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Tejun Heo 4cddeacad6 Revert "block: inherit request start time from bio for BLK_CGROUP" 
This reverts commit 0006707723. It has a
couple problems:

* bio_issue_time() is stored in bio->bi_issue truncated to 51 bits. This
  overflows in slightly over 26 days. Setting rq->io_start_time_ns with it
  means that io duration calculation would yield >26days after 26 days of
  uptime. This, for example, confuses kyber making it cause high IO
  latencies.

* rq->io_start_time_ns should record the time that the IO is issued to the
  device so that on-device latency can be measured. However,
  bio_issue_time() is set before the bio goes through the rq-qos controllers
  (wbt, iolatency, iocost), so when the bio gets throttled in any of the
  mechanisms, the measured latencies make no sense - on-device latencies end
  up higher than request-alloc-to-completion latencies.

We'll need a smarter way to avoid calling ktime_get_ns() repeatedly
back-to-back. For now, let's revert the commit.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # v5.16+
Link: https://lore.kernel.org/r/YmmeOLfo5lzc+8yI@slm.duckdns.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
History 2022-04-27 13:51:28 -06:00
arch A set of x86 fixes and updates: 2022-04-03 12:15:47 -07:00
block Revert "block: inherit request start time from bio for BLK_CGROUP" 2022-04-27 13:51:28 -06:00
certs Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
crypto for-5.18/64bit-pi-2022-03-25 2022-03-26 12:01:35 -07:00
Documentation Updates to Tracing: 2022-04-03 12:26:01 -07:00
drivers bcache: fix wrong bdev parameter when calling bio_alloc_clone() in do_bio_hook() 2022-04-19 11:28:17 -06:00
fs Updates to Tracing: 2022-04-03 12:26:01 -07:00
include asm-generic: fix __get_unaligned_be48() on 32 bit platforms 2022-04-12 16:31:38 -06:00
init Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
ipc fs: allocate inode by using alloc_inode_sb() 2022-03-22 15:57:03 -07:00
kernel Updates to Tracing: 2022-04-03 12:26:01 -07:00
lib for-5.18/block-2022-04-01 2022-04-01 16:20:00 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm Filesystem/VFS changes for 5.18, part two 2022-04-01 13:50:50 -07:00
net Networking fixes for 5.18-rc1 and rethook patches. 2022-03-31 11:23:31 -07:00
samples dma-mapping updates for Linux 5.18 2022-03-29 08:50:14 -07:00
scripts modpost: restore the warning message for missing symbol versions 2022-04-03 03:11:51 +09:00
security hardening updates for v5.18-rc1-fix1 2022-03-31 11:43:01 -07:00
sound sound fixes for 5.18-rc1 2022-04-01 10:32:46 -07:00
tools A set of x86 fixes and updates: 2022-04-03 12:15:47 -07:00
usr Kbuild updates for v5.18 2022-03-31 11:59:03 -07:00
virt KVM: Remove dirty handling from gfn_to_pfn_cache completely 2022-04-02 05:34:41 -04:00
.clang-format genirq/msi: Make interrupt allocation less convoluted 2021-12-16 22:22:20 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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: update Kirill's email 2022-04-01 11:46:09 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: replace a Microchip AT91 maintainer 2022-02-09 11:30:01 +01:00
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 chrome platform changes for 5.18 2022-04-02 10:44:18 -07:00
Makefile Linux 5.18-rc1 2022-04-03 14:08:21 -07:00
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.