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Brian Vazquez 492e0d0d6f bpf: Do not grab the bucket spinlock by default on htab batch ops
Grabbing the spinlock for every bucket even if it's empty, was causing
significant perfomance cost when traversing htab maps that have only a
few entries. This patch addresses the issue by checking first the
bucket_cnt, if the bucket has some entries then we go and grab the
spinlock and proceed with the batching.

Tested with a htab of size 50K and different value of populated entries.

Before:
  Benchmark             Time(ns)        CPU(ns)
  ---------------------------------------------
  BM_DumpHashMap/1       2759655        2752033
  BM_DumpHashMap/10      2933722        2930825
  BM_DumpHashMap/200     3171680        3170265
  BM_DumpHashMap/500     3639607        3635511
  BM_DumpHashMap/1000    4369008        4364981
  BM_DumpHashMap/5k     11171919       11134028
  BM_DumpHashMap/20k    69150080       69033496
  BM_DumpHashMap/39k   190501036      190226162

After:
  Benchmark             Time(ns)        CPU(ns)
  ---------------------------------------------
  BM_DumpHashMap/1        202707         200109
  BM_DumpHashMap/10       213441         210569
  BM_DumpHashMap/200      478641         472350
  BM_DumpHashMap/500      980061         967102
  BM_DumpHashMap/1000    1863835        1839575
  BM_DumpHashMap/5k      8961836        8902540
  BM_DumpHashMap/20k    69761497       69322756
  BM_DumpHashMap/39k   187437830      186551111

Fixes: 057996380a ("bpf: Add batch ops to all htab bpf map")
Signed-off-by: Brian Vazquez <brianvv@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200218172552.215077-1-brianvv@google.com
2020-02-19 15:59:30 -08:00
Documentation ARM: SoC-related driver updates 2020-02-08 14:04:19 -08:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch powerpc fixes for 5.6 #2 2020-02-08 14:28:26 -08:00
block block-5.6-2020-02-05 2020-02-06 06:15:23 +00:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto treewide: remove redundant IS_ERR() before error code check 2020-02-04 03:05:27 +00:00
drivers qmi_wwan: unconditionally reject 2 ep interfaces 2020-02-10 14:03:27 +01:00
fs compat-ioctl fix for v5.6 2020-02-08 13:44:41 -08:00
include bpf, uapi: Remove text about bpf_redirect_map() giving higher performance 2020-02-18 15:31:31 +01:00
init Tracing updates: 2020-02-06 07:12:11 +00:00
ipc proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
kernel bpf: Do not grab the bucket spinlock by default on htab batch ops 2020-02-19 15:59:30 -08:00
lib Tracing updates: 2020-02-06 07:12:11 +00:00
mm Merge branch 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-02-08 13:26:41 -08:00
net xsk: Publish global consumer pointers when NAPI is finished 2020-02-11 15:51:11 +01:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf 2020-02-08 15:01:03 +01:00
scripts A handful of small documentation fixes that wandered in. 2020-02-07 13:03:10 -08:00
security Merge branch 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-02-08 13:26:41 -08:00
sound sound fixes for 5.6-rc1 2020-02-06 14:15:01 +00:00
tools libbpf: Sanitise internal map names so they are not rejected by the kernel 2020-02-18 15:34:20 +01:00
usr initramfs: do not show compression mode choice if INITRAMFS_SOURCE is empty 2020-02-03 17:31:43 +00:00
virt KVM: fix overflow of zero page refcount with ksm running 2020-02-05 15:27:46 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.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 modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
.mailmap A handful of small documentation fixes that wandered in. 2020-02-07 13:03:10 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS open: introduce openat2(2) syscall 2020-01-18 09:19:18 -05:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS SCSI misc on 20200208 2020-02-08 17:24:41 -08:00
Makefile Kbuild updates for v5.6 2020-02-01 10:01:52 -08:00
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.