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Qu Wenruo 1db7959aac btrfs: do not wait for short bulk allocation 
[BUG]
There is a recent report that when memory pressure is high (including
cached pages), btrfs can spend most of its time on memory allocation in
btrfs_alloc_page_array() for compressed read/write.

[CAUSE]
For btrfs_alloc_page_array() we always go alloc_pages_bulk_array(), and
even if the bulk allocation failed (fell back to single page
allocation) we still retry but with extra memalloc_retry_wait().

If the bulk alloc only returned one page a time, we would spend a lot of
time on the retry wait.

The behavior was introduced in commit 395cb57e85 ("btrfs: wait between
incomplete batch memory allocations").

[FIX]
Although the commit mentioned that other filesystems do the wait, it's
not the case at least nowadays.

All the mainlined filesystems only call memalloc_retry_wait() if they
failed to allocate any page (not only for bulk allocation).
If there is any progress, they won't call memalloc_retry_wait() at all.

For example, xfs_buf_alloc_pages() would only call memalloc_retry_wait()
if there is no allocation progress at all, and the call is not for
metadata readahead.

So I don't believe we should call memalloc_retry_wait() unconditionally
for short allocation.

Call memalloc_retry_wait() if it fails to allocate any page for tree
block allocation (which goes with __GFP_NOFAIL and may not need the
special handling anyway), and reduce the latency for
btrfs_alloc_page_array().

Reported-by: Julian Taylor <julian.taylor@1und1.de>
Tested-by: Julian Taylor <julian.taylor@1und1.de>
Link: https://lore.kernel.org/all/8966c095-cbe7-4d22-9784-a647d1bf27c3@1und1.de/
Fixes: 395cb57e85 ("btrfs: wait between incomplete batch memory allocations")
CC: stable@vger.kernel.org # 6.1+
Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
 		2024-04-09 23:20:32 +02:00
Documentation Including fixes from bluetooth, WiFi and netfilter. 2024-02-29 12:40:20 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
arch powerpc fixes for 6.8 #5 2024-03-03 09:47:19 -08:00
block block: sed-opal: handle empty atoms when parsing response 2024-02-16 15:52:45 -07:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto crypto: lskcipher - Copy IV in lskcipher glue code always 2024-02-24 08:37:24 +08:00
drivers phy second set of fixes for 6.8 2024-03-03 09:56:49 -08:00
fs btrfs: do not wait for short bulk allocation 2024-04-09 23:20:32 +02:00
include btrfs: qgroup: validate btrfs_qgroup_inherit parameter 2024-03-05 17:13:24 +01:00
init update workarounds for gcc "asm goto" issue 2024-02-15 11:14:33 -08:00
io_uring io_uring/net: fix multishot accept overflow handling 2024-02-14 18:30:19 -07:00
ipc shm: Slim down dependencies 2023-12-20 19:26:31 -05:00
kernel Probes fixes for v6.8-rc5: 2024-03-01 11:17:23 -08:00
lib Including fixes from bluetooth, WiFi and netfilter. 2024-02-29 12:40:20 -08:00
mm 6 hotfixes. 3 are cc:stable and the remainder address post-6.7 issues 2024-02-27 16:44:15 -08:00
net bluetooth pull request for net: 2024-02-29 09:10:24 -08:00
rust Rust changes for v6.8 2024-01-11 13:05:41 -08:00
samples work around gcc bugs with 'asm goto' with outputs 2024-02-09 15:57:48 -08:00
scripts RISC-V Fixes for 6.8-rc7 2024-03-01 12:44:33 -08:00
security tomoyo: fix UAF write bug in tomoyo_write_control() 2024-03-01 11:14:00 -08:00
sound ASoC: Fixes for v6.8 2024-02-29 08:29:04 +01:00
tools powerpc fixes for 6.8 #5 2024-03-03 09:47:19 -08:00
usr Kbuild updates for v6.8 2024-01-18 17:57:07 -08:00
virt Generic: 2024-01-17 13:03:37 -08:00
.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 get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore Add .editorconfig file for basic formatting 2023-12-28 16:22:47 +09:00
.mailmap MAINTAINERS: mailmap: update Shakeel's email address 2024-02-20 14:20:50 -08:00
.rustfmt.toml rust: add `.rustfmt.toml` 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: supplement of zswap maintainers update 2024-01-25 23:52:21 -08:00
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 RISC-V Fixes for 6.8-rc7 2024-03-01 12:44:33 -08:00
Makefile Linux 6.8-rc7 2024-03-03 13:02:52 -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.