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ARC: Remove b_bufcnt/b_ebufcnt from ARC headers
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In most cases we do not care about exact number of buffers linked
to the header, we just need to know if it is zero, non-zero or one.
That can easily be checked just looking on b_buf pointer or in some
cases derefencing it.

b_ebufcnt is read only once, and in that case we already traverse
the list as part of arc_buf_remove(), so second traverse should not
be expensive.

This reduces L1 ARC header size by 8 bytes and full crypto header by
16 bytes, down to 176 and 232 bytes on FreeBSD respectively.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by:	Alexander Motin <[email protected]>
Sponsored by:	iXsystems, Inc.
Closes openzfs#15350
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@amotin @lundman
amotin authored and lundman committed Dec 11, 2023
1 parent 248301a commit f5b2fcb
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Showing 3 changed files with 42 additions and 83 deletions.
12 changes: 4 additions & 8 deletions include/os/linux/zfs/sys/trace_arc.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,6 @@ DECLARE_EVENT_CLASS(zfs_arc_buf_hdr_class,
__array(uint64_t, hdr_dva_word, 2)
__field(uint64_t, hdr_birth)
__field(uint32_t, hdr_flags)
__field(uint32_t, hdr_bufcnt)
__field(arc_buf_contents_t, hdr_type)
__field(uint16_t, hdr_psize)
__field(uint16_t, hdr_lsize)
Expand All @@ -70,7 +69,6 @@ DECLARE_EVENT_CLASS(zfs_arc_buf_hdr_class,
__entry->hdr_dva_word[1] = ab->b_dva.dva_word[1];
__entry->hdr_birth = ab->b_birth;
__entry->hdr_flags = ab->b_flags;
__entry->hdr_bufcnt = ab->b_l1hdr.b_bufcnt;
__entry->hdr_psize = ab->b_psize;
__entry->hdr_lsize = ab->b_lsize;
__entry->hdr_spa = ab->b_spa;
Expand All @@ -84,12 +82,12 @@ DECLARE_EVENT_CLASS(zfs_arc_buf_hdr_class,
__entry->hdr_refcount = ab->b_l1hdr.b_refcnt.rc_count;
),
TP_printk("hdr { dva 0x%llx:0x%llx birth %llu "
"flags 0x%x bufcnt %u type %u psize %u lsize %u spa %llu "
"flags 0x%x type %u psize %u lsize %u spa %llu "
"state_type %u access %lu mru_hits %u mru_ghost_hits %u "
"mfu_hits %u mfu_ghost_hits %u l2_hits %u refcount %lli }",
__entry->hdr_dva_word[0], __entry->hdr_dva_word[1],
__entry->hdr_birth, __entry->hdr_flags,
__entry->hdr_bufcnt, __entry->hdr_type, __entry->hdr_psize,
__entry->hdr_type, __entry->hdr_psize,
__entry->hdr_lsize, __entry->hdr_spa, __entry->hdr_state_type,
__entry->hdr_access, __entry->hdr_mru_hits,
__entry->hdr_mru_ghost_hits, __entry->hdr_mfu_hits,
Expand Down Expand Up @@ -192,7 +190,6 @@ DECLARE_EVENT_CLASS(zfs_arc_miss_class,
__array(uint64_t, hdr_dva_word, 2)
__field(uint64_t, hdr_birth)
__field(uint32_t, hdr_flags)
__field(uint32_t, hdr_bufcnt)
__field(arc_buf_contents_t, hdr_type)
__field(uint16_t, hdr_psize)
__field(uint16_t, hdr_lsize)
Expand Down Expand Up @@ -223,7 +220,6 @@ DECLARE_EVENT_CLASS(zfs_arc_miss_class,
__entry->hdr_dva_word[1] = hdr->b_dva.dva_word[1];
__entry->hdr_birth = hdr->b_birth;
__entry->hdr_flags = hdr->b_flags;
__entry->hdr_bufcnt = hdr->b_l1hdr.b_bufcnt;
__entry->hdr_psize = hdr->b_psize;
__entry->hdr_lsize = hdr->b_lsize;
__entry->hdr_spa = hdr->b_spa;
Expand Down Expand Up @@ -255,7 +251,7 @@ DECLARE_EVENT_CLASS(zfs_arc_miss_class,
__entry->zb_blkid = zb->zb_blkid;
),
TP_printk("hdr { dva 0x%llx:0x%llx birth %llu "
"flags 0x%x bufcnt %u psize %u lsize %u spa %llu state_type %u "
"flags 0x%x psize %u lsize %u spa %llu state_type %u "
"access %lu mru_hits %u mru_ghost_hits %u mfu_hits %u "
"mfu_ghost_hits %u l2_hits %u refcount %lli } "
"bp { dva0 0x%llx:0x%llx dva1 0x%llx:0x%llx dva2 "
Expand All @@ -264,7 +260,7 @@ DECLARE_EVENT_CLASS(zfs_arc_miss_class,
"blkid %llu }",
__entry->hdr_dva_word[0], __entry->hdr_dva_word[1],
__entry->hdr_birth, __entry->hdr_flags,
__entry->hdr_bufcnt, __entry->hdr_psize, __entry->hdr_lsize,
__entry->hdr_psize, __entry->hdr_lsize,
__entry->hdr_spa, __entry->hdr_state_type, __entry->hdr_access,
__entry->hdr_mru_hits, __entry->hdr_mru_ghost_hits,
__entry->hdr_mfu_hits, __entry->hdr_mfu_ghost_hits,
Expand Down
8 changes: 3 additions & 5 deletions include/sys/arc_impl.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -159,8 +159,6 @@ struct arc_write_callback {
* these two allocation states.
*/
typedef struct l1arc_buf_hdr {
uint8_t b_byteswap;

/* protected by arc state mutex */
arc_state_t *b_state;
multilist_node_t b_arc_node;
Expand All @@ -171,7 +169,7 @@ typedef struct l1arc_buf_hdr {
uint32_t b_mru_ghost_hits;
uint32_t b_mfu_hits;
uint32_t b_mfu_ghost_hits;
uint32_t b_bufcnt;
uint8_t b_byteswap;
arc_buf_t *b_buf;

/* self protecting */
Expand Down Expand Up @@ -434,12 +432,12 @@ typedef struct l2arc_dev {
*/
typedef struct arc_buf_hdr_crypt {
abd_t *b_rabd; /* raw encrypted data */
dmu_object_type_t b_ot; /* object type */
uint32_t b_ebufcnt; /* count of encrypted buffers */

/* dsobj for looking up encryption key for l2arc encryption */
uint64_t b_dsobj;

dmu_object_type_t b_ot; /* object type */

/* encryption parameters */
uint8_t b_salt[ZIO_DATA_SALT_LEN];
uint8_t b_iv[ZIO_DATA_IV_LEN];
Expand Down
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