Date: Thu, 21 May 2020 21:42:50 +0000 (UTC) From: Richard Scheffenegger <rscheff@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r361348 - head/sys/netinet/cc Message-ID: <202005212142.04LLgobu003967@repo.freebsd.org>
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Author: rscheff Date: Thu May 21 21:42:49 2020 New Revision: 361348 URL: https://svnweb.freebsd.org/changeset/base/361348 Log: DCTCP: update alpha only once after loss recovery. In mixed ECN marking and loss scenarios it was found, that the alpha value of DCTCP is updated two times. The second update happens with freshly initialized counters indicating to ECN loss. Overall this leads to alpha not adjusting as quickly as expected to ECN markings, and therefore lead to excessive loss. Reported by: Cheng Cui Reviewed by: chengc_netapp.com, rrs, tuexen (mentor) Approved by: tuexen (mentor) MFC after: 2 weeks Sponsored by: NetApp, Inc. Differential Revision: https://reviews.freebsd.org/D24817 Modified: head/sys/netinet/cc/cc_dctcp.c Modified: head/sys/netinet/cc/cc_dctcp.c ============================================================================== --- head/sys/netinet/cc/cc_dctcp.c Thu May 21 21:33:15 2020 (r361347) +++ head/sys/netinet/cc/cc_dctcp.c Thu May 21 21:42:49 2020 (r361348) @@ -154,10 +154,8 @@ dctcp_ack_received(struct cc_var *ccv, uint16_t type) * Update the fraction of marked bytes at the end of * current window size. */ - if ((IN_FASTRECOVERY(CCV(ccv, t_flags)) && - SEQ_GEQ(ccv->curack, CCV(ccv, snd_recover))) || - (!IN_FASTRECOVERY(CCV(ccv, t_flags)) && - SEQ_GT(ccv->curack, dctcp_data->save_sndnxt))) + if (!IN_FASTRECOVERY(CCV(ccv, t_flags)) && + SEQ_GT(ccv->curack, dctcp_data->save_sndnxt)) dctcp_update_alpha(ccv); } else newreno_cc_algo.ack_received(ccv, type);
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