Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id <S132395AbRDXQjT>; Tue, 24 Apr 2001 12:39:19 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org
	id <S132338AbRDXQjK>; Tue, 24 Apr 2001 12:39:10 -0400
Received: from neon-gw.transmeta.com ([209.10.217.66]:48146 "EHLO
	neon-gw.transmeta.com") by vger.kernel.org with ESMTP
	id <S132416AbRDXQjA>; Tue, 24 Apr 2001 12:39:00 -0400
Date: Tue, 24 Apr 2001 09:38:08 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: Ingo Molnar <mingo@elte.hu>
cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Linux Kernel List <linux-kernel@vger.kernel.org>, linux-mm@kvack.org,
        Marcelo Tosatti <marcelo@conectiva.com.br>,
        Rik van Riel <riel@conectiva.com.br>,
        Szabolcs Szakacsits <szaka@f-secure.com>
Subject: Re: [patch] swap-speedup-2.4.3-B3
In-Reply-To: <Pine.LNX.4.30.0104240714200.1227-100000@elte.hu>
Message-ID: <Pine.LNX.4.21.0104240932570.15791-100000@penguin.transmeta.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org


On Tue, 24 Apr 2001, Ingo Molnar wrote:
> 
> the latest swap-speedup patch can be found at:

Please don't add more of those horrible "wait" arguments.

Make two different versions of a function instead. It's going to clean up
and simplify the code, and there really isn't any reason to do what you're
doing.

You should split up the logic differently: if you want to wait for the
page, then DO so:

	page = lookup_swap_cache(..);
	if (page) {
		wait_for_swap_cache:valid(page);
		.. use page ..
	}

Note how much more readable and UNDERSTANDABLE the above is, compared to

	page = lookup_swap_cache(..., 1);
	if (page) {
		...

and note also how splitting up the waiting will

 - simplify the swap cache lookup function, making it faster for people
   who do _NOT_ want to wait.

 - make it easier to statically check the correctness of programs by just
   eye-balling them ("Hey, he's calling 'wait' with the spinlock held").

 - more easily moving the wait around, allowing for more concurrency.

Basically, I don't want to mix synchronous and asynchronous
interfaces. Everything should be asynchronous by default, and waiting
should be explicit.

		Linus

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/