Date: Fri, 5 Sep 2014 19:21:15 -0400 (EDT) From: Rick Macklem <rmacklem@uoguelph.ca> To: Hans Petter Selasky <hps@selasky.org> Cc: freebsd-net@freebsd.org, Eric Joyner <ricera10@gmail.com>, FreeBSD Current <freebsd-current@freebsd.org>, Scott Long <scottl@freebsd.org>, Jack F Vogel <jfvogel@gmail.com> Subject: Re: [RFC] Patch to improve TSO limitation formula in general Message-ID: <1527367342.33029385.1409959275542.JavaMail.root@uoguelph.ca> In-Reply-To: <540A3C91.406@selasky.org>
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Hans Petter Selasky wrote: > On 09/06/14 00:09, Rick Macklem wrote: > > Hans Petter Selesky wrote: > >> On 09/05/14 23:19, Eric Joyner wrote: > >>> There are some concerns if we use this with devices that ixl > >>> supports: > >>> > >>> - The maximum fragment size is 16KB-1, which isn't a power of 2. > >>> > >> > >> Hi Eric, > >> > >> Multiplying by powers of two are more fast, than non-powers of > >> two. > >> So > >> in this case you would have to use 8KB as a maximum. > >> > > Well, I'm no architecture expert, but I really doubt the CPU delay > > of a > > non-power of 2 multiply/divide is significant related to doing > > smaller > > TSO segments. Long ago (as in 1970s) I did work on machines where > > shifts > > for power of 2 multiply/divide was preferable, but these days I > > doubt it > > is going to matter?? > > > > Hi, > > You also need to patch LAGG and VLAN drivers? > Yep. I already ran into the fact that these drivers didn't pass if_hw_tsomax up and patched them for that recently. The same will be necessary for if_hw_tsomaxseg if/when it goes into head. As I said, this patch is currently completely untested and, even once I get it tested/working, there will need to be a discussion on freebsd-net@ w.r.t. whether it is appropriate for head. I will take a look at your patch around Monday. Btw, when setting if_hw_tsomax as I suggested in the first post, you will still end up doing a lot of m_defrag() calls for NFS RPC messages, but at least they will get through. rick > --HPS > > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to > "freebsd-net-unsubscribe@freebsd.org" >
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