MFC r355182: Fix use-after-free in case of L2ARC prefetch failure.

In case L2ARC read failed, l2arc_read_done() creates _different_ ZIO
to read data from the original storage device. Unfortunately pointer
to the failed ZIO remains in hdr->b_l1hdr.b_acb->acb_zio_head, and if
some other read try to bump the ZIO priority, it will crash.

The problem is reproducible by corrupting L2ARC content and reading
some data with prefetch if l2arc_noprefetch tunable is changed to 0.
With the default setting the issue is probably not reproducible now.

MFC r348772: Restore ARC MFU/MRU pressure

Submitted by: Slawa Olhovchenkov <slw@zxy.spb.ru>
Sponsored by: Integros [integros.com]

MFC r345200: MFV r336930: 9284 arc_reclaim_thread has 2 jobs

`arc_reclaim_thread()` calls `arc_adjust()` after calling
`arc_kmem_reap_now()`; `arc_adjust()` signals `arc_get_data_buf()` to
indicate that we may no longer be `arc_is_overflowing()`.

The problem is, `arc_kmem_reap_now()` can take several seconds to
complete, has no impact on `arc_is_overflowing()`, but due to how the
code is structured, can impact how long the ARC will remain in the
`arc_is_overflowing()` state.

The fix is to use seperate threads to:

1. keep `arc_size` under `arc_c`, by calling `arc_adjust()`, which
improves `arc_is_overflowing()`

2. keep enough free memory in the system, by calling
`arc_kmem_reap_now()` plus `arc_shrink()`, which improves
`arc_available_memory()`.

illumos/illumos-gate@de753e34f9c399037936e8bc547d823bba9d4b0d

Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Tim Kordas <tim.kordas@joyent.com>
Approved by: Garrett D'Amore <garrett@damore.org>
Author: Brad Lewis <brad.lewis@delphix.com>

MFC r340311: Do not ignore arc_adjust() return value.

This covers scenario when ARC may not shrink as fast as it could:
1. arc_size < arc_c and arc_adjust() does not evict anything, returning
zero to arc_reclaim_thread();
2. arc_available_memory() reports memory pressure, which can not be
satisfied by arc_kmem_reap_now();
3. arc_shrink() reduces arc_c and calls arc_adjust(), return of which is
ignored;
4. even if the last arc_adjust() could not satisfy arc_size < arc_c,
arc_reclaim_thread() will still go to sleep, since the first one
returned zero.

MFC r344866: Add respective tunables to few ZFS sysctls.

MFC r337213: MFV r337212:
9465 ARC check for 'anon_size > arc_c/2' can stall the system

illumos/illumos-gate@abe1fd01ce5a83718c5a840daeab4abdaec1c104

Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Don Brady <don.brady@delphix.com>

MFC r337025: MFV r337022:
9403 assertion failed in arc_buf_destroy() when concurrently reading block with checksum error

This assertion (VERIFY) failure was reported when reading a block. Turns out
the problem is that if we get an i/o error (ECKSUM in this case), and there
are multiple concurrent ARC reads of the same block (from different clones),
then the ARC will put multiple buf's on the same ANON hdr, which isn't
supposed to happen, and then causes a panic when we try to arc_buf_destroy()
the buf.

illumos/illumos-gate@fa98e487a9619b7902f218663be219e787a57dad

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Approved by: Matt Ahrens <mahrens@delphix.com>
Author: Matthew Ahrens <mahrens@delphix.com>

MFC r334844, r336180, r336458

r334844

This originated from ZFS On Linux, as
https://github.com/zfsonlinux/zfs/commit/d4a72f23863382bdf6d0ae33196f5b5decbc48fd

During scans (scrubs or resilvers), it sorts the blocks in each transaction
group by block offset; the result can be a significant improvement. (On my
test system just now, which I put some effort to introduce fragmentation into
the pool since I set it up yesterday, a scrub went from 1h2m to 33.5m with the
changes.) I've seen similar rations on production systems.

r336180

Fix up some missed and mis-merges from the sequential scan code
(r334844). Most of the changes involve moving some code around to
reduce conflicts with future merges. One of the missing changes
included a notification on scrub cancellation.

r336458

Fix a couple of typos in r334844 noticed by Richard Kojedzinszky

Approved by: mav
Sponsored by: iXsystems, Inc

MFC r338416:
Re-compute the ARC size before computing the MFU target.

