Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753651AbcKOQSs (ORCPT ); Tue, 15 Nov 2016 11:18:48 -0500 Received: from out4-smtp.messagingengine.com ([66.111.4.28]:47300 "EHLO out4-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751360AbcKOQSq (ORCPT ); Tue, 15 Nov 2016 11:18:46 -0500 X-ME-Sender: X-Sasl-enc: ctgHmiLn48D5EbYb0h9KyvpMONtid+wiIUGBA7WNWyGg 1479226723 From: Nikolaus Rath To: fuse-devel@lists.sourceforge.net, linux-fsdevel , linux-kernel , Miklos Szeredi Subject: fuse: max_background and congestion_threshold settings Mail-Copies-To: never Mail-Followup-To: fuse-devel@lists.sourceforge.net, linux-fsdevel , linux-kernel , Miklos Szeredi Date: Tue, 15 Nov 2016 08:18:42 -0800 Message-ID: <87oa1g90nx.fsf@thinkpad.rath.org> User-Agent: Gnus/5.130014 (Ma Gnus v0.14) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id uAFGIr7L029272 Content-Length: 867 Lines: 23 Hello, Could someone explain to me the meaning of the max_background and congestion_threshold settings of the fuse module? At first I assumed that max_background specifies the maximum number of pending requests (i.e., requests that have been send to userspace but for which no reply was received yet). But looking at fs/fuse/dev.c, it looks as if not every request is included in this number. I also figured out that if the number of background requests (whatever they are) exceeds the congestion threshold, fuse calls set_bdi_congested() for the backing device. But what does this do? And does this become a no-op if there is no backing device? Thanks, -Nikolaus -- GPG encrypted emails preferred. Key id: 0xD113FCAC3C4E599F Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F »Time flies like an arrow, fruit flies like a Banana.«