Re: Scheduler fairness problem on 2.6 series

["Prakash K. Cheemplavam" <prakashkc@gmx.de>]

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Con Kolivas wrote:
| Prakash K. Cheemplavam wrote:
|
|> 124910    9.8170  vmlinux                  tcp_poll
|> 123356    9.6949  vmlinux                  sys_select
|> 85634     6.7302  vmlinux                  do_select
|> 71858     5.6475  vmlinux                  sysenter_past_esp
|> 62093     4.8801  vmlinux                  kfree
|> 51658     4.0600  vmlinux                  __copy_to_user_ll
|> 37495     2.9468  vmlinux                  max_select_fd
|> 36949     2.9039  vmlinux                  __kmalloc
|> 22700     1.7841  vmlinux                  __copy_from_user_ll
|> 14587     1.1464  vmlinux                  do_gettimeofday
|>
| It looks like your select timeouts are too short and when the cpu load
| goes up they repeatedly timeout wasting cpu cycles.
| I quote from `man select_tut` under the section SELECT LAW:
|
| 1. You should always try use select without a timeout. Your program
|  should have nothing to do if there is no  data  available.  Code
|  that  depends  on timeouts is not usually portable and difficult
|  to debug.
|

Thanks for your explanation. I cannot do anything about it, as it is
mpich related. So I'll ask them if they could change its behaviour a bit
so that it eats less CPU on a single CPU machine.

Cheers,

Prakash
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