From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933100Ab3BTAnh (ORCPT ); Tue, 19 Feb 2013 19:43:37 -0500 Received: from mail-qa0-f48.google.com ([209.85.216.48]:62333 "EHLO mail-qa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932691Ab3BTAng (ORCPT ); Tue, 19 Feb 2013 19:43:36 -0500 Message-ID: <51241C32.3050500@gmail.com> Date: Wed, 20 Feb 2013 08:43:30 +0800 From: Will Huck User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: Hugh Dickins CC: Li Haifeng , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: Should a swapped out page be deleted from swap cache? References: <5122C9B3.10306@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/20/2013 03:06 AM, Hugh Dickins wrote: > On Tue, 19 Feb 2013, Will Huck wrote: >> Another question: > I don't see the connection to deleting a swapped out page from swap cache. > >> Why kernel memory mapping use direct mapping instead of kmalloc/vmalloc which >> will setup mapping on demand? > I may misunderstand you, and "kernel memory mapping". > > kmalloc does not set up a mapping, it uses the direct mapping already set up. > > It would be circular if the basic page allocation primitives used kmalloc, > since kmalloc relies on the basic page allocation primitives. > > vmalloc is less efficient than using the direct mapping (repeated setup > and teardown, no use of hugepages), but necessary when you want a larger Is there tlb flush in setup and teardown process? and they also expensive? > virtual array than you're likely to find from the buddy allocator. > > Hugh