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7fd3253a7d
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Björn Töpel 7fd3253a7d net: Introduce preferred busy-polling 
The existing busy-polling mode, enabled by the SO_BUSY_POLL socket
option or system-wide using the /proc/sys/net/core/busy_read knob, is
an opportunistic. That means that if the NAPI context is not
scheduled, it will poll it. If, after busy-polling, the budget is
exceeded the busy-polling logic will schedule the NAPI onto the
regular softirq handling.

One implication of the behavior above is that a busy/heavy loaded NAPI
context will never enter/allow for busy-polling. Some applications
prefer that most NAPI processing would be done by busy-polling.

This series adds a new socket option, SO_PREFER_BUSY_POLL, that works
in concert with the napi_defer_hard_irqs and gro_flush_timeout
knobs. The napi_defer_hard_irqs and gro_flush_timeout knobs were
introduced in commit 6f8b12d661 ("net: napi: add hard irqs deferral
feature"), and allows for a user to defer interrupts to be enabled and
instead schedule the NAPI context from a watchdog timer. When a user
enables the SO_PREFER_BUSY_POLL, again with the other knobs enabled,
and the NAPI context is being processed by a softirq, the softirq NAPI
processing will exit early to allow the busy-polling to be performed.

If the application stops performing busy-polling via a system call,
the watchdog timer defined by gro_flush_timeout will timeout, and
regular softirq handling will resume.

In summary; Heavy traffic applications that prefer busy-polling over
softirq processing should use this option.

Example usage:

  $ echo 2 | sudo tee /sys/class/net/ens785f1/napi_defer_hard_irqs
  $ echo 200000 | sudo tee /sys/class/net/ens785f1/gro_flush_timeout

Note that the timeout should be larger than the userspace processing
window, otherwise the watchdog will timeout and fall back to regular
softirq processing.

Enable the SO_BUSY_POLL/SO_PREFER_BUSY_POLL options on your socket.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/bpf/20201130185205.196029-2-bjorn.topel@gmail.com
2020-12-01 00:09:25 +01:00
arch net: Introduce preferred busy-polling 2020-12-01 00:09:25 +01:00
block blk-mq: mark flush request as IDLE in flush_end_io() 2020-10-30 08:33:49 -06:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto drivers-5.10-2020-10-12 2020-10-13 13:04:41 -07:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2020-11-14 09:13:41 -08:00
drivers i40e: Use batched xsk Tx interfaces to increase performance 2020-11-17 22:07:40 +01:00
fs net: Introduce preferred busy-polling 2020-12-01 00:09:25 +01:00
include net: Introduce preferred busy-polling 2020-12-01 00:09:25 +01:00
init linux-kselftest-kunit-5.10-rc1 2020-10-18 14:45:59 -07:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel bpf: Add a BPF helper for getting the IMA hash of an inode 2020-11-26 00:04:04 +01:00
lib Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2020-11-14 09:13:41 -08:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm/truncate.c: make __invalidate_mapping_pages() static 2020-11-02 12:14:19 -08:00
net net: Introduce preferred busy-polling 2020-12-01 00:09:25 +01:00
samples samples: bpf: Remove bpf_load loader completely 2020-11-26 19:33:36 -08:00
scripts bpf: Add a BPF helper for getting the IMA hash of an inode 2020-11-26 00:04:04 +01:00
security ima: Implement ima_inode_hash 2020-11-26 00:04:04 +01:00
sound ASoC: Fixes for v5.10 2020-11-05 18:19:32 +01:00
tools selftests/bpf: Fix flavored variants of test_ima 2020-11-30 22:56:32 +01:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt kvm: x86/mmu: Support dirty logging for the TDP MMU 2020-10-23 03:42:13 -04:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap MAINTAINERS: jarkko.sakkinen@linux.intel.com -> jarkko@kernel.org 2020-10-16 11:11:19 -07:00
COPYING
CREDITS MAINTAINERS: Move Sangbeom Kim to credits 2020-10-26 10:11:18 +01:00
Kbuild
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-11-12 16:54:48 -08:00
Makefile Linux 5.10-rc3 2020-11-08 16:10:16 -08:00
README

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.