On 6/8/2016 1:53 PM, Chuck Lever wrote:
On Jun 8, 2016, at 1:40 PM, Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote:
On Wed, Jun 08, 2016 at 03:06:56PM +0000, Trond Myklebust wrote:
That would be a mount parameter which would only apply to RDMA since
everything else uses dynamic slot allocation these days. Iād prefer to
avoid that.
The only reason RDMA cannot allocate MRs on the fly is
performance.. Maybe a dynamic scheme is the right answer..
Dynamically managing the MR free list should be straightforward:
1. Allocate a minimum number of MRs at transport creation time
2. If workload causes the transport to exhaust its supply of
MRs, kick a worker thread to create some more
3. Maybe add a shrinker that can trim the MR list when the
system is under memory pressure
SMB Direct in Windows Server 2012R2 does this, and it works
extremely well. We reduced MR demand by approximately a factor
of 50, since it's rare that many connections are active at
high queue depths.
Tom.
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