MFC r338142:
Set arc_kmem_cache_reap_retry_ms to 0 and make it configurable.

MFC r332523: 9433 Fix ARC hit rate

When the compressed ARC feature was added in commit d3c2ae1
the method of reference counting in the ARC was modified. As
part of this accounting change the arc_buf_add_ref() function
was removed entirely.

This would have be fine but the arc_buf_add_ref() function
served a second undocumented purpose of updating the ARC access
information when taking a hold on a dbuf. Without this logic
in place a cached dbuf would not migrate its associated
arc_buf_hdr_t to the MFU list. This would negatively impact
the ARC hit rate, particularly on systems with a small ARC.

This change reinstates the missing call to arc_access() from
dbuf_hold() by implementing a new arc_buf_access() function.

Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Tim Chase <tim@chase2k.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

MFC r331709: MFV r331708:
9321 arc_loan_compressed_buf() can increment arc_loaned_bytes by the wrong value

illumos/illumos-gate@9be12bd737714550277bd02b0c693db560976990

arc_loan_compressed_buf() increments arc_loaned_bytes by psize unconditionally
In the case of zfs_compressed_arc_enabled=0, when the buf is returned via
arc_return_buf(), if ARC_BUF_COMPRESSED(buf) is false, then arc_loaned_bytes
is decremented by lsize, not psize.

Switch to using arc_buf_size(buf), instead of psize, which will return
psize or lsize, depending on the result of ARC_BUF_COMPRESSED(buf).

Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>
Author: Allan Jude <allanjude@freebsd.org>

MFC r331404: MFV r331400:
8484 Implement aggregate sum and use for arc counters

In pursuit of improving performance on multi-core systems, we should
implements fanned out counters and use them to improve the performance of
some of the arc statistics. These stats are updated extremely frequently,
and can consume a significant amount of CPU time.

Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Paul Dagnelie <pcd@delphix.com>

MFC r329759:
9018 Replace kmem_cache_reap_now() with kmem_cache_reap_soon()

illumos/illumos-gate@36a64e62848b51ac5a9a5216e894ec723cfef14e

To prevent kmem_cache reaping from blocking other system resources, turn
kmem_cache_reap_now() (which blocks) into kmem_cache_reap_soon(). Callers
to kmem_cache_reap_soon() should use kmem_cache_reap_active(), which
exploits #9017's new taskq_empty().

Reviewed by: Bryan Cantrill <bryan@joyent.com>
Reviewed by: Dan McDonald <danmcd@joyent.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Yuri Pankov <yuripv@yuripv.net>
Author: Tim Kordas <tim.kordas@joyent.com>

FreeBSD does not use taskqueue for kmem caches reaping, so this change
is less dramatic then it is on Illumos, just limiting reaping to 1 time
per second. It may possibly be improved later, if needed.

MFC r329732: MFV r329502: 7614 zfs device evacuation/removal

illumos/illumos-gate@5cabbc6b49070407fb9610cfe73d4c0e0dea3e77

https://www.illumos.org/issues/7614:
This project allows top-level vdevs to be removed from the storage pool with
“zpool remove”, reducing the total amount of storage in the pool. This
operation copies all allocated regions of the device to be removed onto other
devices, recording the mapping from old to new location. After the removal is
complete, read and free operations to the removed (now “indirect”) vdev must
be remapped and performed at the new location on disk. The indirect mapping
table is kept in memory whenever the pool is loaded, so there is minimal
performance overhead when doing operations on the indirect vdev.

