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Andrii Nakryiko cdf355cc60 uprobes: add speculative lockless system-wide uprobe filter check
It's very common with BPF-based uprobe/uretprobe use cases to have
a system-wide (not PID specific) probes used. In this case uprobe's
trace_uprobe_filter->nr_systemwide counter is bumped at registration
time, and actual filtering is short circuited at the time when
uprobe/uretprobe is triggered.

This is a great optimization, and the only issue with it is that to even
get to checking this counter uprobe subsystem is taking
read-side trace_uprobe_filter->rwlock. This is actually noticeable in
profiles and is just another point of contention when uprobe is
triggered on multiple CPUs simultaneously.

This patch moves this nr_systemwide check outside of filter list's
rwlock scope, as rwlock is meant to protect list modification, while
nr_systemwide-based check is speculative and racy already, despite the
lock (as discussed in [0]). trace_uprobe_filter_remove() and
trace_uprobe_filter_add() already check for filter->nr_systewide
explicitly outside of __uprobe_perf_filter, so no modifications are
required there.

Confirming with BPF selftests's based benchmarks.

BEFORE (based on changes in previous patch)
===========================================
uprobe-nop     :    2.732 ± 0.022M/s
uprobe-push    :    2.621 ± 0.016M/s
uprobe-ret     :    1.105 ± 0.007M/s
uretprobe-nop  :    1.396 ± 0.007M/s
uretprobe-push :    1.347 ± 0.008M/s
uretprobe-ret  :    0.800 ± 0.006M/s

AFTER
=====
uprobe-nop     :    2.878 ± 0.017M/s (+5.5%, total +8.3%)
uprobe-push    :    2.753 ± 0.013M/s (+5.3%, total +10.2%)
uprobe-ret     :    1.142 ± 0.010M/s (+3.8%, total +3.8%)
uretprobe-nop  :    1.444 ± 0.008M/s (+3.5%, total +6.5%)
uretprobe-push :    1.410 ± 0.010M/s (+4.8%, total +7.1%)
uretprobe-ret  :    0.816 ± 0.002M/s (+2.0%, total +3.9%)

In the above, first percentage value is based on top of previous patch
(lazy uprobe buffer optimization), while the "total" percentage is
based on kernel without any of the changes in this patch set.

As can be seen, we get about 4% - 10% speed up, in total, with both lazy
uprobe buffer and speculative filter check optimizations.

  [0] https://lore.kernel.org/bpf/20240313131926.GA19986@redhat.com/

Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/all/20240318181728.2795838-4-andrii@kernel.org/

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
2024-05-01 23:18:46 +09:00
arch Misc fixes: 2024-04-28 11:58:16 -07:00
block vfs-6.9-rc6.fixes 2024-04-26 11:01:28 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto This push fixes a regression that broke iwd as well as a divide by 2024-03-25 10:48:23 -07:00
Documentation Misc fixes: 2024-04-28 12:11:26 -07:00
drivers Fix a double free bug in the init error path of the 2024-04-28 11:51:13 -07:00
fs three smb3 client fixes, all also for stable 2024-04-27 11:35:40 -07:00
include Misc fixes: 2024-04-28 11:58:16 -07:00
init Rust fixes for v6.9 2024-04-27 12:11:55 -07:00
io_uring io_uring/net: restore msg_control on sendzc retry 2024-04-08 21:48:41 -06:00
ipc sysctl changes for v6.9-rc1 2024-03-18 14:59:13 -07:00
kernel uprobes: add speculative lockless system-wide uprobe filter check 2024-05-01 23:18:46 +09:00
lib 11 hotfixes. 8 are cc:stable and the remaining 3 (nice ratio!) address 2024-04-26 13:48:03 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm/hugetlb: fix DEBUG_LOCKS_WARN_ON(1) when dissolve_free_hugetlb_folio() 2024-04-25 10:07:27 -07:00
net Including fixes from netfilter, wireless and bluetooth. 2024-04-25 11:19:38 -07:00
rust rust: remove params from module macro example 2024-04-25 17:34:33 +02:00
samples Tracing updates for 6.9: 2024-03-18 15:11:44 -07:00
scripts Rust fixes for v6.9 2024-04-27 12:11:55 -07:00
security security: Place security_path_post_mknod() where the original IMA call was 2024-04-03 10:21:32 -07:00
sound ALSA: seq: ump: Fix conversion from MIDI2 to MIDI1 UMP messages 2024-04-19 12:07:14 +02:00
tools RISC-V Fixes for 6.9-rc6 2024-04-27 12:02:55 -07:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt KVM: Drop unused @may_block param from gfn_to_pfn_cache_invalidate_start() 2024-04-11 12:58:53 -07:00
.clang-format clang-format: Update with v6.7-rc4's for_each macro list 2023-12-08 23:54:38 +01:00
.cocciconfig
.editorconfig Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: create a list of all built DTB files 2024-02-19 18:20:39 +09:00
.mailmap Including fixes from netfilter, wireless and bluetooth. 2024-04-25 11:19:38 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING
CREDITS MAINTAINERS: Drop Gustavo Pimentel as PCI DWC Maintainer 2024-03-27 13:41:02 -05:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Fix a race condition in the at24 eeprom handler, a NULL pointer 2024-04-27 11:24:53 -07:00
Makefile Linux 6.9-rc6 2024-04-28 13:47:24 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.