lkml.org 
[lkml]   [2015]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 3/3] context_tracking,x86: remove extraneous irq disable & enable from context tracking on syscall entry
On 05/07/2015 08:29 AM, Ingo Molnar wrote:
>
> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
>
>>>> We cannot take the lock_trace(task) from irq context, and we
>>>> probably do not need to anyway, since we do not care about a
>>>> precise stack trace for the task.
>>>
>>> So one worry with this and similar approaches of statistically
>>> detecting user mode would be the fact that on the way out to
>>> user-space we don't really destroy the previous call trace - we
>>> just pop off the stack (non-destructively), restore RIPs and are
>>> gone.
>>>
>>> We'll need that percpu flag I suspect.
>>
>> Note we have the context tracking state which tells where the
>> current task is: user/system/guest.
>
> Yes, but that overhead is what I'm suggesting we get rid of, I thought
> Rik was trying to find a mechanism that would be independent of that?

One thing at a time :)

I am working on the timer sampling stuff, which should be easy
to adapt to a different user/system/guest/irq/softirq/... tracking
thing, if somebody else comes up with a more efficient way to do
that.

--
All rights reversed


\
 
 \ /
  Last update: 2015-05-07 18:01    [W:0.090 / U:7.696 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site