Date: Tue, 24 Apr 2007 00:53:55 -0400 From: Kris Kennaway <kris@obsecurity.org> To: Tim Kientzle <kientzle@freebsd.org> Cc: current@freebsd.org, "Jesper B. Rosenkilde" <jbr@humppa.dk> Subject: Re: Suggestions on Avoiding syscall Overhead Message-ID: <20070424045355.GA6330@xor.obsecurity.org> In-Reply-To: <462D821F.6030707@freebsd.org> References: <f126fae00704221639l68095de1ye7ce9ba3d921bf20@mail.gmail.com> <20070423113400.GC28587@gw.humppa.dk> <462CD251.9060105@freebsd.org> <20070423161711.GV39474@elvis.mu.org> <462D821F.6030707@freebsd.org>
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On Mon, Apr 23, 2007 at 09:05:51PM -0700, Tim Kientzle wrote: > >>>>We can have 3 type of pages mapped into one process's address map. > >>>>1. System wide global readonly page which will help on these syscalls: > >>>>gethostname,getdomainname,uname > >>>>2. Per process Readonly page. (change will still through standard > >>>>syscall) > >>>>help on the syscalls: > >>>>getuid, geteuid, getpid,getgid, getegid, getpgrp, > >> > >>I don't really understand this suggestion. > >>Do any real programs call these syscalls very often? > > > >There is indeed more and more programs calling some syscalls a > >*lot* .... MySQL calls gettimeofday() so much that changing > >the timer used on a system can lead to a very observable performance > >improvement. Similarly, PostgreSQL calls setproctitle() a lot ... > > Accelerating gettimeofday() makes a lot of sense; I've seen a > lot of programs that call it very often. > > I'm not convinced about calls such as getuid() and gethostname(), > though. Putting this kind of information in userspace > introduces forward-compatibility concerns. People do > statically link against libc, so you have to make sure that libc can > find this information even when running on future kernels. > That makes each such call a tricky maintenance issue. Well you will have to keep compatibility syscalls anyway, because not everything even links to libc ;) Kris
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