Date: Tue, 27 May 2003 15:25:31 +0400 (MSD) From: Igor Sysoev <is@rambler-co.ru> To: Peter Jeremy <peterjeremy@optushome.com.au> Cc: arch@freebsd.org Subject: Re: sendfile(2) SF_NOPUSH flag proposal Message-ID: <Pine.BSF.4.21.0305271513120.46491-100000@is> In-Reply-To: <20030527102806.GC44520@cirb503493.alcatel.com.au>
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On Tue, 27 May 2003, Peter Jeremy wrote: > 2) The new feature provides significant performance benefit. In this > case, I believe the overhead of calling setsockopt(2) is negligible > so the performance gain would be negligible. I think the calling setsockopt(TCP_NOPUSH, 1) syscall has huge overhead as compared to several C operators inside sendfile(2). The turing TF_NOPUSH off has almost the same overhead as setsockopt(TCP_NOPUSH, 0) if you need to call tcp_output(tp) inside sendfile(2) and has no overhead at all if you do not need to call it. > At this stage, I would suggest that you need to do better than "the > change is cheap" to justify adding this feature. Can you quantify > the performance benefits, or provide some other justification? My point is not "the cheap change" but "the cheap overhead". Igor Sysoev http://sysoev.ru/en/
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