projects/linux·commit 4c388a8e

Merge tag 'zstd-for-linus-5.16-rc1' of git://github.com/terrelln/linux

4c388a8e · Linus Torvalds <[email protected]> · 2021-11-18 17:09:05 -08:00

Pull zstd fixes from Nick Terrell:
 "Fix stack usage on parisc & improve code size bloat

  This contains three commits:

   1. Fixes a minor unused variable warning reported by Kernel test
      robot [0].

   2. Improves the reported code bloat (-88KB / 374KB) [1] by outlining
      some functions that are unlikely to be used in performance
      sensitive workloads.

   3. Fixes the reported excess stack usage on parisc [2] by removing
      -O3 from zstd's compilation flags. -O3 triggered bugs in the
      hppa-linux-gnu gcc-8 compiler. -O2 performance is acceptable:
      neutral compression, about -1% decompression speed. We also reduce
      code bloat (-105KB / 374KB).

  After this our code bloat is cut from 374KB to 105KB with gcc-11. If
  we wanted to cut the remaining 105KB we'd likely have to trade
  signicant performance, so I want to say that this is enough for now.

  We should be able to get further gains without sacrificing speed, but
  that will take some significant optimization effort, and isn't
  suitable for a quick fix. I've opened an upstream issue [3] to track
  the code size, and try to avoid future regressions, and improve it in
  the long term"

Link: https://lore.kernel.org/linux-mm/[email protected]/T/ [0]
Link: https://lkml.org/lkml/2021/11/15/710 [1]
Link: https://lkml.org/lkml/2021/11/14/189 [2]
Link: https://github.com/facebook/zstd/issues/2867 [3]
Link: https://lore.kernel.org/r/[email protected]/
Link: https://lore.kernel.org/r/[email protected]/

* tag 'zstd-for-linus-5.16-rc1' of git://github.com/terrelln/linux:
  lib: zstd: Don't add -O3 to cflags
  lib: zstd: Don't inline functions in zstd_opt.c
  lib: zstd: Fix unused variable warning
Commit
4c388a8e740d3235a194f330c8ef327deef710f6
Parents
e26dd976 · 7416cdc9

Merge commit. Changes below are compared with the first parent: e26dd976.

Changes

4 files changed · +21 −2

FileStatusAddDelContent
lib/zstd/Makefilemodified+0−2View file
lib/zstd/common/compiler.hmodified+7−0View file
lib/zstd/compress/zstd_compress_superblock.cmodified+2−0View file
lib/zstd/compress/zstd_opt.cmodified+12−0View file

lib/zstd/Makefile

View file
diff --git a/lib/zstd/Makefile b/lib/zstd/Makefile
index 65218ec..fc45339 100644
--- a/lib/zstd/Makefile
+++ b/lib/zstd/Makefile
@@ -11,8 +11,6 @@
obj-$(CONFIG_ZSTD_COMPRESS) += zstd_compress.o
obj-$(CONFIG_ZSTD_DECOMPRESS) += zstd_decompress.o
-ccflags-y += -O3
-
zstd_compress-y := \
zstd_compress_module.o \
common/debug.o \

lib/zstd/common/compiler.h

View file
diff --git a/lib/zstd/common/compiler.h b/lib/zstd/common/compiler.h
index a1a051e..f5a9c70 100644
--- a/lib/zstd/common/compiler.h
+++ b/lib/zstd/common/compiler.h
@@ -16,6 +16,7 @@
*********************************************************/
/* force inlining */
+#if !defined(ZSTD_NO_INLINE)
#if (defined(__GNUC__) && !defined(__STRICT_ANSI__)) || defined(__cplusplus) || defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L /* C99 */
# define INLINE_KEYWORD inline
#else
@@ -24,6 +25,12 @@
#define FORCE_INLINE_ATTR __attribute__((always_inline))
+#else
+
+#define INLINE_KEYWORD
+#define FORCE_INLINE_ATTR
+
+#endif
/*
On MSVC qsort requires that functions passed into it use the __cdecl calling conversion(CC).

lib/zstd/compress/zstd_compress_superblock.c

View file
diff --git a/lib/zstd/compress/zstd_compress_superblock.c b/lib/zstd/compress/zstd_compress_superblock.c
index ee03e0a..b0610b2 100644
--- a/lib/zstd/compress/zstd_compress_superblock.c
+++ b/lib/zstd/compress/zstd_compress_superblock.c
@@ -411,6 +411,8 @@ static size_t ZSTD_seqDecompressedSize(seqStore_t const* seqStore, const seqDef*
const seqDef* sp = sstart;
size_t matchLengthSum = 0;
size_t litLengthSum = 0;
+ /* Only used by assert(), suppress unused variable warnings in production. */
+ (void)litLengthSum;
while (send-sp > 0) {
ZSTD_sequenceLength const seqLen = ZSTD_getSequenceLength(seqStore, sp);
litLengthSum += seqLen.litLength;

lib/zstd/compress/zstd_opt.c

View file
diff --git a/lib/zstd/compress/zstd_opt.c b/lib/zstd/compress/zstd_opt.c
index 0433705..dfc55e3 100644
--- a/lib/zstd/compress/zstd_opt.c
+++ b/lib/zstd/compress/zstd_opt.c
@@ -8,6 +8,18 @@
* You may select, at your option, one of the above-listed licenses.
*/
+/*
+ * Disable inlining for the optimal parser for the kernel build.
+ * It is unlikely to be used in the kernel, and where it is used
+ * latency shouldn't matter because it is very slow to begin with.
+ * We prefer a ~180KB binary size win over faster optimal parsing.
+ *
+ * TODO(https://github.com/facebook/zstd/issues/2862):
+ * Improve the code size of the optimal parser in general, so we
+ * don't need this hack for the kernel build.
+ */
+#define ZSTD_NO_INLINE 1
+
#include "zstd_compress_internal.h"
#include "hist.h"
#include "zstd_opt.h"