The size of the in-memory mapping table will be reduced when its entries
become “obsolete” because they are no longer used by any block pointers in
the pool. An entry becomes obsolete when all the blocks that use it are
freed. An entry can also become obsolete when all the snapshots that
reference it are deleted, and the block pointers that reference it have been
“remapped” in all filesystems/zvols (and clones). Whenever an indirect block
is written, all the block pointers in it will be “remapped” to their new
(concrete) locations if possible. This process can be accelerated by using
the “zfs remap” command to proactively rewrite all indirect blocks that
reference indirect (removed) vdevs.

Note that when a device is removed, we do not verify the checksum of the data
that is copied. This makes the process much faster, but if it were used on
redundant vdevs (i.e. mirror or raidz vdevs), it would be possible to copy
the wrong data, when we have the correct data on e.g. the other side of the
mirror. Therefore, mirror and raidz devices can not be removed.

Reviewed by: Alex Reece <alex@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Richard Laager <rlaager@wiktel.com>
Reviewed by: Tim Chase <tim@chase2k.com>
Approved by: Garrett D'Amore <garrett@damore.org>
Author: Prashanth Sreenivasa <pks@delphix.com>

MFC r329694: MFV r324198: 8081 Compiler warnings in zdb

illumos/illumos-gate@3f7978d02b206a6ebc5652c91aa9f42da6fbe00c
https://github.com/illumos/illumos-gate/commit/3f7978d02b206a6ebc5652c91aa9f42da6fbe00c

https://www.illumos.org/issues/8081
zdb(8) is full of minor problems that generate compiler warnings. On FreeBSD,
which uses -WError, the only way to build it is to disable all compiler
warnings. This makes it much harder to detect newly introduced bugs. We should
cleanup all the warnings.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Alan Somers <asomers@gmail.com>

MFC r329623: MFV r302649: 7016 arc_available_memory is not 32-bit safe

illumos/illumos-gate@0dd053d7d890618ea1fc697b07de364e69eb4190
https://github.com/illumos/illumos-gate/commit/0dd053d7d890618ea1fc697b07de364e69eb4190

https://www.illumos.org/issues/7016
upstream DLPX-39446 arc_available_memory is not 32-bit safe
https://github.com/delphix/delphix-os/commit/
6b353ea3b8a1610be22e71e657d051743c64190b
related to this upstream:
DLPX-38547 delphix engine hang
https://github.com/delphix/delphix-os/commit/
3183a567b3e8c62a74a65885ca60c86f3d693783
DLPX-38547 delphix engine hang (fix static global)
https://github.com/delphix/delphix-os/commit/
22ac551d8ef085ad66cc8f65e51ac372b12993b9
DLPX-38882 system hung waiting on free segment
https://github.com/delphix/delphix-os/commit/
cdd6beef7548cd3b12f0fc0328eeb3af540079c2

Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Gordon Ross <gordon.ross@nexenta.com>
Author: Prakash Surya <prakash.surya@delphix.com>

MFC r328776: ZFS ARC: restore illumos uses of 'needfree' that were removed in r325851

MFC r328246:
MFV r328245: 8856 arc_cksum_is_equal() doesn't take into account ABD-logic

illumos/illumos-gate@01a059ee0cdece49f47fd4d70086dd5bc7d0b0ff

https://www.illumos.org/issues/8856:
arc_cksum_is_equal() calls zio_push_transform() that requires abd_t*
(second arg), but a void* is passed.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Gordon Ross <gwr@nexenta.com>
Author: Roman Strashkin <roman.strashkin@nexenta.com>

MFC r326919:
Unregister the ARC lowmem event handler earlier in arc_fini().

MFC r325851:

remove the poor emulation of the IllumOS needfree global variable to prevent
the ARC reclaim thread running longer than needed.

Update the arc::needfree dtrace probe triggered in arc_lowmem() to also report
the value we may want to free.

