From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: mmap and raw disk devices... References: <3BCEFC46.9E8FEF7A@htec.demon.co.uk> From: ebiederm@xmission.com (Eric W. Biederman) Date: 19 Oct 2001 08:46:05 -0600 In-Reply-To: <3BCEFC46.9E8FEF7A@htec.demon.co.uk> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Christopher Quinn Cc: linux-mm@kvack.org List-ID: Christopher Quinn writes: > Hello list, > > I tried to mmap a disk partition raw device which failed. > Can anyone tell me the reason mmap does not support such a > device? > I would have thought a mmap/raw-device combination to be ideal as > a basis for a high performance database system. > > I know there is the option of managing memory<->disk movements > oneself, but my understanding is that handling page-faults via > signal trap handling is *very* expensive. Far better to leave > such matters in the hands of the OS. > > I suspect there is some fundamental reason for not mmap'ing raw > devices that is patently obvious to everyone but me! mmap goes through the page cache. It should work in 2.4.10+ though someone might not have enabled it. Eric -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/