On 08/25/2015 10:16 PM, Zhang, Helin wrote: > >> -----Original Message----- >> From: Vlad Zolotarov [mailto:vladz at cloudius-systems.com] >> Sent: Tuesday, August 25, 2015 11:53 AM >> To: Zhang, Helin >> Cc: Lu, Wenzhuo; dev at dpdk.org >> Subject: Re: [dpdk-dev] [PATCH v1] ixgbe_pmd: forbid tx_rs_thresh above 1 for >> all NICs but 82598 >> >> >> >> On 08/25/15 21:43, Zhang, Helin wrote: >>> Hi Vlad >>> >>> I think this could possibly be the root cause of your TX hang issue. >>> Please try to limit the number to 8 or less, and then see if the issue >>> will still be there or not? >>> >> Helin, the issue has been seen on x540 devices. Pls., see a chapter >> 7.2.1.1 of x540 devices spec: >> >> A packet (or multiple packets in transmit segmentation) can span any number >> of >> buffers (and their descriptors) up to a limit of 40 minus WTHRESH minus 2 >> (see >> Section 7.2.3.3 for Tx Ring details and section Section 7.2.3.5.1 for WTHRESH >> details). For best performance it is recommended to minimize the number of >> buffers as possible. >> >> Could u, pls., clarify why do u think that the maximum number of data >> buffers is >> limited by 8? > OK, i40e hardware is 8, so I'd assume x540 could have a similar one. Yes, in > your case, > the limit could be around 38, right? > Could you help to make sure there is no packet to be transmitted uses more > than > 38 descriptors? > I heard that there is a similar hang issue on X710 if using more than 8 > descriptors for > a single packet. I am wondering if the issue is similar on x540. > >
I believe that the ixgbe Linux driver does not limit packets to 8 fragments, so apparently the hardware is capable.
