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Jan Kara 162bc7bd73 bfq: Do not let waker requests skip proper accounting [ Upstream commit `c65e6fd460` ] Commit `7cc4ffc555` ("block, bfq: put reqs of waker and woken in dispatch list") added a condition to bfq_insert_request() which added waker's requests directly to dispatch list. The rationale was that completing waker's IO is needed to get more IO for the current queue. Although this rationale is valid, there is a hole in it. The waker does not necessarily serve the IO only for the current queue and maybe it's current IO is not needed for current queue to make progress. Furthermore injecting IO like this completely bypasses any service accounting within bfq and thus we do not properly track how much service is waker's queue getting or that the waker is actually doing any IO. Depending on the conditions this can result in the waker getting too much or too few service. Consider for example the following job file: [global] directory=/mnt/repro/ rw=write size=8g time_based runtime=30 ramp_time=10 blocksize=1m direct=0 ioengine=sync [slowwriter] numjobs=1 prioclass=2 prio=7 fsync=200 [fastwriter] numjobs=1 prioclass=2 prio=0 fsync=200 Despite processes have very different IO priorities, they get the same about of service. The reason is that bfq identifies these processes as having waker-wakee relationship and once that happens, IO from fastwriter gets injected during slowwriter's time slice. As a result bfq is not aware that fastwriter has any IO to do and constantly schedules only slowwriter's queue. Thus fastwriter is forced to compete with slowwriter's IO all the time instead of getting its share of time based on IO priority. Drop the special injection condition from bfq_insert_request(). As a result, requests will be tracked and queued in a normal way and on next dispatch bfq_select_queue() can decide whether the waker's inserted requests should be injected during the current queue's timeslice or not. Fixes: `7cc4ffc555` ("block, bfq: put reqs of waker and woken in dispatch list") Acked-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jan Kara <jack@suse.cz> Link: https://lore.kernel.org/r/20211125133645.27483-8-jack@suse.cz Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org>		2022-01-27 11:03:18 +01:00
arch	arm64: dts: ti: k3-j721e: correct cache-sets info	2022-01-27 11:03:17 +01:00
block	bfq: Do not let waker requests skip proper accounting	2022-01-27 11:03:18 +01:00
certs	certs: Add support for using elliptic curve keys for signing modules	2021-08-23 19:55:42 +03:00
crypto	crypto: pcrypt - Delay write to padata->info	2021-11-18 19:16:44 +01:00
Documentation	Input: i8042 - add deferred probe support	2022-01-05 12:42:32 +01:00
drivers	mfd: atmel-flexcom: Use .resume_noirq	2022-01-27 11:03:18 +01:00
fs	fs: dlm: fix build with CONFIG_IPV6 disabled	2022-01-27 11:03:13 +01:00
include	mm_zone: add function to check if managed dma zone exists	2022-01-27 11:03:00 +01:00
init	init: make unknown command line param message clearer	2021-11-18 19:17:11 +01:00
ipc	shm: extend forced shm destroy to support objects from several IPC nses	2021-11-25 09:48:42 +01:00
kernel	dma/pool: create dma atomic pool only if dma zone has managed pages	2022-01-27 11:03:00 +01:00
lib	siphash: use _unaligned version by default	2021-12-08 09:04:47 +01:00
LICENSES	LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes"	2021-07-15 06:31:24 -06:00
mm	shmem: fix a race between shmem_unused_huge_shrink and shmem_evict_inode	2022-01-27 11:03:01 +01:00
net	Bluetooth: stop proccessing malicious adv data	2022-01-27 11:03:11 +01:00
samples	ftrace/samples: Add missing prototypes direct functions	2022-01-11 15:35:13 +01:00
scripts	recordmcount.pl: fix typo in s390 mcount regex	2022-01-05 12:42:33 +01:00
security	selinux: initialize proto variable in selinux_ip_postroute_compat()	2022-01-05 12:42:34 +01:00
sound	ALSA: core: Fix SSID quirk lookup for subvendor=0	2022-01-27 11:02:47 +01:00
tools	libbpf: Fix using invalidated memory in bpf_linker	2022-01-27 11:03:16 +01:00
usr	.gitignore: prefix local generated files with a slash	2021-05-02 00:43:35 +09:00
virt	KVM: downgrade two BUG_ONs to WARN_ON_ONCE	2021-12-22 09:32:34 +01:00
.clang-format	clang-format: Update with the latest for_each macro list	2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore	Opt out of scripts/get_maintainer.pl	2019-05-16 10:53:40 -07:00
.gitattributes	.gitattributes: use 'dts' diff driver for dts files	2019-12-04 19:44:11 -08:00
.gitignore	.gitignore: ignore only top-level modules.builtin	2021-05-02 00:43:35 +09:00
.mailmap	mailmap: add Andrej Shadura	2021-10-18 20:22:03 -10:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Daniel Drake to credits	2021-09-21 08:34:58 +03:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	drm fixes for 5.15 final	2021-10-28 12:17:01 -07:00
Makefile	Linux 5.15.16	2022-01-20 09:13:16 +01:00
README	Drop all 00-INDEX files from Documentation/	2018-09-09 15:08:58 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.