From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx128.postini.com [74.125.245.128]) by kanga.kvack.org (Postfix) with SMTP id 57ED66B0036 for ; Fri, 28 Jun 2013 11:48:40 -0400 (EDT) Message-ID: <51CDB056.5090308@sr71.net> Date: Fri, 28 Jun 2013 08:48:38 -0700 From: Dave Hansen MIME-Version: 1.0 Subject: Re: [RFC][PATCH] mm: madvise: MADV_POPULATE for quick pre-faulting References: <20130627231605.8F9F12E6@viggo.jf.intel.com> <20130628054757.GA10429@gmail.com> In-Reply-To: <20130628054757.GA10429@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, linux-kernel@vger.kernel.org On 06/27/2013 10:47 PM, Zheng Liu wrote: >> I've been doing some testing involving large amounts of >> page cache. It's quite painful to get hundreds of GB >> of page cache mapped in, especially when I am trying to >> do it in parallel threads. This is true even when the >> page cache is already allocated and I only need to map >> it in. The test: >> >> 1. take 160 16MB files >> 2. clone 160 threads, mmap the 16MB files, and either >> a. walk through the file touching each page > > Why not change MAP_POPULATE flag in mmap(2)? Now it is only for private > mappings. But maybe we could let it support shared mapping. Adding that support to mmap() will certainly _help_ some folks. But, anything that mmap()s something is taking mmap_sem for write. That means that threaded apps doing mmap()/munmap() frequently are _not_ scalable. IOW, a process needing to do a bunch of MAP_POPULATEs isn't parallelizable, but one using this mechanism would be. -- 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