Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 13 Feb 2001 06:17:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 13 Feb 2001 06:16:58 -0500 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:49416 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id ; Tue, 13 Feb 2001 06:16:51 -0500 From: Russell King Message-Id: <200102131116.f1DBGFx02086@flint.arm.linux.org.uk> Subject: Re: [PATCH] swapin flush cache bug To: gniibe@m17n.org (NIIBE Yutaka) Date: Tue, 13 Feb 2001 11:16:14 +0000 (GMT) Cc: marcelo@conectiva.com.br (Marcelo Tosatti), torvalds@transmeta.com (Linus Torvalds), alan@lxorguk.ukuu.org.uk (Alan Cox), linux-kernel@vger.kernel.org (lkml) In-Reply-To: <200102131053.TAA11808@mule.m17n.org> from "NIIBE Yutaka" at Feb 13, 2001 07:53:11 PM X-Location: london.england.earth.mulky-way.universe X-Mailer: ELM [version 2.5 PL3] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org NIIBE Yutaka writes: > My case (SH-4) is: virtual address indexed, physical address tagged cache > (which has alias issue). vivt caches have the same alias issue. > Suppose there's I/O to the physical page P asynchronously, and the > page is placed in the swap cache. Unless someone else (Rik/DaveM) says otherwise, it is my understanding that any IO for page P will only ever be a write to disk. Therefore, when you get a copy of the page from the swap cache, the physical memory for that page is the same as it was when the process was using it last. > It remains cache entry, say, indexed kernel virtual address K. Then, > process maps P at U. U and K (may) indexes differently. The process > will get the data from memory (not the one in the cashe), if it's not > flushed. The data from memory will still be up to date though. However, I agree that you will end up with cache aliases. I will also end up with cache aliases. The question now is, do these aliases really matter? On my caches, the answer is no because they're not marked dirty, and therefore will get dropped from the cache without writeback to memory. If your cache doesn't write back clean cache data to memory, then you should also behave well. However, that said, someone more experienced with the Linux MM should comment. -- Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux http://www.arm.linux.org.uk/personal/aboutme.html - 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/