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Date: Sun, 28 Feb 2016 02:26:14 -0800 From: "santosh.shilimkar@...cle.com" <santosh.shilimkar@...cle.com> To: Christoph Hellwig <hch@...radead.org> Cc: netdev@...r.kernel.org, davem@...emloft.net, linux-kernel@...r.kernel.org Subject: Re: [net-next][PATCH v2 11/13] RDS: IB: add Fastreg MR (FRMR) detection support On 2/28/16 1:08 AM, Christoph Hellwig wrote: > On Sat, Feb 27, 2016 at 06:19:48PM -0800, Santosh Shilimkar wrote: >> Discovere Fast Memmory Registration support using IB device >> IB_DEVICE_MEM_MGT_EXTENSIONS. Certain HCA might support just FRMR >> or FMR or both FMR and FRWR. In case both mr type are supported, >> default FMR is used. >> >> Default MR is still kept as FMR against what everyone else >> is following. Default will be changed to FRMR once the >> RDS performance with FRMR is comparable with FMR. The >> work is in progress for the same. >> >> Signed-off-by: Santosh Shilimkar <ssantosh@...nel.org> >> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@...cle.com> >> --- >> v2: Dropped the module parameter as suggested by David Miller > > This means we only use the safer method if the HCA doesn't support > the other one. All other RDMA ULP that support both methods have > a module_param so the veto from Dave is a bit unfortunate. Anyway, > let's get the code in for now and figure out what to use later. > Indeed. It wasn't really deal breaker for RDS so I agreed to drop it. > Just curious: where / how do you see worse peformance using FRs? > I wouldn't call it worse but its not comparable. Use case is multi-threaded RDS RDMA perf test(s). Hopefully the follow up series which am working on should minimise the gap. I am leaving the details for later, but one of the main issue I saw was contention on driver post_send() lock from send, MR reg and MR invalidation. Regards, Santosh
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