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Subject[UPDATED][PATCH][mmotm] Help Root Memory Cgroup Resource Counters Scale Better (v5)
* nishimura@mxp.nes.nec.co.jp <nishimura@mxp.nes.nec.co.jp> [2009-08-13 16:26:40]:

> > @@ -1855,9 +1883,14 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
> > break;
> > }
> >
> > - res_counter_uncharge(&mem->res, PAGE_SIZE, &soft_limit_excess);
> > - if (do_swap_account && (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT))
> > - res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
> > + if (!mem_cgroup_is_root(mem)) {
> > + res_counter_uncharge(&mem->res, PAGE_SIZE, &soft_limit_excess);
> > + if (do_swap_account &&
> > + (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT))
> > + res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
> > + }
> > + if (ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT && mem_cgroup_is_root(mem))
> > + mem_cgroup_swap_statistics(mem, true);
> Hmm, if we don't count MEM_CGROUP_STAT_SWAPOUT properly about other groups than the root,
> memsw.usage_in_bytes of the root would be incorrect in use_hierarchy==1 case, right?
>


OK, does this look better


From: Balbir Singh <balbir@linux.vnet.ibm.com>

Enhancement: Remove the overhead of root based resource counter accounting

This patch reduces the resource counter overhead (mostly spinlock)
associated with the root cgroup. This is a part of the several
patches to reduce mem cgroup overhead. I had posted other
approaches earlier (including using percpu counters). Those
patches will be a natural addition and will be added iteratively
on top of these.

The patch stops resource counter accounting for the root cgroup.
The data for display is derived from the statisitcs we maintain
via mem_cgroup_charge_statistics (which is more scalable).
What happens today is that, we do double accounting, once using
res_counter_charge() and once using memory_cgroup_charge_statistics().
For the root, since we don't implement limits any more, we don't
need to track every charge via res_counter_charge() and check
for limit being exceeded and reclaim.

The main mem->res usage_in_bytes can be derived by summing
the cache and rss usage data from memory statistics
(MEM_CGROUP_STAT_RSS and MEM_CGROUP_STAT_CACHE). However, for
memsw->res usage_in_bytes, we need additional data about
swapped out memory. This patch adds a MEM_CGROUP_STAT_SWAPOUT
and uses that along with MEM_CGROUP_STAT_RSS and MEM_CGROUP_STAT_CACHE
to derive the memsw data. This data is computed recursively
when hierarchy is enabled.

The tests results I see on a 24 way show that

1. The lock contention disappears from /proc/lock_stats
2. The results of the test are comparable to running with
cgroup_disable=memory.

Here is a sample of my program runs

Without Patch

Performance counter stats for '/home/balbir/parallel_pagefault':

7192804.124144 task-clock-msecs # 23.937 CPUs
424691 context-switches # 0.000 M/sec
267 CPU-migrations # 0.000 M/sec
28498113 page-faults # 0.004 M/sec
5826093739340 cycles # 809.989 M/sec
408883496292 instructions # 0.070 IPC
7057079452 cache-references # 0.981 M/sec
3036086243 cache-misses # 0.422 M/sec

300.485365680 seconds time elapsed

With cgroup_disable=memory

Performance counter stats for '/home/balbir/parallel_pagefault':

7182183.546587 task-clock-msecs # 23.915 CPUs
425458 context-switches # 0.000 M/sec
203 CPU-migrations # 0.000 M/sec
92545093 page-faults # 0.013 M/sec
6034363609986 cycles # 840.185 M/sec
437204346785 instructions # 0.072 IPC
6636073192 cache-references # 0.924 M/sec
2358117732 cache-misses # 0.328 M/sec

300.320905827 seconds time elapsed

With this patch applied

Performance counter stats for '/home/balbir/parallel_pagefault':

7191619.223977 task-clock-msecs # 23.955 CPUs
422579 context-switches # 0.000 M/sec
88 CPU-migrations # 0.000 M/sec
91946060 page-faults # 0.013 M/sec
5957054385619 cycles # 828.333 M/sec
1058117350365 instructions # 0.178 IPC
9161776218 cache-references # 1.274 M/sec
1920494280 cache-misses # 0.267 M/sec

300.218764862 seconds time elapsed


Data from Prarit (kernel compile with make -j64 on a 64
CPU/32G machine)

For a single run

Without patch

real 27m8.988s
user 87m24.916s
sys 382m6.037s

With patch

real 4m18.607s
user 84m58.943s
sys 50m52.682s


With config turned off

real 4m54.972s
user 90m13.456s
sys 50m19.711s

NOTE: The data looks counterintuitive due to the increased performance
with the patch, even over the config being turned off. We probably need
more runs, but so far all testing has shown that the patches definitely
help.


Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
---
mm/memcontrol.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++---------
1 files changed, 99 insertions(+), 20 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 48a38e1..36a8b6d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -70,6 +70,7 @@ enum mem_cgroup_stat_index {
MEM_CGROUP_STAT_PGPGIN_COUNT, /* # of pages paged in */
MEM_CGROUP_STAT_PGPGOUT_COUNT, /* # of pages paged out */
MEM_CGROUP_STAT_EVENTS, /* sum of pagein + pageout for internal use */
+ MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */

MEM_CGROUP_STAT_NSTATS,
};
@@ -478,6 +479,19 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
return mz;
}

+static void mem_cgroup_swap_statistics(struct mem_cgroup *mem,
+ bool charge)
+{
+ int val = (charge) ? 1 : -1;
+ struct mem_cgroup_stat *stat = &mem->stat;
+ struct mem_cgroup_stat_cpu *cpustat;
+ int cpu = get_cpu();
+
+ cpustat = &stat->cpustat[cpu];
+ __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_SWAPOUT, val);
+ put_cpu();
+}
+
static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
struct page_cgroup *pc,
bool charge)
@@ -1281,9 +1295,11 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
VM_BUG_ON(css_is_removed(&mem->css));

while (1) {
- int ret;
+ int ret = 0;
unsigned long flags = 0;

+ if (mem_cgroup_is_root(mem))
+ goto done;
ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res,
&soft_fail_res);
if (likely(!ret)) {
@@ -1343,6 +1359,7 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
if (mem_cgroup_soft_limit_check(mem_over_soft_limit))
mem_cgroup_update_tree(mem_over_soft_limit, page);
}
+done:
return 0;
nomem:
css_put(&mem->css);
@@ -1415,9 +1432,12 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
lock_page_cgroup(pc);
if (unlikely(PageCgroupUsed(pc))) {
unlock_page_cgroup(pc);
- res_counter_uncharge(&mem->res, PAGE_SIZE, NULL);
- if (do_swap_account)
- res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
+ if (!mem_cgroup_is_root(mem)) {
+ res_counter_uncharge(&mem->res, PAGE_SIZE, NULL);
+ if (do_swap_account)
+ res_counter_uncharge(&mem->memsw, PAGE_SIZE,
+ NULL);
+ }
css_put(&mem->css);
return;
}
@@ -1494,7 +1514,8 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
if (pc->mem_cgroup != from)
goto out;

- res_counter_uncharge(&from->res, PAGE_SIZE, NULL);
+ if (!mem_cgroup_is_root(from))
+ res_counter_uncharge(&from->res, PAGE_SIZE, NULL);
mem_cgroup_charge_statistics(from, pc, false);

page = pc->page;
@@ -1513,7 +1534,7 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
1);
}

- if (do_swap_account)
+ if (do_swap_account && !mem_cgroup_is_root(from))
res_counter_uncharge(&from->memsw, PAGE_SIZE, NULL);
css_put(&from->css);

@@ -1584,9 +1605,11 @@ uncharge:
/* drop extra refcnt by try_charge() */
css_put(&parent->css);
/* uncharge if move fails */
- res_counter_uncharge(&parent->res, PAGE_SIZE, NULL);
- if (do_swap_account)
- res_counter_uncharge(&parent->memsw, PAGE_SIZE, NULL);
+ if (!mem_cgroup_is_root(parent)) {
+ res_counter_uncharge(&parent->res, PAGE_SIZE, NULL);
+ if (do_swap_account)
+ res_counter_uncharge(&parent->memsw, PAGE_SIZE, NULL);
+ }
return ret;
}

