On Thu, 24 Nov 2011 10:22:13 +0800
Li Zefan <lizf@xxxxxxxxxxxxxx> wrote:
> 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.
> >
> > Thanks,
> > -Kame
> >
> > P.S. maybe I can replace 'do_swap_account' with jump_label, too.
> >
>
> The numbers sugguest using jump label is a win.
>
> However I'm not quite convinced that we make it generic. The subsys.disabled flag
> was introduced long ago for memcg, but yet it has no other users.
>
We have generic cgroup_disable=xxxx boot options. But yes, it seems only memory cgroup
checks it in the hooks. (But I'm not sure it's not necessary to be checked..)
> So maybe for now make use of jump label in memcg only? We probably still needs
> a bit help from cgroup core, to provide a subsys->disable() callback.
>
Hm, ok. if this is not welcomed, I'll keep this only in memory cgroup and don't
touch cgroup.h.
Thank you for review.
Regards,
-Kame
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