Date: Fri, 6 Nov 2015 20:46:57 +0000 From: "Cui, Cheng" <Cheng.Cui@netapp.com> To: "hselasky@FreeBSD.org" <hselasky@FreeBSD.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: question about trimning data "len" conditions in TSO in tcp_output.c Message-ID: <C44A2900-40E0-41EF-83B1-6DD4B31DABD5@netapp.com>
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Hello Hans, Sorry if my previous email does not reach you because of a bad subject. This is Cheng Cui. I am reading the CURRENT FreeBSD code in tcp_output.c, and find this question regarding your change in revision 271946. https://svnweb.freebsd.org/base/head/sys/netinet/tcp_output.c?r1=271946&r2=271945&pathrev=271946 trim data "len" under TSO: 885 /* 886 * Prevent the last segment from being 887 * fractional unless the send sockbuf can be 888 * emptied: 889 */ 890 max_len = (tp->t_maxopd - optlen); 891 if ((off + len) < sbavail(&so->so_snd)) { <== 892 moff = len % max_len; 893 if (moff != 0) { 894 len -= moff; 895 sendalot = 1; 896 } 897 } Is there a specific reason that it should skip trimming the data "len" under the condition of "(off + len) == sbavail(&so->so_snd)" in TSO? Because I am wondering if we can trim the data "len" directly without checking the "(off + len)" condition. Thanks, --Cheng Cui NetApp Scale Out Networking
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