In addition import most recent arc_prune_async implementation as dependency
commit 25458cbef9
Author: Tim Chase <tim@chase2k.com>
Date: Wed Jul 13 07:42:40 2016 -0500
Limit the amount of dnode metadata in the ARC
Metadata-intensive workloads can cause the ARC to become permanently
filled with dnode_t objects as they're pinned by the VFS layer.
Subsequent data-intensive workloads may only benefit from about
25% of the potential ARC (arc_c_max - arc_meta_limit).
In order to help track metadata usage more precisely, the other_size
metadata arcstat has replaced with dbuf_size, dnode_size and bonus_size.
The new zfs_arc_dnode_limit tunable, which defaults to 10% of
zfs_arc_meta_limit, defines the minimum number of bytes which is desirable
to be consumed by dnodes. Attempts to evict non-metadata will trigger
async prune tasks if the space used by dnodes exceeds this limit.
The new zfs_arc_dnode_reduce_percent tunable specifies the amount by
which the excess dnode space is attempted to be pruned as a percentage of
the amount by which zfs_arc_dnode_limit is being exceeded. By default,
it tries to unpin 10% of the dnodes.
The problem of dnode metadata pinning was observed with the following
testing procedure (in this example, zfs_arc_max is set to 4GiB):
- Create a large number of small files until arc_meta_used exceeds
arc_meta_limit (3GiB with default tuning) and arc_prune
starts increasing.
- Create a 3GiB file with dd. Observe arc_mata_used. It will still
be around 3GiB.
- Repeatedly read the 3GiB file and observe arc_meta_limit as before.
It will continue to stay around 3GiB.
With this modification, space for the 3GiB file is gradually made
available as subsequent demands on the ARC are made. The previous behavior
can be restored by setting zfs_arc_dnode_limit to the same value as the
zfs_arc_meta_limit.
Signed-off-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #4345
Issue #4512
Issue #4773Closes#4858
commit 417104bdd3
Author: Ned Bass <bass6@llnl.gov>
Date: Thu Feb 26 12:24:11 2015 -0800
Use cached feature info in spa_add_feature_stats()
Avoid issuing I/O to the pool when retrieving feature flags information.
Trying to read the ZAPs from disk means that zpool clear would hang if
the pool is suspended and recovery would require a reboot. To keep the
feature stats resident in memory, we hang a cached nvlist off of the
spa. It is built up from disk the first time spa_add_feature_stats() is
called, and refreshed thereafter using the cached feature reference
counts. spa_add_feature_stats() gets called at pool import time so we
can be sure the cached nvlist will be available if the pool is later
suspended.
Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#3082
MFV:
commit ee36c709c3
Author: Gvozden Neskovic <neskovic@gmail.com>
Date: Sat Aug 27 20:12:53 2016 +0200
perf: 2.75x faster ddt_entry_compare()
First 256bits of ddt_key_t is a block checksum, which are expected
to be close to random data. Hence, on average, comparison only needs to
look at first few bytes of the keys. To reduce number of conditional
jump instructions, the result is computed as: sign(memcmp(k1, k2)).
Sign of an integer 'a' can be obtained as: `(0 < a) - (a < 0)` := {-1, 0, 1} ,
which is computed efficiently. Synthetic performance evaluation of
original and new algorithm over 1G random keys on 2.6GHz Intel(R) Xeon(R)
CPU E5-2660 v3:
old 6.85789 s
new 2.49089 s
perf: 2.8x faster vdev_queue_offset_compare() and vdev_queue_timestamp_compare()
Compute the result directly instead of using conditionals
perf: zfs_range_compare()
Speedup between 1.1x - 2.5x, depending on compiler version and
optimization level.
perf: spa_error_entry_compare()
`bcmp()` is not suitable for comparator use. Use `memcmp()` instead.
perf: 2.8x faster metaslab_compare() and metaslab_rangesize_compare()
perf: 2.8x faster zil_bp_compare()
perf: 2.8x faster mze_compare()
perf: faster dbuf_compare()
perf: faster compares in spa_misc
perf: 2.8x faster layout_hash_compare()
perf: 2.8x faster space_reftree_compare()
perf: libzfs: faster avl tree comparators
perf: guid_compare()
perf: dsl_deadlist_compare()
perf: perm_set_compare()
perf: 2x faster range_tree_seg_compare()
perf: faster unique_compare()
perf: faster vdev_cache _compare()
perf: faster vdev_uberblock_compare()
perf: faster fuid _compare()
perf: faster zfs_znode_hold_compare()
Signed-off-by: Gvozden Neskovic <neskovic@gmail.com>
Signed-off-by: Richard Elling <richard.elling@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#5033
When doing a read from disk, ZFS creates 3 ZIO's: a zio_null(), the
logical zio_read(), and then a physical zio. Currently, each of these
results in a separate taskq_dispatch(zio_execute).
