From patchwork Mon Oct 24 19:05:49 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Roesch X-Patchwork-Id: 13018152 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 8F461C67871 for ; Mon, 24 Oct 2022 21:02:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233095AbiJXVCE (ORCPT ); Mon, 24 Oct 2022 17:02:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232746AbiJXVBj (ORCPT ); Mon, 24 Oct 2022 17:01:39 -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 75953160200 for ; Mon, 24 Oct 2022 12:07:12 -0700 (PDT) Received: by dev1180.prn1.facebook.com (Postfix, from userid 425415) id 447583ED5906; Mon, 24 Oct 2022 12:06:12 -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, willy@infradead.org, hch@infradead.org Subject: [RFC PATCH v3 00/14] mm/block: add bdi sysfs knobs Date: Mon, 24 Oct 2022 12:05:49 -0700 Message-Id: <20221024190603.3987969-1-shr@devkernel.io> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org At meta network block devices (nbd) are used to implement remote block storage. In testing and during production it has been observed that these network block devices can consume a huge portion of the dirty writeback cache and writeback can take a considerable time. To be able to give stricter limits, I'm proposing the following changes: 1) introduce 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 reached. 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) Use part of 1000 internal calculation The max_ratio is based on percentage. With the current machine sizes percentage values can be very high (1% of a 256GB main memory is already 2.5GB). This change uses part of 1000 instead of percentages for the internal calculations. 3) Introduce two new sysfs 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 bytes values, instead they will translate the byte value to a corresponding ratio. As the internal values are now part of 1000, the ratio is closer to the specified value. However the value should be more seen as an approximation as it can fluctuate over time. Changes: V3: - change signature of function bdi_ratio_from_pages to take an unsigned long parameter - use div64_u64 function for division to support 32 bit platforms - Refreshed to 6.1-rc2 V2: - Refreshed to 6.1-rc1 - Use part of 1000, instead of part of 10000 - Reformat cover letter *** BLURB HERE *** Stefan Roesch (14): mm: add bdi_set_strict_limit() function mm: add knob /sys/class/bdi//strict_limit mm: document /sys/class/bdi//strict_limit knob mm: use part per 1000 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 knob /sys/class/bdi//max_bytes mm: document /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 /sys/class/bdi//min_bytes knob mm: document /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 | 127 ++++++++++++++++++++-- 4 files changed, 254 insertions(+), 14 deletions(-) base-commit: 247f34f7b80357943234f93f247a1ae6b6c3a740