From owner-freebsd-hackers Tue May 27 20:01:05 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id UAA18658 for hackers-outgoing; Tue, 27 May 1997 20:01:05 -0700 (PDT) Received: from mailer.syr.edu (mailer.syr.edu [128.230.20.20]) by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id UAA18653 for ; Tue, 27 May 1997 20:01:03 -0700 (PDT) Received: from rodan.syr.edu by mailer.syr.edu (LSMTP for Windows NT v1.1a) with SMTP id <0.DAF56870@mailer.syr.edu>; Tue, 27 May 1997 23:01:05 -0400 Received: from localhost (cmsedore@localhost) by rodan.syr.edu (8.8.5/8.8.5) with SMTP id XAA12705; Tue, 27 May 1997 23:01:01 -0400 (EDT) X-Authentication-Warning: rodan.syr.edu: cmsedore owned process doing -bs Date: Tue, 27 May 1997 23:01:00 -0400 (EDT) From: Christopher Sedore X-Sender: cmsedore@rodan.syr.edu To: "Justin T. Gibbs" cc: "Ron G. Minnich" , FreeBSD-Hackers@FreeBSD.ORG Subject: Re: async socket stuff In-Reply-To: <199705272205.QAA08460@pluto.plutotech.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk On Tue, 27 May 1997, Justin T. Gibbs wrote: > >Now, in the case of a 10MB file, you've essentially saved 20MB worth of > >memory bandwidth/time for transfer (since the data has to be copied into > >user space on read, and back again on write), plus 160*2=320-1=319 system > >calls avoided. > > If you use an async I/O facility, there is no additional copy since you've > pre-allocated the buffer and I/O from the file goes directly into and out > of your user space buffer. Since your main complaint seems to be memory > bandwidth and the system call overhead is really quite small (FreeBSD can > do thousands of system calls a second on a P90), I think that async I/O > would completely solve your problem. There is already work underway to > bring async I/O to FreeBSD. I didn't know whether the async implementation would provide this or not. I still view too many syscalls as undesirable. This overhead seems a shame. -Chris