Date: Wed, 05 Jun 2013 15:51:47 +1000 From: Lawrence Stewart <lstewart@freebsd.org> To: Andre Oppermann <andre@FreeBSD.org> Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org, cperciva@FreeBSD.org Subject: Re: svn commit: r251297 - head/sys/dev/xen/netfront Message-ID: <51AED1F3.2060003@freebsd.org> In-Reply-To: <201306031300.r53D0XUx092178@svn.freebsd.org> References: <201306031300.r53D0XUx092178@svn.freebsd.org>
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On 06/03/13 23:00, Andre Oppermann wrote: > Author: andre > Date: Mon Jun 3 13:00:33 2013 > New Revision: 251297 > URL: http://svnweb.freebsd.org/changeset/base/251297 > > Log: > Specify a maximum TSO length limiting the segment chain to what the > Xen host side can handle after defragmentation. > > This prevents the driver from throwing away too long TSO chains and > improves the performance on Amazon AWS instances with 10GigE virtual > interfaces to the normally expected throughput. > > Submitted by: cperciva (earlier version) > Reviewed by: cperciva > Tested by: cperciva > MFC after: 1 week > > Modified: > head/sys/dev/xen/netfront/netfront.c > > Modified: head/sys/dev/xen/netfront/netfront.c > ============================================================================== > --- head/sys/dev/xen/netfront/netfront.c Mon Jun 3 12:55:13 2013 (r251296) > +++ head/sys/dev/xen/netfront/netfront.c Mon Jun 3 13:00:33 2013 (r251297) > @@ -134,6 +134,7 @@ static const int MODPARM_rx_flip = 0; > * to mirror the Linux MAX_SKB_FRAGS constant. > */ > #define MAX_TX_REQ_FRAGS (65536 / PAGE_SIZE + 2) > +#define NF_TSO_MAXBURST ((IP_MAXPACKET / PAGE_SIZE) * MCLBYTES) For posterity's sake, can you and/or Colin please elaborate on how this value was determined and what it is dependent upon? Could a newer version of Xen remove the need for this reduced limit? Cheers, Lawrence
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