Date: Wed, 4 Jul 2007 15:48:39 +0200 From: "Nicolas Cormier" <n.cormier@gmail.com> To: "Robert Watson" <rwatson@freebsd.org> Cc: freebsd-hackers@freebsd.org Subject: Re: p_vmspace in syscall Message-ID: <c4630b800707040648k560ad15bgb0e198bef7899adf@mail.gmail.com> In-Reply-To: <20070704141257.M37059@fledge.watson.org> References: <c4630b800707020954s4aa0be68t2d5f3eb864f2dda5@mail.gmail.com> <20070704091349.T42421@fledge.watson.org> <c4630b800707040200n4a6de4f5j2008f60fefb149e6@mail.gmail.com> <20070704120624.W37059@fledge.watson.org> <c4630b800707040604r296632dap562f6e6bc0bfe330@mail.gmail.com> <20070704141257.M37059@fledge.watson.org>
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On 7/4/07, Robert Watson <rwatson@freebsd.org> wrote: > What do you mean by a network allocator? How do you plan to use these pages? First I just want to access a local copy of a distant buffer. After the goal is to share memory between hosts (no concurrent access). > If you haven't already, you should look at the zero-copy socket code in > uipc_cow.c. The main criticism of this approach has been that it uses > copy-on-write, leading to potential IPIs for VM shootdowns, etc. An > alternative, more along the lines of IO-Lite, would be to allow user space to > explicitly abandon the page on send, then map a new page to replace it. In > which case you might consider a variation on the send system call that accepts > only page-aligned arguments and has the effect of unmapping the pages that are > sent. In neither case, on the transmit side, does this require an > modification to the kernel memory allocator. > > The receive side has always been more tricky to deal with... > Ok I will take a look at uipc_cow.c, Thank you -- Nicolas Cormier
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