No ?
> > >
> > The place where NR_WRITEBACK is updated is out of tree_lock.
> >
> > 1311 int test_clear_page_writeback(struct page *page)
> > 1312 {
> > 1313 struct address_space *mapping = page_mapping(page);
> > 1314 int ret;
> > 1315
> > 1316 if (mapping) {
> > 1317 struct backing_dev_info *bdi = mapping->backing_dev_info;
> > 1318 unsigned long flags;
> > 1319
> > 1320 spin_lock_irqsave(&mapping->tree_lock, flags);
> > 1321 ret = TestClearPageWriteback(page);
> > 1322 if (ret) {
> > 1323 radix_tree_tag_clear(&mapping->page_tree,
> > 1324 page_index(page),
> > 1325 PAGECACHE_TAG_WRITEBACK);
> > 1326 if (bdi_cap_account_writeback(bdi)) {
> > 1327 __dec_bdi_stat(bdi, BDI_WRITEBACK);
> > 1328 __bdi_writeout_inc(bdi);
> > 1329 }
> > 1330 }
> > 1331 spin_unlock_irqrestore(&mapping->tree_lock, flags);
> > 1332 } else {
> > 1333 ret = TestClearPageWriteback(page);
> > 1334 }
> > 1335 if (ret)
> > 1336 dec_zone_page_state(page, NR_WRITEBACK);
> > 1337 return ret;
> > 1338 }
>
> We can move this up to under tree_lock. Considering memcg, all our target has "mapping".
>
> If we newly account bounce-buffers (for NILFS, FUSE, etc..), which has no ->mapping,
> we need much more complex new charge/uncharge theory.
>
> But yes, adding new lock scheme seems complicated. (Sorry Andrea.)
> My concerns is performance. We may need somehing new re-implementation of
> locks/migrate/charge/uncharge.
>
I agree. Performance is my concern too.
I made a patch below and measured the time(average of 10 times) of kernel build
on tmpfs(make -j8 on 8 CPU machine with 2.6.33 defconfig).
<before>
- root cgroup: 190.47 sec
- child cgroup: 192.81 sec
<after>
- root cgroup: 191.06 sec
- child cgroup: 193.06 sec
Hmm... about 0.3% slower for root, 0.1% slower for child.
===
From: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
In current implementation, we don't have to disable irq at lock_page_cgroup()
because the lock is never acquired in interrupt context.
But we are going to do it in later patch, so this patch encloses all of
lock_page_cgroup()/unlock_page_cgroup() with irq_disabled()/irq_enabled().
Signed-off-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 17 +++++++++++++++++
1 files changed, 17 insertions(+), 0 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 02ea959..e5ae1a1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1359,6 +1359,7 @@ void mem_cgroup_update_file_mapped(struct page *page, int val)
if (unlikely(!pc))
return;
+ local_irq_disable();
lock_page_cgroup(pc);
mem = pc->mem_cgroup;
if (!mem)
@@ -1374,6 +1375,7 @@ void mem_cgroup_update_file_mapped(struct page *page, int val)
done:
unlock_page_cgroup(pc);
+ local_irq_enable();
}
/*
@@ -1711,6 +1713,7 @@ struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
VM_BUG_ON(!PageLocked(page));
pc = lookup_page_cgroup(page);
+ local_irq_disable();
lock_page_cgroup(pc);
if (PageCgroupUsed(pc)) {
mem = pc->mem_cgroup;
@@ -1726,6 +1729,7 @@ struct mem_cgroup *try_get_mem_cgroup_from_page(struct page *page)
rcu_read_unlock();
}
unlock_page_cgroup(pc);
+ local_irq_enable();
return mem;
}
@@ -1742,9 +1746,11 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
if (!mem)
return;
+ local_irq_disable();
lock_page_cgroup(pc);
if (unlikely(PageCgroupUsed(pc))) {
unlock_page_cgroup(pc);
+ local_irq_enable();
mem_cgroup_cancel_charge(mem);
return;
}
@@ -1775,6 +1781,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
mem_cgroup_charge_statistics(mem, pc, true);
unlock_page_cgroup(pc);
+ local_irq_enable();
/*
* "charge_statistics" updated event counter. Then, check it.
* Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
@@ -1844,12 +1851,14 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
{
int ret = -EINVAL;
+ local_irq_disable();
lock_page_cgroup(pc);
if (PageCgroupUsed(pc) && pc->mem_cgroup == from) {
__mem_cgroup_move_account(pc, from, to, uncharge);
ret = 0;
}
unlock_page_cgroup(pc);
+ local_irq_enable();
/*
* check events
*/
@@ -1981,12 +1990,15 @@ int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
pc = lookup_page_cgroup(page);
if (!pc)
return 0;
+ local_irq_disable();
lock_page_cgroup(pc);
if (PageCgroupUsed(pc)) {
unlock_page_cgroup(pc);
+ local_irq_enable();
return 0;
}
unlock_page_cgroup(pc);
+ local_irq_enable();
}
if (unlikely(!mm && !mem))
@@ -2182,6 +2194,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
if (unlikely(!pc || !PageCgroupUsed(pc)))
return NULL;
+ local_irq_disable();
lock_page_cgroup(pc);
mem = pc->mem_cgroup;
@@ -2222,6 +2235,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
mz = page_cgroup_zoneinfo(pc);
unlock_page_cgroup(pc);
+ local_irq_enable();
memcg_check_events(mem, page);
/* at swapout, this memcg will be accessed to record to swap */
@@ -2232,6 +2246,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
unlock_out:
unlock_page_cgroup(pc);
+ local_irq_enable();
return NULL;
}
@@ -2424,12 +2439,14 @@ int mem_cgroup_prepare_migration(struct page *page, struct mem_cgroup **ptr)
return 0;
pc = lookup_page_cgroup(page);
+ local_irq_disable();
lock_page_cgroup(pc);
if (PageCgroupUsed(pc)) {
mem = pc->mem_cgroup;
css_get(&mem->css);
}
unlock_page_cgroup(pc);
+ local_irq_enable();
if (mem) {
ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem, false);
--
1.6.4
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