From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 From: Nikolaus Rath To: fuse-devel@lists.sourceforge.net, linux-fsdevel , linux-kernel , Miklos Szeredi Subject: fuse: max_background and congestion_threshold settings Date: Tue, 15 Nov 2016 08:18:42 -0800 Message-ID: <87oa1g90nx.fsf@thinkpad.rath.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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.=20 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 --=20 GPG encrypted emails preferred. Key id: 0xD113FCAC3C4E599F Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F =C2=BBTime flies like an arrow, fruit flies like a Banana.=C2= =AB