Re: [RFC][PATCH 0/3] impelemnt cgroup_(subsys)_disabled in generic.

[Glauber Costa <glommer@parallels.com>]

On 11/23/2011 06:28 AM, KAMEZAWA Hiroyuki wrote:
>
> Now, memory cgroup has 'mem_cgroup_disabled()' in memcontrol.h
>
> I made a brief trial to use static_branch() for that function. At doing that,
> I thought it will be better to implement generic cgroup functions rather
> than having memory cgroup's its own one.
>
> This series consists of 3 patches
> 1 .... implement cgroup_xxxx_disabled() in generic.
> 2 .... use jump_label for cgroup_xxxx_disabled()
> 3 .... remove mem_cgroup_disabled() in memcontrol.c
>
> And I post this series for getting review/comments.
> I'm not sure patches for using jump_label is worth to be merged.
>
> I did a test to run a loop
> 	while(-) {
> 		mmap(1M)
> 		touch all pages
> 		munmap()
> 	}
>
> and measured performance score in ROOT cgroup. Here,
>
> (Before patch)
>     182,932,842,128 cycles                    #    0.000 GHz                     [33.33%]
>     192,711,643,877 instructions              #    1.05  insns per cycle         [49.99%]
>         761,483,416 cache-references                                             [49.98%]
>             159,908 cache-misses              #    0.021 % of all cache refs     [50.00%]
>      33,253,084,874 branches                                                     [33.34%]
>         109,796,792 branch-misses             #    0.33% of all branches         [33.34%]
>
>        58.289265709 seconds time elapsed
>
> (After patch)
>   Performance counter stats for './malloc 1':
>
>     183,068,407,487 cycles                    #    0.000 GHz                     [33.33%]
>     191,834,248,678 instructions              #    1.05  insns per cycle         [50.00%]
>         798,635,028 cache-references                                             [49.98%]
>              95,562 cache-misses              #    0.012 % of all cache refs     [50.00%]
>      32,755,318,286 branches                                                     [33.34%]
>          77,774,624 branch-misses             #    0.24% of all branches         [33.34%]
>
>        58.332356996 seconds time elapsed
>
> There is no differece in 'time' ;)
> But I got an impression that 'branch' score gets better in several tests.
>

branch and cache misses are a lot smaller as well. I think this is a win.