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Message-Id: <20091109163420.5a2fa803.kamezawa.hiroyu@jp.fujitsu.com>
Date: Mon, 9 Nov 2009 16:34:20 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: balbir@...ux.vnet.ibm.com
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
cl@...ux-foundation.org,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/2] memcg make use of new percpu implementations
On Mon, 9 Nov 2009 12:34:21 +0530
Balbir Singh <balbir@...ux.vnet.ibm.com> wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> [2009-11-06 17:52:42]:
>
> > Hi,
> >
> > Recent updates on dynamic percpu allocation looks good and I tries to rewrite
> > memcg's poor implementation of percpu status counter.
> > (It's not NUMA-aware ...)
> > Thanks for great works.
> >
> > For this time. I added Christoph to CC because I'm not fully sure my usage of
> > __this_cpu_xxx is correct...I'm glad if you check the usage when you have time.
> >
> >
> > Patch 1/2 is just clean up (prepare for patch 2/2)
> > Patch 2/2 is for percpu.
> >
> > Tested on my 8cpu box and works well.
> > Pathcesa are against the latest mmotm.
>
> How do the test results look? DO you see a significant boost?
Because my test enviroment is just an SMP (not NUMA), improvement will
not be siginificant (visible), I think.
But It's good to make use of recent updates of per_cpu implementation. We
can make use of offset calculation methods of them and one-instruction-access
macros.
This is code size (PREEMPT=y)
[Before patch]
[kamezawa@...extal mmotm-2.6.32-Nov2]$ size mm/memcontrol.o
text data bss dec hex filename
22403 3420 4132 29955 7503 mm/memcontrol.o
[After patch]
[kamezawa@...extal mmotm-2.6.32-Nov2]$ size mm/memcontrol.o
text data bss dec hex filename
22188 3420 4132 29740 742c mm/memcontrol.o
Then, text size is surely reduced.
One example is mem_cgroup_swap_statistics(). This function is inlined
after this patch.
this code: mem_cgroup_uncharge_swap(), modifies percpu counter.
==
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
*/
if (!mem_cgroup_is_root(memcg))
res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
mem_cgroup_swap_statistics(memcg, false);
mem_cgroup_put(memcg);
}
==
[before patch]
mem_cgroup_swap_statistics() is not inlined and uses 0x69 bytes.
0000000000001d30 <mem_cgroup_swap_statistics>:
1d30: push %rbp
1d31: mov %rsp,%rbp
1d34: push %r12
<snip>
1d88: callq 1d8d <mem_cgroup_swap_statistics+0x5d>
1d8d: nopl (%rax)
1d90: jmp 1d83 <mem_cgroup_swap_statistics+0x53>
1d92: nopw %cs:0x0(%rax,%rax,1)
1d99:
[After patch]
mem_cgroup_uncharge_swap()'s inlined code.
3b67: cmp 0x0(%rip),%rax # 3b6e <mem_cgroup_uncharge_swap+0
xbe>
3b6e: je 3b81 <mem_cgroup_uncharge_swap+0xd1> <=== check mem_cgroup_is_root
3b70: lea 0x90(%rax),%rdi
3b77: mov $0x1000,%esi
3b7c: callq 3b81 <mem_cgroup_uncharge_swap+0xd1> <=== calling res_counter_uncahrge()
3b81: 48 89 df mov %rbx,%rdi
3b84: 48 8b 83 70 01 00 00 mov 0x170(%rbx),%rax <=== get offset of mem->cpustat
3b8b: 65 48 83 40 30 ff addq $0xffffffffffffffff,%gs:0x30(%rax) mem->cpustat.count[index]--;
3b91: e8 6a e0 ff ff callq 1c00 <mem_cgroup_put>
This uses 2 instruction.
Then, code size reduction is enough large, I think.
>BTW, I've been experimenting a bit with the earlier percpu counter patches,
> I might post an iteration once I have some good results.
>
Thank you, it's helpful.
Regards,
-Kame
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