Commit Graph

5 Commits

Author SHA1 Message Date
Nick Terrell
2aa14b1ab2 zstd: import usptream v1.5.2
Updates the kernel's zstd library to v1.5.2, the latest zstd release.
The upstream tag it is updated to is `v1.5.2-kernel`, which contains
several cherry-picked commits on top of the v1.5.2 release which are
required for the kernel update. I will create this tag once the PR is
ready to merge, until then reference the temporary upstream branch
`v1.5.2-kernel-cherrypicks`.

I plan to submit this patch as part of the v6.2 merge window.

I've done basic build testing & testing on x86-64, i386, and aarch64.
I'm merging these patches into my `zstd-next` branch, which is pulled
into `linux-next` for further testing.

I've benchmarked BtrFS with zstd compression on a x86-64 machine, and
saw these results. Decompression speed is a small win across the board.
The lower compression levels 1-4 see both compression speed and
compression ratio wins. The higher compression levels see a small
compression speed loss and about neutral ratio. I expect the lower
compression levels to be used much more heavily than the high
compression levels, so this should be a net win.

Level	CTime	DTime	Ratio
1	-2.95%	-1.1%	-0.7%
3	-3.5%	-1.2%	-0.5%
5	+3.7%	-1.0%	+0.0%
7	+3.2%	-0.9%	+0.0%
9	-4.3%	-0.8%	+0.1%

Signed-off-by: Nick Terrell <terrelln@fb.com>
2022-10-24 12:12:32 -07:00
Nick Terrell
4782c725c1 zstd: Move zstd-common module exports to zstd_common_module.c
The zstd codebase is imported from the upstream zstd repo, and is over-written on
every update. Upstream keeps the kernel specific code separate from the main
library. So the module definition is moved into the zstd_common_module.c file.
This matches the pattern followed by the zstd-compress and zstd-decompress files.

I've done build and boot testing on x86-64, i386, and aarch64. I've
verified that zstd built both as modules and built-in build and boot.

Signed-off-by: Nick Terrell <terrelln@fb.com>
2022-10-24 12:12:26 -07:00
Alexey Kardashevskiy
637a642f5c zstd: Fixing mixed module-builtin objects
With CONFIG_ZSTD_COMPRESS=m and CONFIG_ZSTD_DECOMPRESS=y we end up in
a situation when files from lib/zstd/common/ are compiled once to be
linked later for ZSTD_DECOMPRESS (build-in) and ZSTD_COMPRESS (module)
even though CFLAGS are different for builtins and modules.
So far somehow this was not a problem but enabling LLVM LTO exposes
the problem as:

ld.lld: error: linking module flags 'Code Model': IDs have conflicting values in 'lib/built-in.a(zstd_common.o at 5868)' and 'ld-temp.o'

This particular conflict is caused by KBUILD_CFLAGS=-mcmodel=medium vs.
KBUILD_CFLAGS_MODULE=-mcmodel=large , modules use the large model on
POWERPC as explained at
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/Makefile?h=v5.18-rc4#n127
but the current use of common files is wrong anyway.

This works around the issue by introducing a zstd_common module with
shared code.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2022-10-03 03:52:58 +09:00
Nick Terrell
1974990cca lib: zstd: Don't inline functions in zstd_opt.c
`zstd_opt.c` contains the match finder for the highest compression
levels. These levels are already very slow, and are unlikely to be used
in the kernel. If they are used, they shouldn't be used in latency
sensitive workloads, so slowing them down shouldn't be a big deal.

This saves 188 KB of the 288 KB regression reported by Geert Uytterhoeven [0].
I've also opened an issue upstream [1] so that we can properly tackle
the code size issue in `zstd_opt.c` for all users, and can hopefully
remove this hack in the next zstd version we import.

Bloat-o-meter output on x86-64:

```
> ../scripts/bloat-o-meter vmlinux.old vmlinux
add/remove: 6/5 grow/shrink: 1/9 up/down: 16673/-209939 (-193266)
Function                                     old     new   delta
ZSTD_compressBlock_opt_generic.constprop       -    7559   +7559
ZSTD_insertBtAndGetAllMatches                  -    6304   +6304
ZSTD_insertBt1                                 -    1731   +1731
ZSTD_storeSeq                                  -     693    +693
ZSTD_BtGetAllMatches                           -     255    +255
ZSTD_updateRep                                 -     128    +128
ZSTD_updateTree                               96      99      +3
ZSTD_insertAndFindFirstIndexHash3             81       -     -81
ZSTD_setBasePrices.constprop                  98       -     -98
ZSTD_litLengthPrice.constprop                138       -    -138
ZSTD_count                                   362     181    -181
ZSTD_count_2segments                        1407     938    -469
ZSTD_insertBt1.constprop                    2689       -   -2689
ZSTD_compressBlock_btultra2                19990     423  -19567
ZSTD_compressBlock_btultra                 19633      15  -19618
ZSTD_initStats_ultra                       19825       -  -19825
ZSTD_compressBlock_btopt                   20374      12  -20362
ZSTD_compressBlock_btopt_extDict           29984      12  -29972
ZSTD_compressBlock_btultra_extDict         30718      15  -30703
ZSTD_compressBlock_btopt_dictMatchState    32689      12  -32677
ZSTD_compressBlock_btultra_dictMatchState   33574      15  -33559
Total: Before=6611828, After=6418562, chg -2.92%
```

