Messages in this thread | | | Date | Sat, 08 Jun 2013 10:18:50 +0800 | From | Alex Shi <> | Subject | Re: [RFC patch 1/4] sched: change cfs_rq load avg to unsigned long |
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On 06/07/2013 05:07 PM, Vincent Guittot wrote: > On 7 June 2013 09:29, Alex Shi <alex.shi@intel.com> wrote: >> > Since the 'u64 runnable_load_avg, blocked_load_avg' in cfs_rq struct are >> > smaller than 'unsigned long' cfs_rq->load.weight. We don't need u64 >> > vaiables to describe them. unsigned long is more efficient and convenience. >> > > Hi Alex, > > I just want to point out that we can't have more than 48388 tasks with > highest priority on a runqueue with an unsigned long on a 32 bits > system. I don't know if we can reach such kind of limit on a 32bits > machine ? For sure, not on an embedded system.
Thanks question! It should be a talked problem. I just remember the conclusion is when you get the up bound task number, you already run out the memory space on 32 bit.
Just for kernel resource for a process, it need 2 pages stack. mm_struct, task_struct, task_stats, vm_area_struct, page table etc. these are already beyond 4 pages. so 4 * 4k * 48388 = 774MB. plus user level resources.
So, usually the limited task number in Linux is often far lower this number: $ulimit -u.
Anyway, at least, the runnable_load_avg is smaller then load.weight. if load.weight can use long type, runablle_load_avg is no reason can't.
-- Thanks Alex
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