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shodanshok 7aef672b77 Read prefetched buffers from L2ARC 
Prefetched buffers are currently read from L2ARC if, and only if,
l2arc_noprefetch is set to non-default value of 0. This means that
a streaming read which can be served from L2ARC will instead engage
the main pool.

For example, consider what happens when a file is sequentially read:
- application requests contiguous data, engaging the prefetcher;
- ARC buffers are initially marked as prefetched but, as the calling
application consumes data, the prefetch tag is cleared;
- these "normal" buffers become eligible for L2ARC and are copied to it;
- re-reading the same file will *not* engage L2ARC even if it contains
the required buffers;
- main pool has to suffer another sequential read load, which (due to
most NCQ-enabled HDDs preferring sequential loads) can dramatically
increase latency for uncached random reads.

In other words, current behavior is to write data to L2ARC (wearing it)
without using the very same cache when reading back the same data. This
was probably useful many years ago to preserve L2ARC read bandwidth but,
with current SSD speed/size/price, it is vastly sub-optimal.

Setting l2arc_noprefetch=1, while enabling L2ARC to serve these reads,
means that even prefetched but unused buffers will be copied into L2ARC,
further increasing wear and load for potentially not-useful data.

This patch enable prefetched buffer to be read from L2ARC even when
l2arc_noprefetch=1 (default), increasing sequential read speed and
reducing load on the main pool without polluting L2ARC with not-useful
(ie: unused) prefetched data. Moreover, it clear users confusion about
L2ARC size increasing but not serving any IO when doing sequential
reads.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Gionatan Danti <g.danti@assyoma.it>
Closes #15451
 		2023-11-06 16:47:51 -08:00
..
THIRDPARTYLICENSE.cityhash OpenZFS 8484 - Implement aggregate sum and use for arc counters 2018-06-06 09:35:59 -07:00
THIRDPARTYLICENSE.cityhash.descrip OpenZFS 8484 - Implement aggregate sum and use for arc counters 2018-06-06 09:35:59 -07:00
abd.c Fix two abd_gang_add_gang() issues. 2023-05-05 09:17:55 -07:00
aggsum.c Remove bcopy(), bzero(), bcmp() 2022-03-15 15:13:42 -07:00
arc.c Read prefetched buffers from L2ARC 2023-11-06 16:47:51 -08:00
blake3_zfs.c blake3: fix up bogus checksums in face of cpu migration 2023-05-01 17:21:27 -07:00
blkptr.c Remove bcopy(), bzero(), bcmp() 2022-03-15 15:13:42 -07:00
bplist.c Use list_remove_head() where possible. 2023-06-09 10:12:52 -07:00
bpobj.c Add explicit prefetches to bpobj_iterate(). 2023-07-21 16:35:12 -07:00
bptree.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
bqueue.c Batch enqueue/dequeue for bqueue 2023-01-10 13:39:22 -08:00
brt.c zfs_clone_range should return a descriptive error codes 2023-08-25 13:33:40 -07:00
btree.c btree: Implement faster binary search algorithm 2023-05-26 10:03:12 -07:00
dataset_kstats.c zil: Add some more statistics. 2023-05-25 13:51:53 -07:00
dbuf.c dmu_buf_will_clone: change assertion to fix 32-bit compiler warning 2023-09-01 09:33:33 -07:00
dbuf_stats.c Revert "Reduce dbuf_find() lock contention" 2022-09-22 12:59:41 -07:00
ddt.c ddt_addref: remove unnecessary phys fill when refcount is 0 2023-06-30 09:01:58 -07:00
ddt_zap.c Pack our DDT ZAPs a bit denser. 2023-06-30 09:42:02 -07:00
dmu.c ZIL: Avoid dbuf_read() before dmu_sync(). 2023-08-25 11:58:44 -07:00
dmu_diff.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
dmu_object.c zfs redact fails when dnodesize=auto 2023-02-16 09:23:39 -08:00
dmu_objset.c Remove ARC/ZIO physdone callbacks. 2023-06-15 10:49:03 -07:00
dmu_recv.c Fix raw receive with different indirect block size. 2023-07-20 08:58:29 -07:00
dmu_redact.c Cleanup: Remove constant comparisons reported by CodeQL 2023-03-08 13:51:46 -08:00
dmu_send.c zdb: add -B option to generate backup stream 2023-06-05 11:54:42 -07:00
dmu_traverse.c Fix prefetching of indirect blocks while destroying 2023-03-24 10:20:07 -07:00
dmu_tx.c Use list_remove_head() where possible. 2023-06-09 10:12:52 -07:00
dmu_zfetch.c Adjust prefetch parameters. 2023-07-21 16:35:12 -07:00
dnode.c Fix raw receive with different indirect block size. 2023-07-20 08:58:29 -07:00
