Date: Tue, 3 Feb 2004 12:12:02 -0500 (EST) From: Robert Watson <rwatson@FreeBSD.org> To: Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?= <des@des.no> Cc: current@FreeBSD.org Subject: Re: Coalescing pipe allocation Message-ID: <Pine.NEB.3.96L.1040203121006.79056G-100000@fledge.watson.org> In-Reply-To: <xzpsmhs5c39.fsf@dwp.des.no>
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On Tue, 3 Feb 2004, Dag-Erling Sm=F8rgrav wrote: > Peter Edwards <peter.edwards@openet-telecom.com> writes: > > Dag-Erling Sm=F8rgrav wrote: > > > Peter Edwards <peter.edwards@openet-telecom.com> writes: > > > > How would one "shut down" one direction of the pipe and still maint= ain > > > > the other? I don't know how I can signal my intention not to read o= r > > > > write to the end I leave open... > > > man 2 shutdown > > Shutdown requires a socket, and won't play with pipes: >=20 > hmm, you're right. I was convinces that it was possible to shut down > one half of a pipe... At one point it may have been, when pipes were implemented using a socketpair. However, on recent FreeBSD, this is not the case. Many systems do implement pipes using socket pairs still, including Darwin.=20 Our pipe implementation will typically substantially out-perform socket pair implementations on the same hardware (often 150% or more for throughput). In fact, NetBSD recently picked up a modified version of our pipe implementation for this reason, I believe. However, it was side-by-side benchmarking of the resources required to allocate pipes vs. sockets that caused me to investigate optimizing the allocation process, as it still costs a lot more to allocate a pipe than a socket pair.=20 Robert N M Watson FreeBSD Core Team, TrustedBSD Projects robert@fledge.watson.org Senior Research Scientist, McAfee Research
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