From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v1] ixgbe_pmd: forbid tx_rs_thresh above 1 for all NICs but 82598 Date: Tue, 25 Aug 2015 22:23:36 +0300 Message-ID: <55DCC0B8.9000809@cloudius-systems.com> References: <1439489195-31553-1-git-send-email-vladz@cloudius-systems.com> <55CD7EA5.6060100@cloudius-systems.com> <6A0DE07E22DDAD4C9103DF62FEBC0909D3E116@shsmsx102.ccr.corp.intel.com> <55DCB975.2030000@cloudius-systems.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "dev@dpdk.org" To: "Zhang, Helin" , Vlad Zolotarov Return-path: Received: from mail-wi0-f170.google.com (mail-wi0-f170.google.com [209.85.212.170]) by dpdk.org (Postfix) with ESMTP id 9A83B5952 for ; Tue, 25 Aug 2015 21:23:49 +0200 (CEST) Received: by widdq5 with SMTP id dq5so24127453wid.0 for ; Tue, 25 Aug 2015 12:23:49 -0700 (PDT) In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 08/25/2015 10:16 PM, Zhang, Helin wrote: > >> -----Original Message----- >> From: Vlad Zolotarov [mailto:vladz@cloudius-systems.com] >> Sent: Tuesday, August 25, 2015 11:53 AM >> To: Zhang, Helin >> Cc: Lu, Wenzhuo; dev@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.