dnode_sync.c free_blocks(): Fix reports from 2016 PVS Studio FreeBSD report 2023-01-23 13:12:37 -08:00
dsl_bookmark.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
dsl_crypt.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
dsl_dataset.c Use list_remove_head() where possible. 2023-06-09 10:12:52 -07:00
dsl_deadlist.c Avoid extra snprintf() in dsl_deadlist_merge(). 2023-07-20 08:58:29 -07:00
dsl_deleg.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
dsl_destroy.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
dsl_dir.c Fix ENOSPC for extended quota 2023-09-28 14:28:21 -07:00
dsl_pool.c Remove lock from dsl_pool_need_dirty_delay() 2023-11-06 16:46:55 -08:00
dsl_prop.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
dsl_scan.c Do not request data L1 buffers on scan prefetch. 2023-07-21 16:35:12 -07:00
dsl_synctask.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
dsl_userhold.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
edonr_zfs.c Remove unused Edon-R variants 2023-03-14 15:59:58 -07:00
fm.c Use list_remove_head() where possible. 2023-06-09 10:12:52 -07:00
gzip.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
hkdf.c Remove bcopy(), bzero(), bcmp() 2022-03-15 15:13:42 -07:00
lz4.c lz4: Cherrypick fix for CVE-2021-3520 2022-01-12 16:14:36 -08:00
lz4_zfs.c Updated the lz4 decompressor 2022-01-07 10:36:49 -08:00
lzjb.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
metaslab.c Reduce number of metaslab preload taskq threads. 2023-10-07 09:08:20 -07:00
mmp.c Allow MMP to bypass waiting for other threads 2023-04-19 13:22:59 -07:00
multilist.c Cleanup: Specify unsignedness on things that should not be signed 2022-09-27 16:42:41 -07:00
objlist.c Implement Redacted Send/Receive 2019-06-19 09:48:12 -07:00
pathname.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
range_tree.c btree: Implement faster binary search algorithm 2023-05-26 10:03:12 -07:00
refcount.c Switch refcount tracking from lists to AVL-trees. 2023-06-14 08:02:27 -07:00
rrwlock.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
sa.c Cleanup: Remove constant comparisons reported by CodeQL 2023-03-08 13:51:46 -08:00
sha2_zfs.c Add generic implementation handling and SHA2 impl 2023-03-02 13:52:21 -08:00
skein_zfs.c Remove bcopy(), bzero(), bcmp() 2022-03-15 15:13:42 -07:00
spa.c import: require force when cachefile hostid doesn't match on-disk 2023-10-07 09:08:20 -07:00
spa_checkpoint.c Cleanup: 64-bit kernel module parameters should use fixed width types 2022-10-13 10:03:29 -07:00
spa_config.c Add mutex_enter_interruptible() for interruptible sleeping IOCTLs 2023-11-06 16:47:41 -08:00
spa_errlog.c Update the MOS directory on spa_upgrade_errlog() 2023-09-19 08:51:00 -07:00
spa_history.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
spa_log_spacemap.c Address warnings about possible division by zero from clangsa 2022-11-03 09:58:14 -07:00
spa_misc.c status: report pool suspension state under failmode=continue 2023-09-22 16:13:20 -07:00
spa_stats.c Cleanup: Specify unsignedness on things that should not be signed 2022-09-27 16:42:41 -07:00
space_map.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
space_reftree.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
txg.c Another set of vdev queue optimizations. 2023-06-27 09:09:48 -07:00
uberblock.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
unique.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev.c Set spa_ccw_fail_time=0 when expanding a vdev. 2023-11-06 16:46:25 -08:00
vdev_draid.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
vdev_draid_rand.c Distributed Spare (dRAID) Feature 2020-11-13 13:51:51 -08:00
vdev_indirect.c Don't emit cksum_{actual_expected} in ereport.fs.zfs.checksum events 2023-07-21 16:35:12 -07:00
vdev_indirect_births.c Remove bcopy(), bzero(), bcmp() 2022-03-15 15:13:42 -07:00
vdev_indirect_mapping.c Remove bcopy(), bzero(), bcmp() 2022-03-15 15:13:42 -07:00
vdev_initialize.c Add the ability to uninitialize 2023-05-18 10:02:20 -07:00
vdev_label.c Report ashift of L2ARC devices in zdb 2023-10-03 09:06:07 -07:00
vdev_mirror.c Improve too large physical ashift handling 2022-09-08 10:30:53 -07:00
