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Filipe Manana 8773816459 btrfs: skip unnecessary searches for xattrs when logging an inode [ Upstream commit `f2f121ab50` ] Every time we log an inode we lookup in the fs/subvol tree for xattrs and if we have any, log them into the log tree. However it is very common to have inodes without any xattrs, so doing the search wastes times, but more importantly it adds contention on the fs/subvol tree locks, either making the logging code block and wait for tree locks or making the logging code making other concurrent operations block and wait. The most typical use cases where xattrs are used are when capabilities or ACLs are defined for an inode, or when SELinux is enabled. This change makes the logging code detect when an inode does not have xattrs and skip the xattrs search the next time the inode is logged, unless the inode is evicted and loaded again or a xattr is added to the inode. Therefore skipping the search for xattrs on inodes that don't ever have xattrs and are fsynced with some frequency. The following script that calls dbench was used to measure the impact of this change on a VM with 8 CPUs, 16Gb of ram, using a raw NVMe device directly (no intermediary filesystem on the host) and using a non-debug kernel (default configuration on Debian distributions): $ cat test.sh #!/bin/bash DEV=/dev/sdk MNT=/mnt/sdk MOUNT_OPTIONS="-o ssd" mkfs.btrfs -f -m single -d single $DEV mount $MOUNT_OPTIONS $DEV $MNT dbench -D $MNT -t 200 40 umount $MNT The results before this change: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 5761605 0.172 312.057 Close 4232452 0.002 10.927 Rename 243937 1.406 277.344 Unlink 1163456 0.631 298.402 Deltree 160 11.581 221.107 Mkdir 80 0.003 0.005 Qpathinfo 5221410 0.065 122.309 Qfileinfo 915432 0.001 3.333 Qfsinfo 957555 0.003 3.992 Sfileinfo 469244 0.023 20.494 Find 2018865 0.448 123.659 WriteX 2874851 0.049 118.529 ReadX 9030579 0.004 21.654 LockX 18754 0.003 4.423 UnlockX 18754 0.002 0.331 Flush 403792 10.944 359.494 Throughput 908.444 MB/sec 40 clients 40 procs max_latency=359.500 ms The results after this change: Operation Count AvgLat MaxLat ---------------------------------------- NTCreateX 6442521 0.159 230.693 Close 4732357 0.002 10.972 Rename 272809 1.293 227.398 Unlink 1301059 0.563 218.500 Deltree 160 7.796 54.887 Mkdir 80 0.008 0.478 Qpathinfo 5839452 0.047 124.330 Qfileinfo 1023199 0.001 4.996 Qfsinfo 1070760 0.003 5.709 Sfileinfo 524790 0.033 21.765 Find 2257658 0.314 125.611 WriteX 3211520 0.040 232.135 ReadX 10098969 0.004 25.340 LockX 20974 0.003 1.569 UnlockX 20974 0.002 3.475 Flush 451553 10.287 331.037 Throughput 1011.77 MB/sec 40 clients 40 procs max_latency=331.045 ms +10.8% throughput, -8.2% max latency Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> Signed-off-by: Sasha Levin <sashal@kernel.org>		2021-01-17 14:16:53 +01:00
arch	powerpc/32s: Fix RTAS machine check with VMAP stack	2021-01-17 14:16:52 +01:00
block	blk-iocost: fix NULL iocg deref from racing against initialization	2021-01-12 20:18:23 +01:00
certs	.gitignore: add SPDX License Identifier	2020-03-25 11:50:48 +01:00
crypto	crypto: asym_tpm: correct zero out potential secrets	2021-01-12 20:18:17 +01:00
Documentation	dt-bindings: rtc: add reset-source property	2021-01-09 13:46:22 +01:00
drivers	scsi: ufs: Fix -Wsometimes-uninitialized warning	2021-01-17 14:16:53 +01:00
fs	btrfs: skip unnecessary searches for xattrs when logging an inode	2021-01-17 14:16:53 +01:00
include	bcache: introduce BCH_FEATURE_INCOMPAT_LOG_LARGE_BUCKET_SIZE for large bucket	2021-01-12 20:18:25 +01:00
init	exec: Transform exec_update_mutex into a rw_semaphore	2021-01-09 13:46:24 +01:00
ipc	ipc: adjust proc_ipc_sem_dointvec definition to match prototype	2020-09-05 12:14:29 -07:00
kernel	workqueue: Kick a worker based on the actual activation of delayed works	2021-01-12 20:18:14 +01:00
lib	lib/genalloc: fix the overflow when size is too big	2021-01-12 20:18:16 +01:00
LICENSES	LICENSES/deprecated: add Zlib license text	2020-09-16 14:33:49 +02:00
mm	mm: make wait_on_page_writeback() wait for multiple pending writebacks	2021-01-12 20:18:22 +01:00
net	xsk: Fix memory leak for failed bind	2021-01-12 20:18:26 +01:00
samples	samples/bpf: Fix possible hang in xdpsock with multiple threads	2020-12-30 11:53:49 +01:00
scripts	depmod: handle the case of /sbin/depmod without /sbin in PATH	2021-01-12 20:18:16 +01:00
security	ima: Don't modify file descriptor mode on the fly	2020-12-30 11:54:17 +01:00
sound	ALSA: hda/realtek: Add two "Intel Reference board" SSID in the ALC256.	2021-01-12 20:18:24 +01:00
tools	selftests/vm: fix building protection keys test	2021-01-12 20:18:14 +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: check tlbs_dirty directly	2021-01-12 20:18:22 +01:00
.clang-format	RDMA 5.10 pull request	2020-10-17 11:18:18 -07:00
.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	.gitignore: docs: ignore sphinx_*/ directories	2020-09-10 10:44:31 -06:00
.mailmap	mailmap: add two more addresses of Uwe Kleine-König	2020-12-06 10:19:07 -08:00
COPYING	COPYING: state that all contributions really are covered by this file	2020-02-10 13:32:20 -08:00
CREDITS	MAINTAINERS: Move Jason Cooper to CREDITS	2020-11-30 10:20:34 +01:00
Kbuild	kbuild: rename hostprogs-y/always to hostprogs/always-y	2020-02-04 01:53:07 +09:00
Kconfig	kbuild: ensure full rebuild when the compiler is updated	2020-05-12 13:28:33 +09:00
MAINTAINERS	Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net	2020-12-10 15:30:13 -08:00
Makefile	Linux 5.10.7	2021-01-12 20:18:27 +01:00
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.