Submitted by: Nikita Kozlov <nikita.kozlov at blade-group.com>
Reviewed by: avg
Approved by: avg
Sponsored by: blade
Differential Revision: https://reviews.freebsd.org/D12163

MFC r322222: MFV r322221: 7910 l2arc_write_buffers() may write beyond target_sz

FreeBD note: the essence of this change was committed to FreeBSD in
r314274. This commit catches up with differences between what was
committed to FreeBSD and what was committed to OpenZFS, mainly more
logical variable names.

illumos/illumos-gate@16a7e5ac116c85d965007a5f201104b564e82210
https://github.com/illumos/illumos-gate/commit/16a7e5ac116c85d965007a5f201104b564e82210

https://www.illumos.org/issues/7910
It seems that the change in issue #6950 resurrected the problem that was
earlier fixed by the change in issue #5219.
Please also see the following FreeBSD bug report:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=216178

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Andriy Gapon <avg@FreeBSD.org>

MFC r322239: MFV r322238: 7915 checks in l2arc_evict could use some cleaning up

illumos/illumos-gate@267ae6c3a88d2fc39276af66caafa978b0935b82
https://github.com/illumos/illumos-gate/commit/267ae6c3a88d2fc39276af66caafa978b0935b82

https://www.illumos.org/issues/7915
l2arc_evict() is strictly serialized with respect to
l2arc_write_buffers() and l2arc_write_done(). Normally, l2arc_evict()
and l2arc_write_buffers() are called from the same thread, so they can
not be concurrent. Also, l2arc_write_buffers() uses zio_wait() on the
parent zio of all cache zio-s. That ensures that l2arc_write_done()
is completed before l2arc_write_buffers() returns. Finally, if a
cache device is removed, then l2arc_evict() is called under SCL_ALL in
the exclusive mode. That ensures that it can not be concurrent with
the normal L2ARC accesses to the device (including writing and
evicting buffers). Given the above, some checks and actions in
l2arc_evict() do not make sense. For instance, it must never
encounter the write head header let alone remove it from the buffer
list.

Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Approved by: Matthew Ahrens <mahrens@delphix.com>
Author: Andriy Gapon <avg@FreeBSD.org>

MFC r323051:

Add sysctls for arc shrinking and growing values

The default value for arc_no_grow_shift may not be optimal when using
several GiB ARC. Expose it via sysctl allows users to tune it easily.

Also expose arc_grow_retry via sysctl for the same reason. The default value of
60s might, in case of intensive load, be too long.

Submitted by: Nikita Kozlov <nikita.kozlov@blade-group.com>
Reviewed by: mav, manu, bapt
Sponsored by: blade
Differential Revision: https://reviews.freebsd.org/D12144

MFC r320239: MFV r319950:
5220 L2ARC does not support devices that do not provide 512B access

FreeBSD note: the actual change has been in FreeBSD since r297848. This
commit accounts for integration of that change with subsequent changes,
especially r320156 (MFV of r318946) and r314274.

illumos/illumos-gate@403a8da73c64ff9dfb6230ba045c765a242213fb
https://github.com/illumos/illumos-gate/commit/403a8da73c64ff9dfb6230ba045c765a242213fb

https://www.illumos.org/issues/5220
There are disk devices that have logical sector size larger than 512B, for
example 4KB. That is, their physical sector size is larger than 512B and they
do not provide emulation for 512B sector sizes. For such devices both a data
offset and a data size must be properly aligned. L2ARC should arrange that
because it uses physical I/O.
zio_vdev_io_start() performs a necessary transformation if io_size is not
aligned to vdev_ashift, but that is done only for logical I/O. Something
similar should be done in L2ARC code.
* a temporary write buffer should be allocated if the original buffer is
not going to be compressed and its size is not aligned
* size of a temporary compression buffer should be ashift aligned
* for the reads, if a size of a target buffer is not sufficiently large and
it is not aligned then a temporary read buffer should be allocated

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Andriy Gapon <avg@FreeBSD.org>

