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Tiered early abort, zstd edition 

It turns out that "do LZ4 and zstd-1 both fail" is a great heuristic
for "don't even bother trying higher zstd tiers".

By way of illustration:
$ cat /incompress | mbuffer | zfs recv -o compression=zstd-12 evenfaster/lowcomp_1M_zstd12_normal
summary: 39.8 GiByte in  3min 40.2sec - average of  185 MiB/s
$ echo 3 | sudo tee /sys/module/zzstd/parameters/zstd_lz4_pass
3
$ cat /incompress | mbuffer -m 4G | zfs recv -o compression=zstd-12 evenfaster/lowcomp_1M_zstd12_patched
summary: 39.8 GiByte in 48.6sec - average of  839 MiB/s
$ sudo zfs list -p -o name,used,lused,ratio evenfaster/lowcomp_1M_zstd12_normal evenfaster/lowcomp_1M_zstd12_patched
NAME                                         USED        LUSED  RATIO
evenfaster/lowcomp_1M_zstd12_normal   39549931520  42721221632   1.08
evenfaster/lowcomp_1M_zstd12_patched  39626399744  42721217536   1.07
$ python3 -c "print(39626399744 - 39549931520)"
76468224
$

I'll take 76 MB out of 42 GB for > 4x speedup.

Reviewed-by: Allan Jude <allan@klarasystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Kjeld Schouten <kjeld@schouten-lebbing.nl>
Reviewed-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes #13244
This commit is contained in:
Rich Ercolani 2022-05-24 12:43:22 -04:00 committed by GitHub
parent 2e05765006
commit f375b23c02
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 134 additions and 6 deletions
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4
include/sys/zstd/zstd.h
View File

@ -78,6 +78,8 @@ typedef struct zfs_zstd_meta {
* kstat helper macros
*/
#define ZSTDSTAT(stat) (zstd_stats.stat.value.ui64)
#define ZSTDSTAT_ZERO(stat) \
(atomic_store_64(&zstd_stats.stat.value.ui64, 0))
#define ZSTDSTAT_ADD(stat, val) \
atomic_add_64(&zstd_stats.stat.value.ui64, (val))
#define ZSTDSTAT_SUB(stat, val) \
@ -90,6 +92,8 @@ void zstd_fini(void);
size_t zfs_zstd_compress(void *s_start, void *d_start, size_t s_len,
size_t d_len, int level);
size_t zfs_zstd_compress_wrap(void *s_start, void *d_start, size_t s_len,
size_t d_len, int level);
int zfs_zstd_get_level(void *s_start, size_t s_len, uint8_t *level);
int zfs_zstd_decompress_level(void *s_start, void *d_start, size_t s_len,
size_t d_len, uint8_t *level);

8
man/man4/zfs.4
View File

@ -2129,6 +2129,14 @@ However, if there are fewer than
metaslabs in the vdev, this functionality is disabled.
This ensures that we don't set aside an unreasonable amount of space for the ZIL.
.
.It Sy zfs_zstd_earlyabort_pass Ns = Ns Sy 1 Pq int
Whether heuristic for detection of incompressible data with zstd levels >= 3
using LZ4 and zstd-1 passes is enabled.
.
.It Sy zfs_zstd_abort_size Ns = Ns Sy 131072 Pq int
Minimal uncompressed size (inclusive) of a record before the early abort
heuristic will be attempted.
.
.It Sy zio_deadman_log_all Ns = Ns Sy 0 Ns | Ns 1 Pq int
If non-zero, the zio deadman will produce debugging messages
.Pq see Sy zfs_dbgmsg_enable

2
module/zfs/zio_compress.c
View File

@ -66,7 +66,7 @@ zio_compress_info_t zio_compress_table[ZIO_COMPRESS_FUNCTIONS] = {
{"gzip-9", 9, gzip_compress, gzip_decompress, NULL},
{"zle", 64, zle_compress, zle_decompress, NULL},
{"lz4", 0, lz4_compress_zfs, lz4_decompress_zfs, NULL},
{"zstd", ZIO_ZSTD_LEVEL_DEFAULT, zfs_zstd_compress,
{"zstd", ZIO_ZSTD_LEVEL_DEFAULT, zfs_zstd_compress_wrap,
zfs_zstd_decompress, zfs_zstd_decompress_level},
};

