Date: 17 Mar 2001 19:33:10 +0100 From: Dag-Erling Smorgrav <des@ofug.org> To: Maxime Henrion <mux@qualys.com> Cc: arch@FreeBSD.org Subject: Re: Proposal for a new syscall Message-ID: <xzpzoekb5zt.fsf@flood.ping.uio.no> In-Reply-To: Maxime Henrion's message of "Sat, 17 Mar 2001 18:31:38 %2B0100" References: <20010317164411.A420@nebula.cybercable.fr> <xzpzoekcs3r.fsf@flood.ping.uio.no> <20010317173444.B420@nebula.cybercable.fr> <xzp4rwsco0r.fsf@flood.ping.uio.no> <20010317183137.C420@nebula.cybercable.fr>
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Maxime Henrion <mux@qualys.com> writes: > > > > > such a syscall in the kernel would allow to implement "zero-copy" > > > > > wherever it is feasible. > > > > No. It would save you two copies and a bunch of syscalls, but it > > > > wouldn't be real zero-copy, just "n-2 copy" instead of "n copy". > > > And if n == 2 ? > > It's never the case. I think the best you can do in userland is n = 3, > I'm talking about a syscall. Yes. I already told you that your proposed syscall would at best reduce the number of copies by two. Now I'm telling you that the minimum number of copies, without your proposed syscall, can't be less than 3. You do the math. > Why couldn't it be zero-copy if sendfile() already does this ? Sendfile(2) doesn't do zero-copy, it does 2-copy (in the best of cases). DES -- Dag-Erling Smorgrav - des@ofug.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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