On 2020/04/10 2:42, David Young wrote:
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.

You're welcome.
Some drivers still have no m_defrag() code, so we should add it
to them().


                SAITOH Masanobu (msai...@execsw.org

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