126
module/zstd/zfs_zstd.c
View File

@ -50,6 +50,10 @@
#include "lib/zstd.h"
#include "lib/common/zstd_errors.h"
static int zstd_earlyabort_pass = 1;
static int zstd_cutoff_level = ZIO_ZSTD_LEVEL_3;
static unsigned int zstd_abort_size = (128 * 1024);
static kstat_t *zstd_ksp = NULL;
typedef struct zstd_stats {
@ -62,6 +66,21 @@ typedef struct zstd_stats {
kstat_named_t zstd_stat_dec_header_inval;
kstat_named_t zstd_stat_com_fail;
kstat_named_t zstd_stat_dec_fail;
/*
* LZ4 first-pass early abort verdict
*/
kstat_named_t zstd_stat_lz4pass_allowed;
kstat_named_t zstd_stat_lz4pass_rejected;
/*
* zstd-1 second-pass early abort verdict
*/
kstat_named_t zstd_stat_zstdpass_allowed;
kstat_named_t zstd_stat_zstdpass_rejected;
/*
* We excluded this from early abort for some reason
*/
kstat_named_t zstd_stat_passignored;
kstat_named_t zstd_stat_passignored_size;
kstat_named_t zstd_stat_buffers;
kstat_named_t zstd_stat_size;
} zstd_stats_t;
@ -76,10 +95,44 @@ static zstd_stats_t zstd_stats = {
{ "decompress_header_invalid", KSTAT_DATA_UINT64 },
{ "compress_failed", KSTAT_DATA_UINT64 },
{ "decompress_failed", KSTAT_DATA_UINT64 },
{ "lz4pass_allowed", KSTAT_DATA_UINT64 },
{ "lz4pass_rejected", KSTAT_DATA_UINT64 },
{ "zstdpass_allowed", KSTAT_DATA_UINT64 },
{ "zstdpass_rejected", KSTAT_DATA_UINT64 },
{ "passignored", KSTAT_DATA_UINT64 },
{ "passignored_size", KSTAT_DATA_UINT64 },
{ "buffers", KSTAT_DATA_UINT64 },
{ "size", KSTAT_DATA_UINT64 },
};
#ifdef _KERNEL
static int
kstat_zstd_update(kstat_t *ksp, int rw)
{
ASSERT(ksp != NULL);
if (rw == KSTAT_WRITE && ksp == zstd_ksp) {
ZSTDSTAT_ZERO(zstd_stat_alloc_fail);
ZSTDSTAT_ZERO(zstd_stat_alloc_fallback);
ZSTDSTAT_ZERO(zstd_stat_com_alloc_fail);
ZSTDSTAT_ZERO(zstd_stat_dec_alloc_fail);
ZSTDSTAT_ZERO(zstd_stat_com_inval);
ZSTDSTAT_ZERO(zstd_stat_dec_inval);
ZSTDSTAT_ZERO(zstd_stat_dec_header_inval);
ZSTDSTAT_ZERO(zstd_stat_com_fail);
ZSTDSTAT_ZERO(zstd_stat_dec_fail);
ZSTDSTAT_ZERO(zstd_stat_lz4pass_allowed);
ZSTDSTAT_ZERO(zstd_stat_lz4pass_rejected);
ZSTDSTAT_ZERO(zstd_stat_zstdpass_allowed);
ZSTDSTAT_ZERO(zstd_stat_zstdpass_rejected);
ZSTDSTAT_ZERO(zstd_stat_passignored);
ZSTDSTAT_ZERO(zstd_stat_passignored_size);
}
return (0);
}
#endif
/* Enums describing the allocator type specified by kmem_type in zstd_kmem */
enum zstd_kmem_type {
ZSTD_KMEM_UNKNOWN = 0,
@ -377,6 +430,64 @@ zstd_enum_to_level(enum zio_zstd_levels level, int16_t *zstd_level)
}
size_t
zfs_zstd_compress_wrap(void *s_start, void *d_start, size_t s_len, size_t d_len,
int level)
{
int16_t zstd_level;
if (zstd_enum_to_level(level, &zstd_level)) {
ZSTDSTAT_BUMP(zstd_stat_com_inval);
return (s_len);
}
/*
* A zstd early abort heuristic.
*
* - Zeroth, if this is <= zstd-3, or < zstd_abort_size (currently