MFC r320156, r320185, r320186, r320262, r320452, r321111:
MFV r318946: 8021 ARC buf data scatter-ization

illumos/illumos-gate@770499e185d15678ccb0be57ebc626ad18d93383
https://github.com/illumos/illumos-gate/commit/770499e185d15678ccb0be57ebc626ad1
8d93383

https://www.illumos.org/issues/8021
The ARC buf data project (known simply as "ABD" since its genesis in the ZoL
community) changes the way the ARC allocates `b_pdata` memory from using linea
r
`void *` buffers to using scatter/gather lists of fixed-size 1KB chunks. This
improves ZFS's performance by helping to defragment the address space occupied
by the ARC, in particular for cases where compressed ARC is enabled. It could
also ease future work to allocate pages directly from `segkpm` for minimal-
overhead memory allocations, bypassing the `kmem` subsystem.
This is essentially the same change as the one which recently landed in ZFS on
Linux, although they made some platform-specific changes while adapting this
work to their codebase:
1. Implemented the equivalent of the `segkpm` suggestion for future work
mentioned above to bypass issues that they've had with the Linux kernel memory
allocator.
2. Changed the internal representation of the ABD's scatter/gather list so it
could be used to pass I/O directly into Linux block device drivers. (This
feature is not available in the illumos block device interface yet.)

FreeBSD notes:
- the actual (default) chunk size is 4KB (despite the text above saying 1KB)
- we can try to reimplement ABDs, so that they are not permanently
mapped into the KVA unless explicitly requested, especially on
platforms with scarce KVA
- we can try to use unmapped I/O and avoid intermediate allocation of a
linear, virtual memory mapped buffer
- we can try to avoid extra data copying by referring to chunks / pages
in the original ABD

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Chris Williamson <chris.williamson@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Dan Kimmel <dan.kimmel@delphix.com>

MFC r319748: MFV r319738: 8155 simplify dmu_write_policy handling of pre-compressed buffers

illumos/illumos-gate@adaec86ad212d9fd756bee322934fa54d1258605
https://github.com/illumos/illumos-gate/commit/adaec86ad212d9fd756bee322934fa54d1258605

https://www.illumos.org/issues/8155
When writing pre-compressed buffers, arc_write() requires that the compression
algorithm used to compress the buffer matches the compression algorithm
requested by the zio_prop_t, which is set by dmu_write_policy().
This makes dmu_write_policy() and its callers a bit more complicated.
We can simplify this by making arc_write() trust the caller to supply the type
of pre-compressed buffer that it wants to write, and override the compression
setting in the zio_prop_t.

Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Matthew Ahrens <mahrens@delphix.com>

MFC r318925: MFV r316929: 6914 kernel virtual memory fragmentation leads to hang

illumos/illumos-gate@af868f46a5b794687741d5424de9e3a2d684a84a
https://github.com/illumos/illumos-gate/commit/af868f46a5b794687741d5424de9e3a2d684a84a

https://www.illumos.org/issues/6914

FreeBSD note: only a ZFS part of the change is merged, changes to the VM
subsystem are not ported (obviously). Also, now that FreeBSD has
vmem(9) we don't have to ifdef-out the code that uses it.

MFC r318924 (by avg):
arc_init: make code closer to upstream by introducing 'allmem' variable

All the differences in calculations are kept.
A comment about arc_max being 1/2 of all memory is fixed to reflect the
actual code that uses 5/8 as a factor.

MFC r318828: MFV r316917: 7968 multi-threaded spa_sync()

illumos/illumos-gate@94c2d0eb22e9624151ee84a7edbf7178e1bf4087
https://github.com/illumos/illumos-gate/commit/94c2d0eb22e9624151ee84a7edbf7178e1bf4087

https://www.illumos.org/issues/7968
spa_sync() iterates over all the dirty dnodes and processes each of them by
calling dnode_sync(). If there are many dirty dnodes (e.g. because we created
or removed a lot of files), the single thread of spa_sync() calling
dnode_sync() can become a bottleneck. Additionally, if many dnodes are dirtied
concurrently in open context (e.g. due to concurrent file creation), the
os_lock will experience lock contention via dnode_setdirty().
The solution is to track dirty dnodes on a multilist_t, and for spa_sync() to
use separate threads to process each of the sublists in the multilist.
On the concurrent file creation microbenchmark, the performance improvement
from dnode_setdirty() is up to 7%. Additionally, the wall clock time spent in
spa_sync() is reduced to 15%-40% of the single-threaded case. In terms of cost/
reward, once the other bottlenecks are addressed, fixing this bug will provide
a medium-large performance gain and require a medium amount of effort to
implement.

Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Matthew Ahrens <mahrens@delphix.com>

MFC r318827: MFV r316916: 7970 zfs_arc_num_sublists_per_state should be common to all multilists

illumos/illumos-gate@10fbdecb05f411234920f8d3c92c148d39106d7e
https://github.com/illumos/illumos-gate/commit/10fbdecb05f411234920f8d3c92c148d39106d7e

https://www.illumos.org/issues/7970
The global tunable zfs_arc_num_sublists_per_state is used by the ARC and
the dbuf cache, and other users are planned. We should change this
tunable to be common to all multilists.

Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Matthew Ahrens <mahrens@delphix.com>

MFC r317414: MFV 316894

7252 7628 compressed zfs send / receive

illumos/illumos-gate@5602294fda888d923d57a78bafdaf48ae6223dea
https://github.com/illumos/illumos-gate/commit/5602294fda888d923d57a78bafdaf48ae6223dea

https://www.illumos.org/issues/7252
This feature includes code to allow a system with compressed ARC enabled to
send data in its compressed form straight out of the ARC, and receive data in
its compressed form directly into the ARC.

https://www.illumos.org/issues/7628
We should have longer, more readable versions of the ZFS send / recv options.

7628 create long versions of ZFS send / receive options

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed by: David Quigley <dpquigl@davequigley.com>
Reviewed by: Thomas Caputi <tcaputi@datto.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Dan Kimmel <dan.kimmel@delphix.com>

MFC r315449:

Reduce ARC fragmentation threshold

Sponsored by: Multiplay

MFC r314913: MFV r314911: 7867 ARC space accounting leak

MFC r314274: l2arc: fix write size calculation broken by Compressed ARC commit

MFC 313879

MVF: 313876

7504 kmem_reap hangs spa_sync and administrative tasks

illumos/illumos-gate@405a5a0f5c3ab36cb76559467d1a62ba648bd809
https://github.com/illumos/illumos-gate/commit/405a5a0f5c3ab36cb76559467d1a62ba648bd80

https://www.illumos.org/issues/7504

We see long spa_sync(). We are waiting to hold dp_config_rwlock for writer. Some
other thread holds dp_config_rwlock for reader, then calls arc_get_data_buf(),
which finds that arc_is_overflowing()==B_TRUE. So it waits (while holding
dp_config_rwlock for reader) for arc_reclaim_thread to signal arc_reclaim_waiters_cv.
Before signaling, arc_reclaim_thread does arc_kmem_reap_now(), which takes ~seconds.

Author: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

MFC r313687: remove l2_padding_needed statistic from zfs arc

MFC r305561: MFV r305560:
7278 tuning zfs_arc_max does not impact arc_c_min

When changing zfs_arc_max (e.g. as zdb does), it may be set to less
than the default arc_c_min. arc_c_min should decrease to not be more than
arc_c_max, but it doesn't; therefore tuning of arc_c_max is ineffective.

Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Author: Matthew Ahrens <mahrens@delphix.com>

openzfs/openzfs@608764beadaf4bb71c5d8fe1818e8392ac66a61b

MFC r305323: MFV r302991: 6950 ARC should cache compressed data

illumos/illumos-gate@dcbf3bd6a1f1360fc1afcee9e22c6dcff7844bf2
https://github.com/illumos/illumos-gate/commit/dcbf3bd6a1f1360fc1afcee9e22c6dcff7844bf2

https://www.illumos.org/issues/6950
When reading compressed data from disk, the ARC should keep the compressed
block cached and only decompress it when consumers access the block. The
uncompressed data should be short-lived allowing the ARC to cache a much larger
amount of data. The DMU would also maintain a smaller cache of uncompressed
blocks to minimize the impact of decompressing frequently accessed blocks.

Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Don Brady <don.brady@intel.com>
Reviewed by: Richard Elling <Richard.Elling@RichardElling.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: George Wilson <george.wilson@delphix.com>

MFC r302838: 6513 partially filled holes lose birth time