lkml.org 
[lkml]   [2018]   [Jun]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] IB/mad: Use IDR instead of per-port list
On Thu, Jun 07, 2018 at 04:26:46PM -0600, Jason Gunthorpe wrote:
> On Thu, Jun 07, 2018 at 12:08:32PM -0700, Matthew Wilcox wrote:
> >
> > Hans reports a bug where the mlx4 driver uses the MSB of the agent number
> > to store slave number, meaning we can only use agent numbers up to 2^24.
> > Fix this by using an IDR to assign the agent numbers and also look up the
> > agent when a MSD packet is received.
> >
> > I've changed the locking substantially, so this may well have a
> > performance issue. There are a few different possibilities for fixing
> > that, including moving to an RCU-based lookup.
>
> I do like this better than the last series..
>
> This are is somewhat performance sensitive and it would be nice to
> avoid this global lock.

OK, I wasn't sure whether it was worth it.

> What about using a read/write spinlock instead of the IDR internal
> lock? Then all the per-port reading threads calling find_mad_agent can
> run concurrently..

It'd be better to switch to RCU ... the IDR is RCU-safe, but the
version/class/method or OUI match isn't. Do you have any feeling on
the relative frequency of the two types of "routing"?

Actually, I think we can use the radix tree data structure for the
version/class/method too ... that's going to take a little more work.

\
 
 \ /
  Last update: 2018-06-08 01:49    [W:0.066 / U:0.076 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site