On high-read-iops workloads, this causes a significant performance
impact. By processing all 3 ZIO's in a single taskq entry, we reduce the
overhead on taskq locking and context switching. We accomplish this by
allowing zio_done() to return a "next zio to execute" to zio_execute().
This results in a ~12% performance increase for random reads, from
96,000 iops to 108,000 iops (with recordsize=8k, on SSD's).
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: George Wilson <george.wilson@delphix.com>
Signed-off-by: Matthew Ahrens <mahrens@delphix.com>
External-issue: DLPX-59292
Closes#7736zfsonlinux/zfs@62840030a7
9580 Add a hash-table on top of nvlist to speed-up operations
illumos/illumos-gate@2ec7644aab
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Serapheim Dimitropoulos <serapheim@delphix.com>
illumos/illumos-gate@843c2111b1
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Matthew Ahrens <mahrens@delphix.com>
illumos/illumos-gate@48dd5e630c
Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Matthew Ahrens <mahrens@delphix.com>
illumos/illumos-gate@9ca527c3d3
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Matthew Ahrens <mahrens@delphix.com>
9465 ARC check for 'anon_size > arc_c/2' can stall the system
illumos/illumos-gate@abe1fd01ce
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>
The zfs_dbuf_evict_key TSD (thread-specific data) is not necessary - we can
instead pass a flag down in a few places to prevent recursive dbuf eviction.
Making this change has 3 benefits:
1. The code semantics are easier to understand.
2. On Linux, performance is improved, because creating/removing TSD values
(by setting to NULL vs non-NULL) is expensive, and we do it very often.
3. According to Nexenta, the current semantics can cause a deadlock when
concurrently calling dmu_objset_evict_dbufs() (which is rare today, but they
are working on a "parallel unmount" change that triggers this more easily)
illumos/illumos-gate@c2919acbea
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Andy Stormont <astormont@racktopsystems.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Matthew Ahrens <mahrens@delphix.com>
indirect vdevs that have been historically expanded
illumos/illumos-gate@11f6a9680e
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <gwilson@zfsmail.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
Reviewed by: Tim Chase <tim@chase2k.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Serapheim Dimitropoulos <serapheim@delphix.com>
illumos/illumos-gate@99a19144e8
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Matthew Ahrens <mahrens@delphix.com>
9438 Holes can lose birth time info if a block has a mix of birth times
Ultimately, the problem here is that when you truncate and write a file in
the same transaction group, the dbuf for the indirect block will be zeroed
out to deal with the truncation, and then written for the write. During
this process, we will lose hole birth time information for any holes in the
range. In the case where a dnode is being freed, we need to determine
whether the block should be converted to a higher-level hole in the zio
pipeline, and if so do it when the dnode is being synced out.
illumos/illumos-gate@738e2a3ce3
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Paul Dagnelie <pcd@delphix.com>
illumos/illumos-gate@dec267e7ea
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>
9424 ztest failure: "unprotected error in call to Lua API (Invalid value type 'f
unction' for key 'error')"
illumos/illumos-gate@fe3ba4d122
Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Don Brady <don.brady@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Matthew Ahrens <mahrens@delphix.com>
In the most fragmented real-world cases, this reduces memory used by the
mapping from ~1GB to ~50MB of RAM per 1TB of storage removed. Less
fragmented cases will typically also see around 50-100MB of RAM per 1TB
of storage.
illumos/illumos-gate@cfd63e1b1b
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Tim Chase <tim@chase2k.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Matthew Ahrens <mahrens@delphix.com>
Datasets that are deeply nested (~100 levels) are impractical. We just put
a limit of 50 levels to newly created datasets. Existing datasets should
work without a problem.