[0] https://lkml.org/lkml/2021/11/14/189
[1] https://github.com/facebook/zstd/issues/2862

Link: https://lore.kernel.org/r/20211117014949.1169186-3-nickrterrell@gmail.com/
Link: https://lore.kernel.org/r/20211117201459.1194876-3-nickrterrell@gmail.com/

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Nick Terrell <terrelln@fb.com>
2021-11-18 13:15:33 -08:00
Nick Terrell
e0c1b49f5b lib: zstd: Upgrade to latest upstream zstd version 1.4.10
Upgrade to the latest upstream zstd version 1.4.10.

This patch is 100% generated from upstream zstd commit 20821a46f412 [0].

This patch is very large because it is transitioning from the custom
kernel zstd to using upstream directly. The new zstd follows upstreams
file structure which is different. Future update patches will be much
smaller because they will only contain the changes from one upstream
zstd release.

As an aid for review I've created a commit [1] that shows the diff
between upstream zstd as-is (which doesn't compile), and the zstd
code imported in this patch. The verion of zstd in this patch is
generated from upstream with changes applied by automation to replace
upstreams libc dependencies, remove unnecessary portability macros,
replace `/**` comments with `/*` comments, and use the kernel's xxhash
instead of bundling it.

The benefits of this patch are as follows:
1. Using upstream directly with automated script to generate kernel
   code. This allows us to update the kernel every upstream release, so
   the kernel gets the latest bug fixes and performance improvements,
   and doesn't get 3 years out of date again. The automation and the
   translated code are tested every upstream commit to ensure it
   continues to work.
2. Upgrades from a custom zstd based on 1.3.1 to 1.4.10, getting 3 years
   of performance improvements and bug fixes. On x86_64 I've measured
   15% faster BtrFS and SquashFS decompression+read speeds, 35% faster
   kernel decompression, and 30% faster ZRAM decompression+read speeds.
3. Zstd-1.4.10 supports negative compression levels, which allow zstd to
   match or subsume lzo's performance.
4. Maintains the same kernel-specific wrapper API, so no callers have to
   be modified with zstd version updates.

One concern that was brought up was stack usage. Upstream zstd had
already removed most of its heavy stack usage functions, but I just
removed the last functions that allocate arrays on the stack. I've
measured the high water mark for both compression and decompression
before and after this patch. Decompression is approximately neutral,
using about 1.2KB of stack space. Compression levels up to 3 regressed
from 1.4KB -> 1.6KB, and higher compression levels regressed from 1.5KB
-> 2KB. We've added unit tests upstream to prevent further regression.
I believe that this is a reasonable increase, and if it does end up
causing problems, this commit can be cleanly reverted, because it only
touches zstd.

I chose the bulk update instead of replaying upstream commits because
there have been ~3500 upstream commits since the 1.3.1 release, zstd
wasn't ready to be used in the kernel as-is before a month ago, and not
all upstream zstd commits build. The bulk update preserves bisectablity
because bugs can be bisected to the zstd version update. At that point
the update can be reverted, and we can work with upstream to find and
fix the bug.

Note that upstream zstd release 1.4.10 doesn't exist yet. I have cut a
staging branch at 20821a46f412 [0] and will apply any changes requested
to the staging branch. Once we're ready to merge this update I will cut
a zstd release at the commit we merge, so we have a known zstd release
in the kernel.

The implementation of the kernel API is contained in
zstd_compress_module.c and zstd_decompress_module.c.

[0] 20821a46f4
[1] e0fa481d0e

Signed-off-by: Nick Terrell <terrelln@fb.com>
Tested By: Paul Jones <paul@pauljones.id.au>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang v13.0.0 on x86-64
Tested-by: Jean-Denis Girard <jd.girard@sysnux.pf>
2021-11-08 16:55:32 -08:00