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Improve zfs send performance by bypassing the ARC #10067

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Merged
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Mar 10, 2020
Merged

Improve zfs send performance by bypassing the ARC #10067

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6 changes: 6 additions & 0 deletions include/sys/arc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,12 @@ typedef enum arc_flags
ARC_FLAG_COMPRESSED_ARC = 1 << 20,
ARC_FLAG_SHARED_DATA = 1 << 21,

/*
* Fail this arc_read() (with ENOENT) if the data is not already present
* in cache.
*/
ARC_FLAG_CACHED_ONLY = 1 << 22,

/*
* The arc buffer's compression mode is stored in the top 7 bits of the
* flags field, so these dummy flags are included so that MDB can
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1 change: 1 addition & 0 deletions include/sys/arc_impl.h
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Expand Up @@ -554,6 +554,7 @@ typedef struct arc_stats {
kstat_named_t arcstat_need_free;
kstat_named_t arcstat_sys_free;
kstat_named_t arcstat_raw_size;
kstat_named_t arcstat_cached_only_in_progress;
} arc_stats_t;

typedef enum free_memory_reason_t {
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19 changes: 18 additions & 1 deletion module/zfs/arc.c
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Expand Up @@ -548,7 +548,8 @@ arc_stats_t arc_stats = {
{ "demand_hit_prescient_prefetch", KSTAT_DATA_UINT64 },
{ "arc_need_free", KSTAT_DATA_UINT64 },
{ "arc_sys_free", KSTAT_DATA_UINT64 },
{ "arc_raw_size", KSTAT_DATA_UINT64 }
{ "arc_raw_size", KSTAT_DATA_UINT64 },
{ "cached_only_in_progress", KSTAT_DATA_UINT64 },
};

#define ARCSTAT_MAX(stat, val) { \
Expand Down Expand Up @@ -5563,6 +5564,13 @@ arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
if (HDR_IO_IN_PROGRESS(hdr)) {
zio_t *head_zio = hdr->b_l1hdr.b_acb->acb_zio_head;

if (*arc_flags & ARC_FLAG_CACHED_ONLY) {
mutex_exit(hash_lock);
ARCSTAT_BUMP(arcstat_cached_only_in_progress);
rc = SET_ERROR(ENOENT);
goto out;
}

ASSERT3P(head_zio, !=, NULL);
if ((hdr->b_flags & ARC_FLAG_PRIO_ASYNC_READ) &&
priority == ZIO_PRIORITY_SYNC_READ) {
Expand Down Expand Up @@ -5698,12 +5706,21 @@ arc_read(zio_t *pio, spa_t *spa, const blkptr_t *bp,
uint64_t size;
abd_t *hdr_abd;

if (*arc_flags & ARC_FLAG_CACHED_ONLY) {
rc = SET_ERROR(ENOENT);
if (hash_lock != NULL)
mutex_exit(hash_lock);
goto out;
}

/*
* Gracefully handle a damaged logical block size as a
* checksum error.
*/
if (lsize > spa_maxblocksize(spa)) {
rc = SET_ERROR(ECKSUM);
if (hash_lock != NULL)
mutex_exit(hash_lock);
goto out;
}

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