@@ -1775,7 +1798,10 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
* This recorded memcg can be obsolete one. So, avoid
* calling css_tryget
*/
- res_counter_uncharge(&memcg->memsw, PAGE_SIZE, NULL);
+ if (!mem_cgroup_is_root(memcg))
+ res_counter_uncharge(&memcg->memsw, PAGE_SIZE,
+ NULL);
+ mem_cgroup_swap_statistics(memcg, false);
mem_cgroup_put(memcg);
}
rcu_read_unlock();
@@ -1800,9 +1826,11 @@ void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem)
return;
if (!mem)
return;
- res_counter_uncharge(&mem->res, PAGE_SIZE, NULL);
- if (do_swap_account)
- res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
+ if (!mem_cgroup_is_root(mem)) {
+ res_counter_uncharge(&mem->res, PAGE_SIZE, NULL);
+ if (do_swap_account)
+ res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
+ }
css_put(&mem->css);
}

@@ -1855,9 +1883,14 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
break;
}

- res_counter_uncharge(&mem->res, PAGE_SIZE, &soft_limit_excess);
- if (do_swap_account && (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT))
- res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
+ if (!mem_cgroup_is_root(mem)) {
+ res_counter_uncharge(&mem->res, PAGE_SIZE, &soft_limit_excess);
+ if (do_swap_account &&
+ (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT))
+ res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
+ }
+ if (ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
+ mem_cgroup_swap_statistics(mem, true);
mem_cgroup_charge_statistics(mem, pc, false);

ClearPageCgroupUsed(pc);
@@ -1948,7 +1981,9 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent)
* We uncharge this because swap is freed.
* This memcg can be obsolete one. We avoid calling css_tryget
*/
- res_counter_uncharge(&memcg->memsw, PAGE_SIZE, NULL);
+ if (!mem_cgroup_is_root(memcg))
+ res_counter_uncharge(&memcg->memsw, PAGE_SIZE, NULL);
+ mem_cgroup_swap_statistics(memcg, false);
mem_cgroup_put(memcg);
}
rcu_read_unlock();
@@ -2451,20 +2486,64 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
return retval;
}

+struct mem_cgroup_idx_data {
+ s64 val;
+ enum mem_cgroup_stat_index idx;
+};
+
+static int
+mem_cgroup_get_idx_stat(struct mem_cgroup *mem, void *data)
+{
+ struct mem_cgroup_idx_data *d = data;
+ d->val += mem_cgroup_read_stat(&mem->stat, d->idx);
+ return 0;
+}
+
+static void
+mem_cgroup_get_recursive_idx_stat(struct mem_cgroup *mem,
+ enum mem_cgroup_stat_index idx, s64 *val)
+{
+ struct mem_cgroup_idx_data d;
+ d.idx = idx;
+ d.val = 0;
+ mem_cgroup_walk_tree(mem, &d, mem_cgroup_get_idx_stat);
+ *val = d.val;
+}
+
static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
{
struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
- u64 val = 0;
+ u64 idx_val, val;
int type, name;

type = MEMFILE_TYPE(cft->private);
name = MEMFILE_ATTR(cft->private);
switch (type) {
case _MEM:
- val = res_counter_read_u64(&mem->res, name);
+ if (name == RES_USAGE && mem_cgroup_is_root(mem)) {
+ mem_cgroup_get_recursive_idx_stat(mem,
+ MEM_CGROUP_STAT_CACHE, &idx_val);
+ val = idx_val;
+ mem_cgroup_get_recursive_idx_stat(mem,
+ MEM_CGROUP_STAT_RSS, &idx_val);
+ val += idx_val;
+ val <<= PAGE_SHIFT;
+ } else
+ val = res_counter_read_u64(&mem->res, name);
break;
case _MEMSWAP:
- val = res_counter_read_u64(&mem->memsw, name);
+ if (name == RES_USAGE && mem_cgroup_is_root(mem)) {
+ mem_cgroup_get_recursive_idx_stat(mem,
+ MEM_CGROUP_STAT_CACHE, &idx_val);
+ val = idx_val;
+ mem_cgroup_get_recursive_idx_stat(mem,
+ MEM_CGROUP_STAT_RSS, &idx_val);
+ val += idx_val;
+ mem_cgroup_get_recursive_idx_stat(mem,
+ MEM_CGROUP_STAT_SWAPOUT, &idx_val);
+ val <<= PAGE_SHIFT;
+ } else
+ val = res_counter_read_u64(&mem->memsw, name);
break;
default:
BUG();
--
Balbir


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