--Paul Jackson <[EMAIL PROTECTED]> wrote (on Sunday, October 03, 2004 09:02:09 -0700):
> Martin wrote: >> The way cpusets uses the current cpus_allowed mechanism is, to me, the most >> worrying thing about it. Frankly, the cpus_allowed thing is kind of tacked >> onto the existing scheduler, and not at all integrated into it, and doesn't >> work well if you use it heavily (eg bind all the processes to a few CPUs, >> and watch the rest of the system kill itself). > > True. One detail of what you say I'm unclear on -- how will the rest of > the system kill itself? Why wouldn't the unemployed CPUs just idle > around, waiting for something to do? I think last time I looked they just sat there saying: Rebalance! Ooooh, CPU 3 over there looks heavily loaded, I'll steal something. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. Humpf. I give up. Rebalance! Ooooh, CPU 3 over there looks heavily loaded, I'll steal something. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. Humpf. I give up. Rebalance! Ooooh, CPU 3 over there looks heavily loaded, I'll steal something. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. That one. Try to migrate. Oops, no cpus_allowed bars me. Humpf. I give up. ... ad infinitum. Desperately boring, and rather ineffective. > As I recall, Ingo added task->cpus_allowed for the Tux in-kernel web > server a few years back, and I piggy backed the cpuset stuff on that, to > keep my patch size small. > > Likely your same concerns apply to the task->mems_allowed field that > I added, in the same fashion, in my cpuset patch of recent. Mmm, I'm less concerned about that one, or at least I can't specifically see how it breaks. > We need a mechanism that the cpuset apparatus respects that maps each > CPU to a sched_domain, exactly one sched_domain for any given CPU at any > point in time, regardless of which task it is considering running at the > moment. Somewhat like dual-channeled disks, having more than one > sched_domain apply at the same time to a given CPU leads to confusions > best avoided unless desparately needed. Agreed. The cpus_allowed mechanism doesn't seem well suited to heavy use anyway (I think John Hawkes had problems with it too). That's not your fault ... but I'm not convinced it's a good foundation to be building further things on either ;-) M. ------------------------------------------------------- This SF.net email is sponsored by: IT Product Guide on ITManagersJournal Use IT products in your business? Tell us what you think of them. Give us Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more http://productguide.itmanagersjournal.com/guidepromo.tmpl _______________________________________________ ckrm-tech mailing list https://lists.sourceforge.net/lists/listinfo/ckrm-tech
