Date: Sat, 13 Sep 2014 16:28:20 -0400 (EDT) From: Rick Macklem <rmacklem@uoguelph.ca> To: Hans Petter Selasky <hps@selasky.org> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Adrian Chadd <adrian@freebsd.org> Subject: Re: svn commit: r271504 - in head/sys: dev/oce dev/vmware/vmxnet3 dev/xen/netfront net netinet ofed/drivers/net/mlx4 Message-ID: <1971026585.35877589.1410640100903.JavaMail.root@uoguelph.ca> In-Reply-To: <5414A5A7.9030108@selasky.org>
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Hans Petter Selasky wrote: > On 09/13/14 22:04, Rick Macklem wrote: > > Hans Petter Selasky wrote: > >> On 09/13/14 18:54, Adrian Chadd wrote: > >>> Hi, > >>> > >>> Just for the record: > >>> > >>> * I'm glad you're tackling the TSO config stuff; > >>> * I'm not glad you're trying to pack it into a u_int rather than > >>> creating a new structure and adding fields for it. > >>> > >>> I appreciate that you're trying to rush this in before 10.1, but > >>> this > >>> is exactly why things shouldn't be rushed in before release > >>> deadlines. > >>> :) > >>> > >>> I'd really like to see this be broken out as a structure and the > >>> bit > >>> shifting games for what really shouldn't be packed into a u_int > >>> fixed. > >>> Otherwise this is going to be deadweight that has to persist past > >>> 11.0. > >>> > >> > >> Hi Adrian, > >> > >> I can make that change for -current, making the new structure and > >> such. > >> This change was intended for 10 where there is only one u_int for > >> this > >> information. Or do you want me to change that in 10 too? > >> > > Well, there are spare fields (if_ispare[4]) in struct ifnet that I > > believe can be used for new u_ints when MFC'ng a patch that adds > > fields to struct ifnet in head. (If I have this wrong, someone > > please > > correct me.) > > > > I'll admit I don't really see an advantage to defining a structure > > vs > > just defining a couple of additional u_ints, but so long as the > > structure > > doesn't cause alignment issues for any arch, I don't see a problem > > with > > a structure. > > > > I tend to agree with Adrian that this shouldn't be rushed. (I, > > personally, > > think that if_hw_tsomax was poorly chosen, but that is already in > > use, so > > I think we need to add to that and not replace it.) > > > > I also hope that your testing has included quite a bit of activity > > on > > an NFS mount using TSO and the default 64K rsize, wsize, since that > > is > > going to generate a bunch of 35 mbuf transmit fragment lists and > > there > > is an edge case where the total data length excluding ethernet > > header > > is just under 64K (by less than the ethernet header length) where > > the > > list must be split by tcp_output() to avoid disaster. > > Hi, > > The ethernet and VLAN headers are still subtracted. > Where? I couldn't see it when I glanced at the patch. (hdrlen in tcp_output() does not include ethernet header length and that is the only thing I see subtracted from the max_len.) I see the default set to (65536 - 4). I don't know why you subtracted 4 but I would have expected the max ethernet header length to be subtracted here? Note that this must be subtracted before use by tcp_output() because there are several network device drivers that support 32 transmit segments and this means that the TSO segment including ethernet headers must fit in 65536bytes (32 * MCLBYTES). If it does not, then NFS over these devices is busted because even m_defrag() can`t make them fit. rick rick > --HPS > > >
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