Date: Tue, 25 Nov 2003 01:17:34 -0700 (MST) From: "M. Warner Losh" <imp@bsdimp.com> To: peterjeremy@optushome.com.au Cc: gallatin@cs.duke.edu Subject: Re: 40% slowdown with dynamic /bin/sh Message-ID: <20031125.011734.118629079.imp@bsdimp.com> In-Reply-To: <20031125080155.GC76478@server.vk2pj.dyndns.org> References: <200311242125.13786.sam@errno.com> <20031124.231607.128865107.imp@bsdimp.com> <20031125080155.GC76478@server.vk2pj.dyndns.org>
next in thread | previous in thread | raw e-mail | index | archive | help
In message: <20031125080155.GC76478@server.vk2pj.dyndns.org>
Peter Jeremy <peterjeremy@optushome.com.au> writes:
: On Mon, Nov 24, 2003 at 11:16:07PM -0700, M. Warner Losh wrote:
: >Hmmmm, It looks like the hit is less than 10% in the fork intensive
: >test I just wrote:
: >
: >#!/bin/sh
: >for i in 0 1 2 3 4 5 6 7 8 9; do
: > for j in 0 1 2 3 4 5 6 7 8 9; do
: > for k in 0 1 2 3 4 5 6 7 8 9; do
: > for l in 0 1 2 3 4 5 6 7 8 9; do
: > for m in 0 1 2 3 4 5 6 7 8 9; do
: > for n in 0 1 2 3 4 5 6 7 8 9; do
: > true;
: >done; done; done; done; done; done;
:
: Unless you've done something wierd to your /bin/sh, "true" is a
: builtin. This test just to measures the ongoing runtime overhead
: of a dynamic executable (ie PIC code). Drew's test was measuring
: the startup overhead.
True. However, I get very similar numbers of I change it to
/usr/bin/true (12% slower). /bin/sh usually fork+exec things other
/bin/sh.
: >Clearly dynamic is slower, but it is more like 11% slower (10.67%) on
: >the average than 40% slower. I think this would be a more typical
: >usage pattern.
:
: You have measured different things. Drew's test shows that a dynamic
: /bin/sh tahes about 40% longer to start. Your test shows that once
: started, it runs about 11% slower. And the 11% slower is _very_
: worrying since it is probably more widely applicable than just /bin/sh.
Dynamically linked prorgrams tend to be a few percent slower than
their static counterparts due to PIC code typically being slower than
non-PIC code. There's nothing new here.
Clearly there are problems to look into, but it isn't the end of the
world.
Warner
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20031125.011734.118629079.imp>