vdev_missing.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_queue.c Another set of vdev queue optimizations. 2023-06-27 09:09:48 -07:00
vdev_raidz.c Don't emit cksum_{actual_expected} in ereport.fs.zfs.checksum events 2023-07-21 16:35:12 -07:00
vdev_raidz_math.c Miscellaneous FreBSD compilation bugfixes 2023-04-06 10:35:02 -07:00
vdev_raidz_math_aarch64_neon.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_raidz_math_aarch64_neon_common.h Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_raidz_math_aarch64_neonx2.c Fix Clang 15 compilation errors 2022-11-30 13:46:26 -08:00
vdev_raidz_math_avx2.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_raidz_math_avx512bw.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_raidz_math_avx512f.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_raidz_math_impl.h Cleanup Raid-Z Typo fixes 2022-09-06 09:43:21 -07:00
vdev_raidz_math_powerpc_altivec.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_raidz_math_powerpc_altivec_common.h Linux ppc64le ieee128 compat: Do not redefine __asm on external headers 2023-01-13 10:58:58 -08:00
vdev_raidz_math_scalar.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_raidz_math_sse2.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_raidz_math_ssse3.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_rebuild.c Tweak rebuild in-flight hard limit 2023-10-03 09:06:07 -07:00
vdev_removal.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
vdev_root.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
vdev_trim.c Zpool can start allocating from metaslab before TRIMs have completed 2023-10-12 11:05:20 -07:00
zap.c Cleanup: Use NULL when doing NULL pointer comparisons 2023-01-12 16:00:37 -08:00
zap_leaf.c Cleanup: Remove constant comparisons reported by CodeQL 2023-03-08 13:51:46 -08:00
zap_micro.c btree: Implement faster binary search algorithm 2023-05-26 10:03:12 -07:00
zcp.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
zcp_get.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
zcp_global.c OpenZFS 8600 - ZFS channel programs - snapshot 2018-02-08 15:29:24 -08:00
zcp_iter.c nvpair: Constify string functions 2023-03-14 15:25:50 -07:00
zcp_set.c Support setting user properties in a channel program 2020-02-14 13:41:42 -08:00
zcp_synctask.c Add zfs.sync.snapshot_rename 2022-09-02 13:31:19 -07:00
zfeature.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
zfs_byteswap.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
zfs_chksum.c Add generic implementation handling and SHA2 impl 2023-03-02 13:52:21 -08:00
zfs_fm.c Don't emit cksum_{actual_expected} in ereport.fs.zfs.checksum events 2023-07-21 16:35:12 -07:00
zfs_fuid.c Use list_remove_head() where possible. 2023-06-09 10:12:52 -07:00
zfs_impl.c Add generic implementation handling and SHA2 impl 2023-03-02 13:52:21 -08:00
zfs_ioctl.c Add mutex_enter_interruptible() for interruptible sleeping IOCTLs 2023-11-06 16:47:41 -08:00
zfs_log.c Fix VERIFY(!zil_replaying(zilog, tx)) panic 2023-04-17 16:42:09 -07:00
zfs_onexit.c Use list_remove_head() where possible. 2023-06-09 10:12:52 -07:00
zfs_quota.c Implementation of block cloning for ZFS 2023-03-10 11:59:53 -08:00
zfs_ratelimit.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
zfs_replay.c Linux 6.3 compat: idmapped mount API changes 2023-04-10 14:15:36 -07:00
zfs_rlock.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
zfs_sa.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
zfs_vnops.c Fix block cloning between unencrypted and encrypted datasets 2023-11-06 10:40:50 -08:00
zil.c Large sync writes perform worse with slog 2023-11-06 16:33:23 -08:00
zio.c Update outdated assertion from zio_write_compress 2023-08-26 11:18:11 -07:00
zio_checksum.c Don't emit cksum_{actual_expected} in ereport.fs.zfs.checksum events 2023-07-21 16:35:12 -07:00
zio_compress.c Skip memory allocation when compressing holes 2023-02-27 14:41:02 -08:00
zio_inject.c Cleanup: Switch to strlcpy from strncpy 2022-09-27 16:35:29 -07:00
zle.c Replace dead opensolaris.org license link 2022-07-11 14:16:13 -07:00
zrlock.c Micro-optimize zrl_remove() 2022-11-29 09:26:03 -08:00
zthr.c Switch from _Noreturn to __attribute__((noreturn)) 2022-03-23 08:51:00 -07:00
zvol.c ZIL: Second attempt to reduce scope of zl_issuer_lock. 2023-08-25 11:58:44 -07:00