Date: Sat, 4 May 2013 14:12:55 -0700 From: Jack Vogel <jfvogel@gmail.com> To: Andre Oppermann <andre@freebsd.org> Cc: FreeBSD Net <freebsd-net@freebsd.org>, Adrian Chadd <adrian@freebsd.org>, Richard Sharpe <realrichardsharpe@gmail.com> Subject: Re: Is there any way to limit the amount of data in an mbuf chain submitted to a driver? Message-ID: <CAFOYbck9PV0f5bqxe2xhOKY=0F8GNG=5m6SCzizH4J%2Bjs%2By1yw@mail.gmail.com> In-Reply-To: <518576EF.90706@freebsd.org> References: <CACyXjPwC5LRb7DT82n6PMbawceER3_nHko9c9tvrdQqceLiPww@mail.gmail.com> <CAJ-Vmon_5eyXMP5UOsVVBP8UgKQLw5HLMO1NgswoGb-zF=2wtg@mail.gmail.com> <CACyXjPzu3fXpo0i5YcdVBFye%2BRFTPUye=fgZ%2BycTkkiEmcRh%2BQ@mail.gmail.com> <CAFOYbcmZMW=-7Mwz9mwJLeM3Ju%2BF8_AsXFAPqCa8%2BuuRWq3xsg@mail.gmail.com> <CAFOYbcmUj24-bT29o_bu0ecRAfPud-tUZmUc1GW0SXZm0rSToQ@mail.gmail.com> <518576EF.90706@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
Hmmm, so its the stack, can that be easily increased Andre? Regards, Jack On Sat, May 4, 2013 at 2:00 PM, Andre Oppermann <andre@freebsd.org> wrote: > On 04.05.2013 22:47, Jack Vogel wrote: > >> Yes, I checked: #define IXGBE_TSO_SIZE 262140 >> >> So, the driver is not limiting you to 64K assuming you are using a >> version of recent vintage. >> > > The stack won't generate TCP and IP packets larger than 64K. However > the ethernet header gets prepended to it and bumps the overall packet > size as seen by the driver to 64K + sizeof(ether_hdr) and possibly > additional VLAN headers. If the bus_dma_tag size is set to 64K then > bus_dma mapping will fail for such maximum size packets. > > -- > Andre > > > Jack >> >> >> >> On Sat, May 4, 2013 at 1:41 PM, Jack Vogel <jfvogel@gmail.com> wrote: >> >> If you don't use TSO you will hurt your TX performance significantly fr= om >>> the tests that I've run. What exactly is the device you are using, I >>> don't >>> have the source in front of me now, but I'm almost sure that the limit = is >>> not 64K but 256K, or are you using some ancient version of the driver? >>> >>> Jack >>> >>> >>> >>> On Sat, May 4, 2013 at 1:30 PM, Richard Sharpe < >>> realrichardsharpe@gmail.com> wrote: >>> >>> On Sat, May 4, 2013 at 10:39 AM, Adrian Chadd <adrian@freebsd.org> >>>> wrote: >>>> >>>>> On 4 May 2013 06:52, Richard Sharpe <realrichardsharpe@gmail.com> >>>>> >>>> wrote: >>>> >>>>> Hi folks, >>>>>> >>>>>> I understand better why I am seeing EINVAL intermittently when sendi= ng >>>>>> data from Samba via SMB2. >>>>>> >>>>>> The ixgbe driver, for TSO reasons, limits the amount of data that ca= n >>>>>> be DMA'd to 65535 bytes. It returns EINVAL for any mbuf chain larger >>>>>> than that. >>>>>> >>>>>> The SO_SNDBUF for that socket is set to 131972. Mostly there is less >>>>>> than 64kiB of space available, so that is all TCP etc can put into t= he >>>>>> socket in one chain of mbufs. However, every now and then there is >>>>>> more than 65535 bytes available in the socket buffers, and we have a= n >>>>>> SMB packet that is larger than 65535 bytes, and we get hit. >>>>>> >>>>>> To confirm this I am going to set SO_SNDBUF back to the default of >>>>>> 65536 and test again. My repros are very reliable. >>>>>> >>>>>> However, I wondered if my only way around this if I want to continue >>>>>> to use SO_SNDBUF sizes larger than 65536 is to fragment large mbuf >>>>>> chains in the driver? >>>>>> >>>>> >>>>> Hm, is this is a problem without TSO? >>>>> >>>> >>>> We are using the card without TSO, so I am thinking of changing that >>>> limit to 131072 and retesting. >>>> >>>> I am currently testing with SO_SNDBUF=3D32768 and have not hit the >>>> problem. >>>> >>>> Is the problem that the NIC can't handle a frame that big, or a buffe= r >>>>> >>>> that big? >>>> >>>>> Ie - if you handed the hardware two descriptors of 64k each, for the >>>>> same IP datagram, will it complain? >>>>> >>>> >>>> I can't find any documentation, but it seems that with TSO it cannot >>>> handle a frame that big. Actually, since we are not using TSO, there >>>> really should not be a problem with larger frames. >>>> >>>> Or do you need to break it up into two separate IP datagrams, facing >>>>> the driver, with a maximum size of 64k each? >>>>> >>>> >>>> Not sure, but it looks like we need to do that. >>>> >>>> >>>> -- >>>> Regards, >>>> Richard Sharpe >>>> (=A6=F3=A5H=B8=D1=BC~=A1H=B0=DF=A6=B3=A7=F9=B1d=A1C--=B1=E4=BE=DE) >>>> ______________________________**_________________ >>>> freebsd-net@freebsd.org mailing list >>>> http://lists.freebsd.org/**mailman/listinfo/freebsd-net<http://lists.f= reebsd.org/mailman/listinfo/freebsd-net> >>>> To unsubscribe, send any mail to "freebsd-net-unsubscribe@**freebsd.or= g<freebsd-net-unsubscribe@freebsd.org> >>>> " >>>> >>> >>> >>> >>> ______________________________**_________________ >> freebsd-net@freebsd.org mailing list >> http://lists.freebsd.org/**mailman/listinfo/freebsd-net<http://lists.fre= ebsd.org/mailman/listinfo/freebsd-net> >> To unsubscribe, send any mail to "freebsd-net-unsubscribe@**freebsd.org<= freebsd-net-unsubscribe@freebsd.org> >> " >> >> >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAFOYbck9PV0f5bqxe2xhOKY=0F8GNG=5m6SCzizH4J%2Bjs%2By1yw>