illumos/illumos-gate@5ac95da7d6
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>
Author: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
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@8dfe5547fb
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>
All objects after the last written or freed object are not supposed to
exist after receiving the stream. We should free them accordingly, as if
a freeobjects record for them had been included in the stream.
zfsonlinux/zfs@48fbb9ddbfillumos/illumos-gate@7864b8192b
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Paul Dagnelie <pcd@delphix.com>
9464 txg_kick() fails to see that we are quiescing, forcing transactions
to their next stages without leaving them accumulate changes
Ideally we would like txg_kick() to get triggered only when we are sure
that we are not syncing AND not quiescing any txg. This way we can kick
an open TXG to the quiescing state when we are sure that there is nothing
going on and we would benefit from the different states running
concurrently.
illumos/illumos-gate@fa41d87de9
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Andriy Gapon <avg@FreeBSD.org>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Serapheim Dimitropoulos <serapheim@delphix.com>
Updates to indirect blocks of spacemaps can contribute significantly to
write inflation. Therefore we want to reduce the indirect block size of
spacemaps from 128K to 16K.
illumos/illumos-gate@221813c13b
Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Albert Lee <trisk@forkgnu.org>
Reviewed by: Igor Kozhukhov <igor@dilos.org>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Matthew Ahrens <mahrens@delphix.com>
9426 metaslab size can exceed offset addressable by spacemap
metaslab size can exceed offset addressable by spacemap. The vdev can
address up to 2^63 * SPA_MAXBLOCKSIZE (512). A metaslab can address up to
2^47 * 2^vdev_ashift. Therefore we may need to increase the number of
metaslabs so that the maximum metaslab size is capped at the amount that
can be addressed by the spacemap. This should happen in
vdev_metaslab_set_size().
illumos/illumos-gate@b4bf0cf045
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Don Brady <don.brady@delphix.com>
9328 zap code can take advantage of c99
9329 panic in zap_leaf_lookup() due to concurrent zapification
illumos/illumos-gate@bf26014c55
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: Brad Lewis <brad.lewis@delphix.com>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Matthew Ahrens <mahrens@delphix.com>
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@fa98e487a9
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>
9421 zdb should detect and print out the number of "leaked" objects
9422 zfs diff and zdb should explicitly mark objects that are on the deleted queue
illumos/illumos-gate@20b5dafb42
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Approved by: Matt Ahrens <mahrens@delphix.com>
Author: Paul Dagnelie <pcd@delphix.com>
9102 zfs should be able to initialize storage devices
The first access to a disk block can incur a performance penalty on some
platforms (e.g. AWS's EBS, VMware VMDKs). Therefore it is recommended that
volumes be "thick provisioned", where supported by the platform (VMware).
Thick provisioning is time consuming and often is ignored. If the thick
provision step is omitted, customers will see suboptimal performance until
we have written to all parts of the LUN. ZFS should be able to initialize
any unused storage to remove any first-write penalty that exists.
illumos/illumos-gate@094e47e980
Reviewed by: John Wren Kennedy <john.kennedy@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: George Wilson <george.wilson@delphix.com>
illumos/illummos-gate@df477c0afa
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: John Kennedy <john.kennedy@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Paul Dagnelie <pcd@delphix.com>
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@adb52d9262
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>
We should use zfs_dbgmsg instead of spa_dbgmsg. Or at least,
metaslab_condense() should call zfs_dbgmsg because it's important and rare
enough to always log. It's possible that the message in zio_dva_allocate()
would be too high-frequency for zfs_dbgmsg.
illumos/illumos-gate@21f7c81cc1
Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Richard Elling <Richard.Elling@RichardElling.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Matthew Ahrens <mahrens@delphix.com>
Currently vdev_label_sync and vdev_uberblock_sync take a zio_t and assume
that its io_private is a pointer to the good_writes count. They should
instead accept this argument explicitly.
illumos/illumos-gate@a3b5583021
Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Matthew Ahrens <mahrens@delphix.com>
Mirrors are supposed to provide redundancy in the face of whole-disk failure
and silent damage (e.g. some data on disk is not right, but ZFS hasn't
detected the whole device as being broken). However, the current device
removal implementation bypasses some of the mirror's redundancy.
