[lkml]   [2009]   [Jun]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC patch] Use IPI_shortcut for lapic timer broadcast
On Mon, Jun 29, 2009 at 3:20 PM, Ingo Molnar<> wrote:
> * Luming Yu <> wrote:
>> Hello,
>> We need to use IPI shortcut to send lapic timer broadcast
>> to avoid the latency of sending IPI one bye one on systems with many
>> logical processors when NO_HZ is disabled.
>> Without this patch,I have seen upstream kernel with RHEL 5 kernel
>> config boot hang .
> hm, that might be a valid optimization - but why does the lack of
> this optimization result in a hang?

It is hang caused by kernel code for work around lapic-timer-stop issue.
With HZ=1000, and a lot of cpus (eg. 64 logical cpus), cpu 0 will be
busy working on send TIMER IPI instead of making progress in boot
(right after deep-C-state has been used).

>        Ingo
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2009-06-29 10:07    [W:0.068 / U:3.936 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site