lkml.org 
[lkml]   [2013]   [Nov]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] kmod: Run usermodehelpers only on cpus allowed for kthreadd V2
On Fri, Nov 08, 2013 at 05:05:35PM +0000, Christoph Lameter wrote:
> On Fri, 8 Nov 2013, Frederic Weisbecker wrote:
>
> > But it looks like it always end up calling a workqueue. May be I missed something though.
> >
> > Now we can argue that this workqueue seem to create kernel threads, which in turn create other kernel thread (uhh?)
> > and I don't know if those inherit the kworker affinity. But from a quick look, it seems to me that
> > this is what we want.
>
> Right. The problem is that the affinity cannot be inherited since
> usermodehelper may be called from a workqueue or other restricted kernel
> context. The main point of the usermodehelper logic is to work itself out
> of the restrictions of the context in which is was called to be able to
> fork off a kernel thread that then can call a userspace helper program.

I understand, but why not solving that from the workqueue affinity? We want to
solve the issue of unbound workqueues in CPU isolation anyway.

>
> I want to restrict on which processors this working out of the limiting
> context can occur. It should not occur on low latency processors nor
> should user space stuff be run there.
>
> Without this patch we see various processes being sprinkled over all the
> processors in the system when usermodehelper is invoked.

I got that, and I too am interested in solving this problem. I'm not fighting
against the purpose of this patch but against the way we solve that.


\
 
 \ /
  Last update: 2013-11-08 20:41    [W:0.255 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site