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Jens Axboe 7b05bf7710 Revert "block/mq-deadline: Prioritize high-priority requests"
This reverts commit fb926032b3.

Zhen reports that this commit slows down mq-deadline on a 128 thread
box, going from 258K IOPS to 170-180K. My testing shows that Optane
gen2 IOPS goes from 2.3M IOPS to 1.2M IOPS on a 64 thread box.

Looking in detail at the code, the main culprit here is needing to sum
percpu counters in the dispatch hot path, leading to very high CPU
utilization there. To make matters worse, the code currently needs to
sum 2 percpu counters, and it does so in the most naive way of iterating
possible CPUs _twice_.

Since we're close to release, revert this commit and we can re-do it
with regular per-priority counters instead for the 5.15 kernel.

Link: https://lore.kernel.org/linux-block/20210826144039.2143-1-thunder.leizhen@huawei.com/
Reported-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-08-26 12:59:44 -06:00
arch ubd: remove dead code in ubd_setup_common 2021-06-30 15:35:45 -06:00
block Revert "block/mq-deadline: Prioritize high-priority requests" 2021-08-26 12:59:44 -06:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2021-06-28 16:04:56 -07:00
Documentation for-5.14/block-2021-06-29 2021-06-30 12:12:56 -07:00
drivers nbd: Aovid double completion of a request 2021-08-13 09:46:48 -06:00
fs block: delay freeing the gendisk 2021-07-27 19:35:47 -06:00
include block: increase BLKCG_MAX_POLS 2021-07-17 13:07:24 -06:00
init for-5.14/block-2021-06-29 2021-06-30 12:12:56 -07:00
ipc Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2021-06-28 20:39:26 -07:00
kernel for-5.14/block-2021-06-29 2021-06-30 12:12:56 -07:00
lib Merge branch 'akpm' (patches from Andrew) 2021-06-29 17:29:11 -07:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm for-5.14/block-2021-06-29 2021-06-30 12:12:56 -07:00
net Merge branch 'akpm' (patches from Andrew) 2021-06-29 17:29:11 -07:00
samples This was a reasonably active cycle for documentation; this pull includes: 2021-06-28 16:53:05 -07:00
scripts Merge branch 'akpm' (patches from Andrew) 2021-06-29 17:29:11 -07:00
security integrity-v5.14 2021-06-28 16:15:50 -07:00
sound spi: Updates for v5.14 2021-06-28 11:10:20 -07:00
tools platform-drivers-x86 for v5.14-1 2021-06-30 11:15:39 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt Merge branch 'akpm' (patches from Andrew) 2021-06-29 17:29:11 -07:00
.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 m68k updates for v5.14 2021-06-28 14:01:03 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
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 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid 2021-06-30 11:31:32 -07:00
Makefile arm64 updates for 5.14 2021-06-28 14:04:24 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.