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

[Long Li]

> -----Original Message-----
> From: Tom Talpey
> Sent: Monday, August 14, 2017 12:29 PM
> To: Christoph Hellwig <hch@xxxxxxxxxxxxx>; Long Li <longli@xxxxxxxxxxxxx>
> Cc: Steve French <sfrench@xxxxxxxxx>; linux-cifs@xxxxxxxxxxxxxxx; samba-
> technical@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: RE: [[PATCH v1] 04/37] [CIFS] SMBD: Define per-channel SMBD
> transport parameters and default values
> 
> > -----Original Message-----
> > From: linux-cifs-owner@xxxxxxxxxxxxxxx [mailto:linux-cifs-
> > owner@xxxxxxxxxxxxxxx] On Behalf Of Christoph Hellwig
> > Sent: Sunday, August 13, 2017 6:12 AM
> > To: Long Li <longli@xxxxxxxxxxxxx>
> > Cc: Steve French <sfrench@xxxxxxxxx>; linux-cifs@xxxxxxxxxxxxxxx;
> > samba- technical@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Long
> > Li <longli@xxxxxxxxxxxxx>
> > 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.