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Paolo Valente bf2b79e7c4 block, bfq: boost the throughput on NCQ-capable flash-based devices
This patch boosts the throughput on NCQ-capable flash-based devices,
while still preserving latency guarantees for interactive and soft
real-time applications. The throughput is boosted by just not idling
the device when the in-service queue remains empty, even if the queue
is sync and has a non-null idle window. This helps to keep the drive's
internal queue full, which is necessary to achieve maximum
performance. This solution to boost the throughput is a port of
commits a68bbdd and f7d7b7a for CFQ.

As already highlighted in a previous patch, allowing the device to
prefetch and internally reorder requests trivially causes loss of
control on the request service order, and hence on service guarantees.
Fortunately, as discussed in detail in the comments on the function
bfq_bfqq_may_idle(), if every process has to receive the same
fraction of the throughput, then the service order enforced by the
internal scheduler of a flash-based device is relatively close to that
enforced by BFQ. In particular, it is close enough to let service
guarantees be substantially preserved.

Things change in an asymmetric scenario, i.e., if not every process
has to receive the same fraction of the throughput. In this case, to
guarantee the desired throughput distribution, the device must be
prevented from prefetching requests. This is exactly what this patch
does in asymmetric scenarios.

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2017-04-19 08:30:26 -06:00
arch Merge branch 'regset' (PTRACE_SETREGSET data leakage) 2017-03-29 08:55:25 -07:00
block block, bfq: boost the throughput on NCQ-capable flash-based devices 2017-04-19 08:30:26 -06:00
certs certs: Add a secondary system keyring that can be added to dynamically 2016-04-11 22:48:09 +01:00
crypto net: Work around lockdep limitation in sockets that use sockets 2017-03-09 18:23:27 -08:00
Documentation block, bfq: improve responsiveness 2017-04-19 08:30:26 -06:00
drivers nbd: set the max segment size to UINT_MAX 2017-04-19 08:16:06 -06:00
firmware WHENCE: use https://linuxtv.org for LinuxTV URLs 2015-12-04 10:35:11 -02:00
fs block_dev: use blkdev_issue_zerout for hole punches 2017-04-08 11:25:38 -06:00
include block, bfq: add full hierarchical scheduling and cgroups support 2017-04-19 08:30:26 -06:00
init Change get_random_{int,log} to use the CRNG used by /dev/urandom and 2017-03-11 09:08:47 -08:00
ipc Merge branch 'WIP.sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-03 10:16:38 -08:00
kernel Merge branch 'stable-4.11' of git://git.infradead.org/users/pcmoore/audit 2017-03-25 15:13:55 -07:00
lib sbitmap: add sbitmap_get_shallow() operation 2017-04-14 14:06:52 -06:00
mm Merge branch 'for-linus' into for-4.12/block 2017-04-07 12:45:20 -06:00
net net: off by one in inet6_pton() 2017-04-14 14:08:54 -06:00
samples Merge branch 'rebased-statx' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-03-03 11:38:56 -08:00
scripts Merge branch 'akpm' (patches from Andrew) 2017-03-10 08:34:42 -08:00
security Merge branch 'WIP.sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-03 10:16:38 -08:00
sound ALSA: hda - Adding a group of pin definition to fix headset problem 2017-03-23 09:39:55 +01:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-03-23 11:29:49 -07:00
usr kbuild: initramfs cleanup, set target from Kconfig 2017-01-05 09:40:16 -08:00
virt KVM: pci-assign: do not map smm memory slot pages in vt-d page tables 2017-03-28 10:08:54 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2016-08-02 16:48:52 -04:00
.mailmap mailmap: add codeaurora.org names for nameless email commits 2017-01-10 18:31:55 -08:00
COPYING
CREDITS MAINTAINERS: Remove old e-mail address 2017-02-13 12:24:56 -05:00
Kbuild scripts/gdb: provide linux constants 2016-05-23 17:04:14 -07:00
Kconfig
MAINTAINERS A new EDAC driver for the Pondicherry2 memory controller IP found in the 2017-03-27 11:09:00 -07:00
Makefile Linux 4.11-rc4 2017-03-26 14:15:16 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.