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Date:   Tue, 11 Dec 2018 23:18:23 -0800
From:   Christoph Hellwig <hch@infradead.org>
To:     Chuck Lever <chuck.lever@oracle.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        linux-rdma@vger.kernel.org,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH v3 03/24] xprtrdma: Remove support for FMR memory
 registration
Message-ID: <20181212071823.GA23247@infradead.org>
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On Tue, Dec 11, 2018 at 10:29:10AM -0500, Chuck Lever wrote:
> 
> 
> > On Dec 11, 2018, at 9:02 AM, Christoph Hellwig <hch@infradead.org> wrote:
> > 
> > Can we also kill off rpcrdma_memreg_ops now?  Indirect calls are
> > suprisingly expensive, especially in our post-spectre world, and
> > xprtrdma always seemed a little odd with this supper generic
> > abstraction.
> 
> Yep, I'm considering replacing those indirect calls.
> 
> However, note that the RPC layer is full of them too, as is the
> DMA operations that are used by xprtrdma. I'm not sure it will make
> much of a difference.

I've posted a series to remove them for the DMA fast path, and every
indirect calls adds additional cost.