illumos/illumos-gate@3a4b1be953
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
Reviewed by: Sara Hartse <sara.hartse@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim@delphix.com>
Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed by: Tim Chase <tim@chase2k.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Matthew Ahrens <mahrens@delphix.com>
On high-end systems running async sequential write workloads, especially
NUMA systems with flash or NVMe storage, one significant performance
bottleneck is selecting a metaslab to do allocations from. This process
can be parallelized, providing significant performance increases for
these workloads.
illumos/illumos-gate@f78cdc34af
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Serapheim Dimitropoulos <serapheim.dimitro@delphix.com>
Reviewed by: Alexander Motin <mav@FreeBSD.org>
Approved by: Gordon Ross <gwr@nexenta.com>
Author: Paul Dagnelie <pcd@delphix.com>
The current space map encoding has the following disadvantages:
[1] Assuming 512 sector size each entry can represent at most 16MB for a segment.
This makes the encoding very inefficient for large regions of space.
[2] As vdev-wide space maps have started to be used by new features (i.e.
device removal, zpool checkpoint) we've started imposing limits in the
vdevs that can be used with them based on the maximum addressable offset
(currently 64PB for a top-level vdev).
The new remains backwards compatible with the old one. The introduced
two-word entry format, besides extending the limits imposed by the single-entry
layout, also includes a vdev field and some extra padding after its prefix.
The extra padding after the prefix should is reserved for future usage (e.g.
new prefixes for future encodings or new fields for flags). The new vdev field
not only makes the space maps more self-descriptive, but also opens the doors
for pool-wide space maps.
One final important note is that the number of bits used for vdevs is reduced
to 24 bits for blkptrs. That was decided as we don't know of any setups that
use more than 16M vdevs for the time being and
we wanted to fit the vdev field in the space map. In addition that gives us
some extra bits in dva_t.
illumos/illumos-gate@17f11284b4
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <gwilson@zfsmail.com>
Approved by: Gordon Ross <gwr@nexenta.com>
Author: Serapheim Dimitropoulos <serapheim@delphix.com>
illumos/illumos-gate@b6bf6e1540
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Prashanth Sreenivasa <pks@delphix.com>
Approved by: Matt Ahrens <mahrens@delphix.com>
Author: Pavel Zakharov <pavel.zakharov@delphix.com>
(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.
Approved by: mav
Sponsored by: iXsystems Inc
quatactl(2) mechanism. (Read-only at this point, however.)
In particular, this is to allow rpc.rquotad query quotas
for NFS mounts, allowing users to see their quotas on the
hosts using the datasets.
The changes specifically:
* Add new RPC entry points for querying quotas.
* Changes the library routines to allow non-UFS quotas.
* Changes rquotad to check for quotas on mounted filesystems,
rather than being limited to entries in /etc/fstab
* Lastly, adds a VFS entry-point for ZFS to query quotas.
Note that this makes one unavoidable behavioural change: if quotas
are enabled, then they can be queried, as opposed to the current
method of checking for quotas being specified in fstab. (With
ZFS, if there are user or group quotas, they're used, always.)
Reviewed by: delphij, mav
Approved by: mav
Sponsored by: iXsystems Inc
Differential Revision: https://reviews.freebsd.org/D15886
d4a72f2386
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.
Approved by: Alexander Motin
Obtained from: ZFS On Linux
Relnotes: Yes (improved scrub performance, with tunables)
Differential Revision: https://reviews.freebsd.org/D15562
When we're at our vnode limit, getnewvnode will call into the vnode LRU
cache to free up vnodes. If the vnode we try to recycle is a ZFS vnode we
end up, eventually, in zfs_rmnode. If the ZFS vnode we're recycling
represents something with extended attributes, zfs_rmnode will call
zfs_zget which will attempt to allocate another vnode. If the next vnode we
try to recycle is also a ZFS vnode representing something with extended
attributes we can recurse further. This ends up being unbounded and can end
up overflowing the stack.
In order to avoid this, restructure zfs_rmnode to simply add the extended
attribute directory's object ID to the unlinked set, thus not requiring the
allocation of a vnode. We then schedule a task that calls zfs_unlinked_drain
which will do the work of properly marking the vnodes for unlinking.
zfs_unlinked_drain is also called on mount so these will be cleaned up
there.
Reviewed by: avg, mav
Sponsored by: iXsystems, Inc.
Differential Revision: https://reviews.freebsd.org/D15342
Even though there do appear to be more artificial frames, with 12, stack
traces no longer list at all. Revert until a better, more stable value can
be determined.
