linux-kernel - RE: [[PATCH v1] 04/37] [CIFS] SMBD: Define per-channel SMBD transport parameters and default values

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Message-ID: <CY4PR21MB0182F9ED2FC8791190F4C947CE8C0@CY4PR21MB0182.namprd21.prod.outlook.com>
Date:   Mon, 14 Aug 2017 22:57:22 +0000
From:   Long Li <longli@...rosoft.com>
To:     Tom Talpey <ttalpey@...rosoft.com>,
        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] 04/37] [CIFS] SMBD: Define per-channel SMBD transport
 parameters and default values



> -----Original Message-----
> From: Tom Talpey
> Sent: Monday, August 14, 2017 12:29 PM
> To: Christoph Hellwig <hch@...radead.org>; 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
> Subject: RE: [[PATCH v1] 04/37] [CIFS] SMBD: Define per-channel SMBD
> transport parameters and default values
> 
> > -----Original Message-----
> > From: linux-cifs-owner@...r.kernel.org [mailto:linux-cifs-
> > owner@...r.kernel.org] On Behalf Of Christoph Hellwig
> > Sent: Sunday, August 13, 2017 6:12 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] 04/37] [CIFS] SMBD: Define per-channel SMBD
> > transport parameters and default values
> >
> > > +/*
> > > + * Per RDMA transport connection parameters
> > > + * as defined in [MS-SMBD] 3.1.1.1
> > > + */
> > > +static int receive_credit_max = 512; static int send_credit_target
> > > += 512; static int max_send_size = 8192; static int
> > > +max_fragmented_recv_size = 1024*1024; static int max_receive_size =
> > > +8192;
> >
> > Are these protocol constants?  If so please use either #defines or
> > enums with upper case names for them.
> 
> These are not defined constants, but the values beg for some explanatory
> text why they are chosen. Windows uses, and negotiates by default, a 1364-
> byte maximum send size, and caps credits to 255. The other values match.
> 
> BTW, the parameters are defined in MS-SMBD 3.1.1.1 but the chosen values
> are in behavior notes 2 and 7.

I will change those values to more inline with what Windows choses. The different values don't have a visible impact to performance while RDMA read/write is used.

> 
> Tom.