Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764753AbZDBWJh (ORCPT ); Thu, 2 Apr 2009 18:09:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762005AbZDBWJ0 (ORCPT ); Thu, 2 Apr 2009 18:09:26 -0400 Received: from srv5.dvmed.net ([207.36.208.214]:51459 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758952AbZDBWJZ (ORCPT ); Thu, 2 Apr 2009 18:09:25 -0400 Message-ID: <49D53787.9060503@garzik.org> Date: Thu, 02 Apr 2009 18:09:11 -0400 From: Jeff Garzik User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Linus Torvalds CC: Andrew Morton , David Rees , Janne Grunau , Lennart Sorensen , Theodore Tso , Jesper Krogh , Linux Kernel Mailing List Subject: Re: Linux 2.6.29 References: <20090325183011.GN32307@mit.edu> <20090325220530.GR32307@mit.edu> <20090326171148.9bf8f1ec.akpm@linux-foundation.org> <20090326174704.cd36bf7b.akpm@linux-foundation.org> <20090326182519.d576d703.akpm@linux-foundation.org> <20090401210337.GB3797@csclub.uwaterloo.ca> <20090402110532.GA5132@aniel> <72dbd3150904020929w46c6dc0bs4028c49dd8fa8c56@mail.gmail.com> <20090402094247.9d7ac19f.akpm@linux-foundation.org> In-Reply-To: Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.4 (----) X-Spam-Report: SpamAssassin version 3.2.5 on srv5.dvmed.net summary: Content analysis details: (-4.4 points, 5.0 required) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1541 Lines: 42 Linus Torvalds wrote: > > On Thu, 2 Apr 2009, Linus Torvalds wrote: >> On Thu, 2 Apr 2009, Andrew Morton wrote: >>> A suitable design for the streaming might be, every 4MB: >>> >>> - run sync_file_range(SYNC_FILE_RANGE_WRITE) to get the 4MB underway >>> to the disk >>> >>> - run fadvise(POSIX_FADV_DONTNEED) against the previous 4MB to >>> discard it from pagecache. >> Here's an example. I call it "overwrite.c" for obvious reasons. > > Oh, except my example doesn't do the fadvise. Instead, I make sure to > throttle the writes and the old range with > > SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER > > which makes sure that the old pages are easily dropped by the VM - and > they will be, since they end up always being on the cold list. Dumb VM question, then: I understand the logic behind the write-throttling part (some of my own userland code does something similar), but, Does this imply adding fadvise to your overwrite.c example is (a) not noticable, (b) potentially less efficient, (c) potentially more efficient? Or IOW, does fadvise purely put pages on the cold list as your sync_file_range incantation does, or something different? Thanks, Jeff, who is already using sync_file_range in some server-esque userland projects -- 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/