From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5CB88C433FE for ; Tue, 11 Oct 2022 01:23:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230297AbiJKBX1 (ORCPT ); Mon, 10 Oct 2022 21:23:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49242 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230211AbiJKBXI (ORCPT ); Mon, 10 Oct 2022 21:23:08 -0400 Received: from 66-220-144-178.mail-mxout.facebook.com (66-220-144-178.mail-mxout.facebook.com [66.220.144.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2DC2D83054 for ; Mon, 10 Oct 2022 18:22:46 -0700 (PDT) Received: by dev1180.prn1.facebook.com (Postfix, from userid 425415) id E1F2834BDD53; Mon, 10 Oct 2022 18:00:58 -0700 (PDT) From: Stefan Roesch To: kernel-team@fb.com, linux-block@vger.kernel.org, linux-mm@kvack.org Cc: shr@devkernel.io, axboe@kernel.dk, clm@meta.com Subject: [RFC PATCH v1 00/14] mm/block: add bdi sysfs knobs Date: Mon, 10 Oct 2022 18:00:30 -0700 Message-Id: <20221011010044.851537-1-shr@devkernel.io> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org At meta network block devices (nbd) are used to implement remote block st= orage. In testing and during production it has been observed that these network block devic= es can consume a huge portion of the dirty writeback and writeback can take a considerab= le time. To give stricter limits, I'm proposing the following changes and new sysf= s knobs: 1) strictlimit knob Currently the max_ratio knob exists to limit the dirty_memory. However = this knob only applies once (dirty_ratio + dirty_background_ratio) / 2 has been r= eached. With the BDI_CAP_STRICTLIMIT flag, the max_ratio can be applied without= reaching that limit. This change exposes that knob. This knob can also be useful for NFS, fuse filesystems and USB devices. 2) Part of 10000 internal calculation The max_ratio is based on percentage. With the current machine sizes pe= rcentage values can be very high (1% of a 256GB main memory is already 2.5GB). T= his change uses part of 10000 instead of percentages for the internal calculations= . 3) Introduce two new knobs: min_bytes and max_bytes. Currently all calculations are based on ratio, but for a user it often = more convenient to specify a limit in bytes. The new knobs will not store by= tes values, instead they will translate the byte value to a corresponding ratio. As= the internal values are now part of 10000, the ratio is closer to the specified valu= e. However the value should be more seen as an approximation as it can fluctuate o= ver time. Stefan Roesch (14): mm: add bdi_set_strict_limit() function mm: Add new knob /sys/class/bdi//strict_limit mm: document new /sys/class/bdi//strict_limit knob mm: Use part per 10000 for bdi ratios. mm: add bdi_get_max_bytes() function mm: split off __bdi_set_max_ratio() function mm: add bdi_set_max_bytes() function. mm: Add new knob /sys/class/bdi//max_bytes mm: document new /sys/class/bdi//max_bytes knob mm: add bdi_get_min_bytes() function. mm: split off __bdi_set_min_ratio() function mm: add bdi_set_min_bytes() function mm: add new /sys/class/bdi//min_bytes knob mm: document new /sys/class/bdi//min_bytes knob Documentation/ABI/testing/sysfs-class-bdi | 40 +++++++ include/linux/backing-dev.h | 8 ++ mm/backing-dev.c | 93 +++++++++++++++- mm/page-writeback.c | 126 ++++++++++++++++++++-- 4 files changed, 253 insertions(+), 14 deletions(-) base-commit: e2302539dd4f1c62d96651c07ddb05aa2461d29c --=20 2.30.2