linux-kernel - RE: [[PATCH v1] 12/37] [CIFS] SMBD: Handle send completion from CQ

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Date:   Mon, 14 Aug 2017 18:16:28 +0000
From:   Long Li <longli@...rosoft.com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     Steve French <sfrench@...ba.org>,
        "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
        "samba-technical@...ts.samba.org" <samba-technical@...ts.samba.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [[PATCH v1] 12/37] [CIFS] SMBD: Handle send completion from CQ



> -----Original Message-----
> From: Christoph Hellwig [mailto:hch@...radead.org]
> Sent: Sunday, August 13, 2017 3:20 AM
> To: Long Li <longli@...rosoft.com>
> Cc: Steve French <sfrench@...ba.org>; linux-cifs@...r.kernel.org; samba-
> technical@...ts.samba.org; linux-kernel@...r.kernel.org; Long Li
> <longli@...rosoft.com>
> Subject: Re: [[PATCH v1] 12/37] [CIFS] SMBD: Handle send completion from
> CQ
> 
> You seem to be doing memory allocations and frees for every packet on the
> write.  At least for other RDMA protocols that would have been a major
> performance issue.

The size of SGE array passed to IB is unknown, so I don't know how much to pre-allocate in advance. But it seems this size is not big when passed down from CIFS. I will look at pre-allocating buffer if this is an issue.

> 
> Do you have any performance numbers and/or profiles of the code?

I will look into profiling.