lkml.org 
[lkml]   [2011]   [Mar]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Add support for multiple MSI on x86
On Fri, 4 Mar 2011, Micha Nelissen wrote:
> Jesse Barnes wrote:
> > On Sun, 13 Feb 2011 21:25:21 +0100
> > Micha Nelissen <micha@neli.hopto.org> wrote:
> >
> > > Patch is based on earlier patch from Matthew Wilcox.
> >
> > I like this before when Matthew was working on it too
>
> If I understood Thomas' concerns well, it sounds like this feature is
> inherently incompatible with big SMP systems. Therefore it has no chance of
> ever being accepted into mainline in whatever form?

First of all MSI is replaced by MSI-X which does not have the
shortcomings of MSI vs. the vector allocation.

Though if we can come up with a scheme which does not create nested
loops over possibly hundreds of CPUs with interrupts disabled and
global locks held, I have no objections.

One possible solution would be to reserve a block of vectors on all
cpus at boot time via a command line option for MSI block
allocations. That would simply use a bitmap protected by a mutex to
lookup a free vector space. That would avoid the whole loop issue and
work for most of the systems which need to deal with such MSI multi
vector devices. Warning: Just an idea :)

Thanks,

tglx


\
 
 \ /
  Last update: 2011-03-08 22:09    [W:0.581 / U:0.120 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site