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From: Jason Gunthorpe <jgg@mellanox.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: hans.westgaard.ry@oracle.com,
	"Doug Ledford" <dledford@redhat.com>,
	linux-rdma@vger.kernel.org,
	"Håkon Bugge" <haakon.bugge@oracle.com>,
	"Parav Pandit" <parav@mellanox.com>,
	"Jack Morgenstein" <jackm@dev.mellanox.co.il>,
	"Pravin Shedge" <pravin.shedge4linux@gmail.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC] IB/mad: Use IDR instead of per-port list
Date: Thu, 7 Jun 2018 16:26:46 -0600	[thread overview]
Message-ID: <20180607222646.GX14597@mellanox.com> (raw)
In-Reply-To: <20180607190832.GA24370@bombadil.infradead.org>

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.

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..

Thanks,
Jason

  reply	other threads:[~2018-06-07 22:27 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-07 19:08 Matthew Wilcox
2018-06-07 22:26 ` Jason Gunthorpe [this message]
2018-06-07 23:49   ` Matthew Wilcox
2018-06-08  2:11     ` Jason Gunthorpe

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