* 128k), don't try any of this, just go.
* (because experimentally that was a reasonable cutoff for a perf win
* with tiny ratio change)
* - First, we try LZ4 compression, and if it doesn't early abort, we
* jump directly to whatever compression level we intended to try.
* - Second, we try zstd-1 - if that errors out (usually, but not
* exclusively, if it would overflow), we give up early.
*
* If it works, instead we go on and compress anyway.
*
* Why two passes? LZ4 alone gets you a lot of the way, but on highly
* compressible data, it was losing up to 8.5% of the compressed
* savings versus no early abort, and all the zstd-fast levels are
* worse indications on their own than LZ4, and don't improve the LZ4
* pass noticably if stacked like this.
*/
size_t actual_abort_size = zstd_abort_size;
if (zstd_earlyabort_pass > 0 && zstd_level >= zstd_cutoff_level &&
s_len >= actual_abort_size) {
int pass_len = 1;
pass_len = lz4_compress_zfs(s_start, d_start, s_len, d_len, 0);
if (pass_len < d_len) {
ZSTDSTAT_BUMP(zstd_stat_lz4pass_allowed);
goto keep_trying;
}
ZSTDSTAT_BUMP(zstd_stat_lz4pass_rejected);
pass_len = zfs_zstd_compress(s_start, d_start, s_len, d_len,
ZIO_ZSTD_LEVEL_1);
if (pass_len == s_len || pass_len <= 0 || pass_len > d_len) {
ZSTDSTAT_BUMP(zstd_stat_zstdpass_rejected);
return (s_len);
}
ZSTDSTAT_BUMP(zstd_stat_zstdpass_allowed);
} else {
ZSTDSTAT_BUMP(zstd_stat_passignored);
if (s_len < actual_abort_size) {
ZSTDSTAT_BUMP(zstd_stat_passignored_size);
}
}
keep_trying:
return (zfs_zstd_compress(s_start, d_start, s_len, d_len, level));
}
/* Compress block using zstd */
size_t
zfs_zstd_compress(void *s_start, void *d_start, size_t s_len, size_t d_len,
@ -437,8 +548,10 @@ zfs_zstd_compress(void *s_start, void *d_start, size_t s_len, size_t d_len,
* too small, that is not a failure. Everything else is a
* failure, so increment the compression failure counter.
*/
if (ZSTD_getErrorCode(c_len) != ZSTD_error_dstSize_tooSmall) {
int err = ZSTD_getErrorCode(c_len);
if (err != ZSTD_error_dstSize_tooSmall) {
ZSTDSTAT_BUMP(zstd_stat_com_fail);
dprintf("Error: %s", ZSTD_getErrorString(err));
}
return (s_len);
}
@ -753,6 +866,9 @@ zstd_init(void)
if (zstd_ksp != NULL) {
zstd_ksp->ks_data = &zstd_stats;
kstat_install(zstd_ksp);
#ifdef _KERNEL
zstd_ksp->ks_update = kstat_zstd_update;
#endif
}
return (0);
@ -781,8 +897,8 @@ module_init(zstd_init);
module_exit(zstd_fini);
#endif
EXPORT_SYMBOL(zfs_zstd_compress);
EXPORT_SYMBOL(zfs_zstd_decompress_level);
EXPORT_SYMBOL(zfs_zstd_decompress);
EXPORT_SYMBOL(zfs_zstd_cache_reap_now);
ZFS_MODULE_PARAM(zfs, zstd_, earlyabort_pass, INT, ZMOD_RW,
"Enable early abort attempts when using zstd");
ZFS_MODULE_PARAM(zfs, zstd_, abort_size, UINT, ZMOD_RW,
"Minimal size of block to attempt early abort");
#endif