cpu shielding.
Glauber Costa
glommer at parallels.com
Tue Feb 7 10:35:39 UTC 2012
On 02/07/2012 06:15 AM, Serge Hallyn wrote:
> Quoting atp (Andrew.Phillips at lmax.com):
>> Hello,
>>
>> Apologies if I'm about to ask a frequently asked question - I did
>> check back over the last couple of months.
>>
>> Is anyone working on cpu shielding for processes inside a cpu cgroup?
>>
>> We would like to run Java in containers, and unfortunately it likes to
>> know how many processors there are in the system - to initialise thread
>> pools and such like.
>>
>> I was thinking along these lines;
>>
>> --- fs/proc/stat.c.orig 2010-05-21 11:32:32.941258466 +0000
>> +++ fs/proc/stat.c 2010-05-21 11:40:47.681259133 +0000
>> @@ -39,7 +39,9 @@
>> getboottime(&boottime);
>> jif = boottime.tv_sec;
>>
>> - for_each_possible_cpu(i) {
>> +// for_each_possible_cpu(i) {
>> +// // refer to the visible cpus.
>> + for_each_cpu_and(i,cpu_possible_mask,(¤t->cpus_allowed)) {
>> user = cputime64_add(user, kstat_cpu(i).cpustat.user);
>> nice = cputime64_add(nice, kstat_cpu(i).cpustat.nice);
>> system = cputime64_add(system, kstat_cpu(i).cpustat.system);
>> @@ -78,7 +80,10 @@
>> (unsigned long long)cputime64_to_clock_t(steal),
>> (unsigned long long)cputime64_to_clock_t(guest),
>> (unsigned long long)cputime64_to_clock_t(guest_nice));
>> - for_each_online_cpu(i) {
>> +
>> +// for_each_online_cpu(i) {
>> +// // cgroup.
>> + for_each_cpu_and(i,cpu_online_mask,(¤t->cpus_allowed)) {
>>
>> /* Copy values here to work around gcc-2.95.3, gcc-2.96 */
>> user = kstat_cpu(i).cpustat.user;
>>
>> I'm sure that there are nicer ways of doing this, but Serge Hallyn
>> suggested a while ago that I post here. Even though it says 2010, the
>> patch above looks like it will go against 3.2.4 ok.
>>
>> Thanks,
>> Andy
>
> I'm afraid I haven't been following recent upstream discussions on
> this, but there are other people who want proc to show cgroup-limited
> information. See for instance http://lwn.net/Articles/460310/ . Glauber
> has also brought this up since then. I'd recommend pinging him.
>
> I'm all for /proc showing cgroup-filtered information, unconditionally.
>
Hi.
I have a patchset pending for review that deals with some part of that.
(http://lwn.net/Articles/479624/)
The way I see it, there are two parts of the problem: One of them is
keeping all those information consistently in the cgroup. I don't really
like your patch, btw, because it takes the process as the main entity,
and that is not really proc's idea. I'd go to the route of trying to
devise a cpumask from the cgroup, and then expose this. That said, I
believe anything in this area is far from a consensus.
Another problem is how to effectively display such data, after you
gathered it. I am not essentially opposed to unconditionally displaying
cgroup-filtered data as well, and I've sent a couple of patches trying
to achieve that. But there are some problems with this approach that are
preventing consensus now.
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