MFC r337181: 9539 Make zvol operations use _by_dnode routines

Continues what was started in 7801 add more by-dnode routines by fully
converting zvols to avoid unnecessary dnode_hold() calls. This saves a
small amount of CPU time and slightly improves latencies of operations
on zvols.

illumos/illumos-gate@8dfe5547fbf0979fc1065a8b6fddc1e940a7cf4f

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Rick McNeal <rick.mcneal@nexenta.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Richard Yao <richard.yao@prophetstor.com>

MFC r336959: MFV r336958: 9337 zfs get all is slow due to uncached metadata

This project's goal is to make read-heavy channel programs and zfs(1m)
administrative commands faster by caching all the metadata that they will
need in the dbuf layer. This will prevent the data from being evicted, so
that any future call to i.e. zfs get all won't have to go to disk (very
much).

illumos/illumos-gate@adb52d9262f45a04318fc6e188fe2b7f59d989a5

Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Thomas Caputi <tcaputi@datto.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Matthew Ahrens <mahrens@delphix.com>

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 r329625: MFV r307315:
7301 zpool export -f should be able to interrupt file freeing

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Sanjay Nadkarni <sanjay.nadkarni@nexenta.com>
Reviewed by: Saso Kiselkov <saso.kiselkov@nexenta.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Author: Alek Pinchuk <alek@nexenta.com>

Closes #175

MFC r329363: read-behind / read-ahead support for zfs_getpages()

MFC r324011, r324016: MFV r323535: 8585 improve batching done in zil_commit()

FreeBSD notes:
- this MFV reverts FreeBSD commit r314549 to make the merge easier
- at present our emulation of cv_timedwait_hires is rather poor,
so I elected to use cv_timedwait_sbt directly
Please see the differential revision for details.
Unfortunately, I did not get any positive reviews, so there could be
bugs in the FreeBSD-specific piece of the merge.
Hence, the long MFC timeout.

illumos/illumos-gate@1271e4b10dfaaed576c08a812f466f6e81370e5e
https://github.com/illumos/illumos-gate/commit/1271e4b10dfaaed576c08a812f466f6e81370e5e

https://www.illumos.org/issues/8585
The current implementation of zil_commit() can introduce significant
latency, beyond what is inherent due to the latency of the underlying
storage. The additional latency comes from two main problems:
1. When there's outstanding ZIL blocks being written (i.e. there's
already a "writer thread" in progress), then any new calls to
zil_commit() will block waiting for the currently oustanding ZIL
blocks to complete. The blocks written for each "writer thread" is
coined a "batch", and there can only ever be a single "batch" being
written at a time. When a batch is being written, any new ZIL
transactions will have to wait for the next batch to be written,
which won't occur until the current batch finishes.
As a result, the underlying storage may not be used as efficiently
as possible. While "new" threads enter zil_commit() and are blocked
waiting for the next batch, it's possible that the underlying
storage isn't fully utilized by the current batch of ZIL blocks. In
that case, it'd be better to allow these new threads to generate
(and issue) a new ZIL block, such that it could be serviced by the
underlying storage concurrently with the other ZIL blocks that are
being serviced.
2. Any call to zil_commit() must wait for all ZIL blocks in its "batch"
to complete, prior to zil_commit() returning. The size of any given
batch is proportional to the number of ZIL transaction in the queue
at the time that the batch starts processing the queue; which
doesn't occur until the previous batch completes. Thus, if there's a
lot of transactions in the queue, the batch could be composed of
many ZIL blocks, and each call to zil_commit() will have to wait for
all of these writes to complete (even if the thread calling
zil_commit() only cared about one of the transactions in the batch).

Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Prakash Surya <prakash.surya@delphix.com>

MFC r322226: MFV r322223: 8378 crash due to bp in-memory modification of nopwrite block

illumos/illumos-gate@b7edcb940884114e61382937505433c4c38c0278
https://github.com/illumos/illumos-gate/commit/b7edcb940884114e61382937505433c4c38c0278

https://www.illumos.org/issues/8378
The problem is that zfs_get_data() supplies a stale zgd_bp to dmu_sync(), which
we then nopwrite against.
zfs_get_data() doesn't hold any DMU-related locks, so after it copies db_blkptr
to zgd_bp, dbuf_write_ready()
could change db_blkptr, and dbuf_write_done() could remove the dirty record.
dmu_sync() then sees the stale
BP and that the dbuf it not dirty, so it is eligible for nop-writing.
The fix is for dmu_sync() to copy db_blkptr to zgd_bp after acquiring the
db_mtx. We could still see a stale
db_blkptr, but if it is stale then the dirty record will still exist and thus
we won't attempt to nopwrite.

Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Matthew Ahrens <mahrens@delphix.com>

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 r318823: MFC r316914: 7801 add more by-dnode routines

illumos/illumos-gate@b0c42cd4706ba01ce158bd2bb1004f7e59eca5fe
https://github.com/illumos/illumos-gate/commit/b0c42cd4706ba01ce158bd2bb1004f7e59eca5fe

https://www.illumos.org/issues/7801
Add *_by_dnode() routines for accessing objects given their
dnode_t *, this is more efficient than accessing the object by
(objset_t *, uint64_t object). This change converts some but
not all of the existing consumers. As performance-sensitive
code paths are discovered they should be converted to use
these routines.
Ported from: https://github.com/zfsonlinux/zfs/commit/0eef1bde31d67091d3deed23fe2394f5a8bf2276

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: bzzz77 <bzzz.tomas@gmail.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 r316037: MFV: 315989

7603 xuio_stat_wbuf_* should be declared (void)

illumos/illumos-gate@99aa8b55058e512798eafbd71f72f916bdc10181
https://github.com/illumos/illumos-gate/commit/99aa8b55058e512798eafbd71f72f916bdc10181

https://www.illumos.org/issues/7603

The funcs are declared k&r style, where the args are not specified:

void xuio_stat_wbuf_copied();
They should be declared to take no arguments:

void xuio_stat_wbuf_copied(void);
Need to change both .c and .h.

Author: Prashanth Sreenivasa <pks@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

MFC r312535: MFV 312436

6569 large file delete can starve out write ops

illumos/illumos-gate@ff5177ee8bf9a355131ce2cc61ae2da6a5a6fdd6
https://github.com/illumos/illumos-gate/commit/ff5177ee8bf9a355131ce2cc61ae2da
6a5a6fdd6

https://www.illumos.org/issues/6569
The core issue I've found is that there is no throttle for how many
deletes get assigned to one TXG. As a results when deleting large files
we end up filling consecutive TXGs with deletes/frees, then write
throttling other (more important) ops.

There is an easy test case for this problem. Try deleting several
large files (at least 1/2 TB) while you do write ops on the same
pool. What we've seen is performance of these write ops (let's
call it sideload I/O) would drop to zero.

More specifically the problem is that dmu_free_long_range_impl()
can/will fill up all of the dirty data in the pool "instantly",
before many of the sideload ops can get in. So sideload
performance will be impacted until all the files are freed.

The solution we have tested at Nexenta (with positive results)
creates a relatively simple throttle for how many "free" ops we let
into one TXG.

However this solution exposes other problems that should also be
addressed. If we are to slow down freeing of data that means one
has to wait even longer (assuming vnode ref count of 1) to get shell
back after an rm or for NFS thread to finish the free-ing op.
To avoid this the proposed solution is to call zfs_inactive() async
for "large" files. Async freeing then begs for the reclaimed space
to be accounted for in the zpool's "freeing" prop.

The other issue with having a longer delete is the inability to
export/unmount for a longer period of time. The proposed solution
is to interrupt freeing of blocks when a fs is unmounted.

Author: Alek Pinchuk <alek@nexenta.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Sanjay Nadkarni <sanjay.nadkarni@nexenta.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

MFC r305340: MFC r305337:
7004 dmu_tx_hold_zap() does dnode_hold() 7x on same object

Using a benchmark which has 32 threads creating 2 million files in the
same directory, on a machine with 16 CPU cores, I observed poor
performance. I noticed that dmu_tx_hold_zap() was using about 30% of
all CPU, and doing dnode_hold() 7 times on the same object (the ZAP
object that is being held).

dmu_tx_hold_zap() keeps a hold on the dnode_t the entire time it is
running, in dmu_tx_hold_t:txh_dnode, so it would be nice to use the
dnode_t that we already have in hand, rather than repeatedly calling
dnode_hold(). To do this, we need to pass the dnode_t down through
all the intermediate calls that dmu_tx_hold_zap() makes, making these
routines take the dnode_t* rather than an objset_t* and a uint64_t
object number. In particular, the following routines will need to have
analogous *_by_dnode() variants created:

dmu_buf_hold_noread()
dmu_buf_hold()
zap_lookup()
zap_lookup_norm()
zap_count_write()
zap_lockdir()
zap_count_write()

This can improve performance on the benchmark described above by 100%,
from 30,000 file creations per second to 60,000. (This improvement is on
top of that provided by working around the object allocation issue. Peak
performance of ~90,000 creations per second was observed with 8 CPUs;
adding CPUs past that decreased performance due to lock contention.) The
CPU used by dmu_tx_hold_zap() was reduced by 88%, from 340 CPU-seconds
to 40 CPU-seconds.

Sponsored by: Intel Corp.

Closes #109

Reviewed by: Steve Gonczi <steve.gonczi@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Ned Bass <bass6@llnl.gov>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Author: Matthew Ahrens <mahrens@delphix.com>

openzfs/openzfs@d3e523d489a169ab36f9ec1b2a111a60a5563a9f

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