From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754916AbcAVVLG (ORCPT ); Fri, 22 Jan 2016 16:11:06 -0500 Received: from mail-wm0-f48.google.com ([74.125.82.48]:35128 "EHLO mail-wm0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753954AbcAVVLD (ORCPT ); Fri, 22 Jan 2016 16:11:03 -0500 To: linux-kernel@vger.kernel.org From: Jakob Unterwurzacher Subject: Regression for mmap writes through FUSE in 4.2+ X-Enigmail-Draft-Status: N1110 Message-ID: <56A29AE3.8090606@gmail.com> Date: Fri, 22 Jan 2016 22:10:59 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I have noticed an annoying regression that was introduced in 4.2 and is still there in 4.4. mmap writes to FUSE filesystems are throttled down to basically zero. Reproducer: https://github.com/rfjakob/mmapwrite , testing against encfs: $ mmapwrite /tmp/encfs-mnt/foo 1 .................................................. 107.01 MB/s 2 .................................................. 101.98 MB/s [...] 68 .................................................. 106.79 MB/s 69 .................................................. 105.09 MB/s 70 .................................................. 2.02 MB/s 71 .................................................. 1.77 MB/s 72 .................................................. 0.42 MB/s 73 .................................... (hangs) I have tested kernels from 4.0 and this seems to have been introduced in 4.2: 4.0 ....... 140MB/s permanent 4.1 ....... 140MB/s permanent 4.2 ....... 100MB/s at the start, sudden slowdown to 1MB/s after ~5GB 4.3 ....... 100MB/s at the start, sudden slowdown to 1MB/s after ~1.5GB 4.4-rc4 ... 100MB/s at the start, slowly ramps down, 0.3MB/s after ~2GB 4.4 ....... 100MB/s at the start, sudden slowdown after ~3GB Is there a way to disable the throttling? Or at least exempt FUSE until there is a proper fix? Thanks, Jakob