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David S. Miller 44b9b6ca25 Merge branch 'net-sched-move-back-qlen-to-per-CPU-accounting'
Paolo Abeni says:

====================
net: sched: move back qlen to per CPU accounting

The commit 46b1c18f9d ("net: sched: put back q.qlen into a single location")
introduced some measurable regression in the contended scenarios for
lock qdisc.

As Eric suggested we could replace q.qlen access with calls to qdisc_is_empty()
in the datapath and revert the above commit. The TC subsystem updates
qdisc->is_empty in a somewhat loose way: notably 'is_empty' is set only when
the qdisc dequeue() calls return a NULL ptr. That is, the invocation after
the last packet is dequeued.

The above is good enough for BYPASS implementation - the only downside is that
we end up avoiding the optimization for a very small time-frame - but will
break hard things when internal structures consistency for classful qdisc
relies on child qdisc_is_empty().

A more strict 'is_empty' update adds a relevant complexity to its life-cycle, so
this series takes a different approach: we allow lockless qdisc to switch from
per CPU accounting to global stats accounting when the NOLOCK bit is cleared.
Since most pieces of infrastructure are already in place, this requires very
little changes to the pfifo_fast qdisc, and any later NOLOCK qdisc can hook
there with little effort - no need to maintain two different implementations.

The first 2 patches removes direct qlen access from non core TC code, the 3rd
and 4th patches place and use the infrastructure to allow stats account
switching and the 5th patch is the actual revert.

 v1 -> v2:
  - fixed build issues
  - more descriptive commit message for patch 5/5
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
2019-04-10 12:20:46 -07:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-08 23:39:36 -07:00
LICENSES LICENSES: Add GCC runtime library exception text 2019-01-16 14:54:15 -07:00
arch xtensa fixes for v5.1-rc5 2019-04-08 17:04:42 -10:00
block block: Revert v5.0 blk_mq_request_issue_directly() changes 2019-04-05 09:40:46 -06:00
certs kexec, KEYS: Make use of platform keyring for signature verify 2019-02-04 17:34:07 -05:00
crypto lib/lzo: separate lzo-rle from lzo 2019-03-07 18:32:03 -08:00
drivers net: phy: remove unnecessary callback settings in C45 drivers 2019-04-09 13:07:07 -07:00
fs for-linus-20190407 2019-04-07 13:28:36 -10:00
include Revert: "net: sched: put back q.qlen into a single location" 2019-04-10 12:20:46 -07:00
init init/main: add checks for the return value of memblock_alloc*() 2019-03-12 10:04:02 -07:00
ipc rhashtable: use bit_spin_locks to protect hash bucket. 2019-04-07 19:12:12 -07:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-08 23:39:36 -07:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-08 23:39:36 -07:00
mm slab: fix a crash by reading /proc/slab_allocators 2019-04-07 19:23:12 -10:00
net Revert: "net: sched: put back q.qlen into a single location" 2019-04-10 12:20:46 -07:00
samples samples: bpf: add xdp_sample_pkts to .gitignore 2019-03-21 19:35:36 -07:00
scripts fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock 2019-04-06 07:01:55 -10:00
security KEYS: trusted: fix -Wvarags warning 2019-04-08 15:58:54 -07:00
sound sound fixes for 5.1-rc3 2019-03-29 14:53:33 -07:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-08 23:39:36 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt KVM/ARM fixes for 5.1 2019-03-28 19:07:30 +01:00
.clang-format rhashtable: rename rht_for_each*continue as *from. 2019-03-21 14:01:10 -07:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap Update Nicolas Pitre's email address 2019-04-02 18:12:44 -10:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-08 23:39:36 -07:00
Makefile Linux 5.1-rc4 2019-04-07 14:09:59 -10:00
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.