From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx151.postini.com [74.125.245.151]) by kanga.kvack.org (Postfix) with SMTP id 221876B0032 for ; Wed, 7 Aug 2013 13:40:54 -0400 (EDT) Message-ID: <520286A4.1020101@intel.com> Date: Wed, 07 Aug 2013 10:40:52 -0700 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [RFC 0/3] Add madvise(..., MADV_WILLWRITE) References: <20130807134058.GC12843@quack.suse.cz> In-Reply-To: <20130807134058.GC12843@quack.suse.cz> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: Andy Lutomirski , linux-mm@kvack.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org On 08/07/2013 06:40 AM, Jan Kara wrote: > One question before I look at the patches: Why don't you use fallocate() > in your application? The functionality you require seems to be pretty > similar to it - writing to an already allocated block is usually quick. One problem I've seen is that it still costs you a fault per-page to get the PTEs in to a state where you can write to the memory. MADV_WILLNEED will do readahead to get the page cache filled, but it still leaves the pages unmapped. Those faults get expensive when you're trying to do a couple hundred million of them all at once. -- 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/ . Don't email: email@kvack.org