From: Matt Mackall <mpm@selenic.com>
To: Rick Jones <rick.jones2@hp.com>
Cc: netdev@oss.sgi.com
Subject: Re: [RFC] TCP congestion schedulers
Date: Wed, 30 Mar 2005 01:41:24 -0800 [thread overview]
Message-ID: <20050330094124.GG25554@waste.org> (raw)
In-Reply-To: <4249A570.90709@hp.com>
On Tue, Mar 29, 2005 at 10:58:56AM -0800, Rick Jones wrote:
> <excerpt>
>
> McKinley-type cores (includes Madison, etc.)
> do not have indirect branch target hardware. Instead, indirect
> branches are executed as follows:
[...]
> (1) To _guarantee_ correct prediction, the branch register has to be
> loaded way before the indirect branch direction (at least 6
> front-end L1I cache accesses; which is up to 6 bundle-pairs or 36
> instructions, I believe).
That's horrendous. Indirect calls are a performance win vs conditional
branching on more sensible architectures and it's used quite
extensively in various parts of the kernel. It really makes one wonder
if dealing with this quirk is worth the trouble.
--
Mathematics is the supreme nostalgia of our time.
next prev parent reply other threads:[~2005-03-30 9:41 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-02-23 21:30 [PATCH] select congestion control with one sysctl Baruch Even
2005-02-23 21:57 ` David S. Miller
2005-02-24 0:23 ` Stephen Hemminger
2005-02-24 0:33 ` David S. Miller
2005-02-26 9:41 ` Arnaldo Carvalho de Melo
[not found] ` <421D30FA.1060900@ev-en.org>
[not found] ` <20050225120814.5fa77b13@dxpl.pdx.osdl.net>
[not found] ` <20050309210442.3e9786a6.davem@davemloft.net>
[not found] ` <4230288F.1030202@ev-en.org>
[not found] ` <20050310182629.1eab09ec.davem@davemloft.net>
[not found] ` <20050311120054.4bbf675a@dxpl.pdx.osdl.net>
[not found] ` <20050311201011.360c00da.davem@davemloft.net>
2005-03-14 23:17 ` [RFC] TCP congestion schedulers Stephen Hemminger
2005-03-15 19:54 ` John Heffner
2005-03-15 22:16 ` John Heffner
2005-03-18 4:12 ` David S. Miller
2005-03-18 12:53 ` Arnaldo Carvalho de Melo
2005-03-18 13:43 ` jamal
2005-03-18 16:13 ` Arnaldo Carvalho de Melo
2005-03-18 16:45 ` Stephen Hemminger
2005-03-18 16:59 ` Arnaldo Carvalho de Melo
2005-03-19 20:19 ` Andi Kleen
2005-03-21 21:25 ` John Heffner
2005-03-21 21:51 ` David S. Miller
2005-03-21 22:30 ` Baruch Even
2005-03-22 0:10 ` Rick Jones
2005-03-22 1:41 ` Olaf Kirch
2005-03-22 7:41 ` Andi Kleen
2005-03-28 23:51 ` Stephen Hemminger
2005-03-29 15:25 ` Andi Kleen
2005-03-29 17:17 ` Stephen Hemminger
2005-03-29 18:58 ` Rick Jones
2005-03-30 9:41 ` Matt Mackall [this message]
2005-03-29 19:32 ` John Heffner
2005-03-29 20:03 ` David S. Miller
2005-03-29 20:09 ` Rick Jones
2005-04-08 19:33 ` John Heffner
2005-04-08 20:20 ` Rick Jones
2005-02-24 1:05 ` [PATCH] select congestion control with one sysctl Daniele Lacamera
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