On Fri, Jun 7, 2013 at 7:18 PM, Alex Shi <[email protected]> wrote: > On 06/07/2013 05:07 PM, Vincent Guittot wrote: >> On 7 June 2013 09:29, Alex Shi <[email protected]> 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.
This should be ok. Note that: runnable_load_avg = \Sum se->load_avg_contrib <= \Sum se->load.weight = cfs_rq->load.weight And load_weight uses unsigned longs also. blocked_load_avg must be also safe since anything appearing in blocked load could have appeared in runnable load and we've said that was ok above. Reviewed-By: Paul Turner <[email protected]> > > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
