Re: CVS commit: src/share/man/man4

[David Young <dyoung%pobox.com@localhost>]

On Thu, Apr 09, 2020 at 03:25:32PM +0900, SAITOH Masanobu wrote:
> On 2020/04/09 11:08, David Young wrote:
> > On Wed, Apr 08, 2020 at 11:01:52PM +0000, Jaromir Dolecek wrote:
> > > on I219 I observe about 35% transmit performance drop when tso4 enabled
> > 
> > This sounds familiar.  There was a bug affecting TCP segmentation
> > offload (I think) that we found at CoyotePoint.  ISTR
> > bus_dmamap_load_mbuf(9) failed with EFBIG because under some
> > circumstances the number of segments in the DMA map was too small
> > for the mbuf chain.  The driver would drop the whole mbuf chain
> > on the floor.  This showed up as terrible performance under some
> > circumstances---possibly when the TCP window grew long?  The solution
> > was to increase the number of DMA segments, *I think*.
> 
> m_defrag() was added to -current in September 2018, and 9.0,
> 8.1, post 7.2 have this code.

Thank you, that's just the change I was thinking of.

Dave

-- 
David Young
dyoung%pobox.com@localhost    Urbana, IL    (217) 721-9981