Commit Graph

9 Commits

Author SHA1 Message Date
Richard Yao
ab8d9c1783 Cleanup: 64-bit kernel module parameters should use fixed width types
Various module parameters such as `zfs_arc_max` were originally
`uint64_t` on OpenSolaris/Illumos, but were changed to `unsigned long`
for Linux compatibility because Linux's kernel default module parameter
implementation did not support 64-bit types on 32-bit platforms. This
caused problems when porting OpenZFS to Windows because its LLP64 memory
model made `unsigned long` a 32-bit type on 64-bit, which created the
undesireable situation that parameters that should accept 64-bit values
could not on 64-bit Windows.

Upon inspection, it turns out that the Linux kernel module parameter
interface is extensible, such that we are allowed to define our own
types. Rather than maintaining the original type change via hacks to to
continue shrinking module parameters on 32-bit Linux, we implement
support for 64-bit module parameters on Linux.

After doing a review of all 64-bit kernel parameters (found via the man
page and also proposed changes by Andrew Innes), the kernel module
parameters fell into a few groups:

Parameters that were originally 64-bit on Illumos:

 * dbuf_cache_max_bytes
 * dbuf_metadata_cache_max_bytes
 * l2arc_feed_min_ms
 * l2arc_feed_secs
 * l2arc_headroom
 * l2arc_headroom_boost
 * l2arc_write_boost
 * l2arc_write_max
 * metaslab_aliquot
 * metaslab_force_ganging
 * zfetch_array_rd_sz
 * zfs_arc_max
 * zfs_arc_meta_limit
 * zfs_arc_meta_min
 * zfs_arc_min
 * zfs_async_block_max_blocks
 * zfs_condense_max_obsolete_bytes
 * zfs_condense_min_mapping_bytes
 * zfs_deadman_checktime_ms
 * zfs_deadman_synctime_ms
 * zfs_initialize_chunk_size
 * zfs_initialize_value
 * zfs_lua_max_instrlimit
 * zfs_lua_max_memlimit
 * zil_slog_bulk

Parameters that were originally 32-bit on Illumos:

 * zfs_per_txg_dirty_frees_percent

Parameters that were originally `ssize_t` on Illumos:

 * zfs_immediate_write_sz

Note that `ssize_t` is `int32_t` on 32-bit and `int64_t` on 64-bit. It
has been upgraded to 64-bit.

Parameters that were `long`/`unsigned long` because of Linux/FreeBSD
influence:

 * l2arc_rebuild_blocks_min_l2size
 * zfs_key_max_salt_uses
 * zfs_max_log_walking
 * zfs_max_logsm_summary_length
 * zfs_metaslab_max_size_cache_sec
 * zfs_min_metaslabs_to_flush
 * zfs_multihost_interval
 * zfs_unflushed_log_block_max
 * zfs_unflushed_log_block_min
 * zfs_unflushed_log_block_pct
 * zfs_unflushed_max_mem_amt
 * zfs_unflushed_max_mem_ppm

New parameters that do not exist in Illumos:

 * l2arc_trim_ahead
 * vdev_file_logical_ashift
 * vdev_file_physical_ashift
 * zfs_arc_dnode_limit
 * zfs_arc_dnode_limit_percent
 * zfs_arc_dnode_reduce_percent
 * zfs_arc_meta_limit_percent
 * zfs_arc_sys_free
 * zfs_deadman_ziotime_ms
 * zfs_delete_blocks
 * zfs_history_output_max
 * zfs_livelist_max_entries
 * zfs_max_async_dedup_frees
 * zfs_max_nvlist_src_size
 * zfs_rebuild_max_segment
 * zfs_rebuild_vdev_limit
 * zfs_unflushed_log_txg_max
 * zfs_vdev_max_auto_ashift
 * zfs_vdev_min_auto_ashift
 * zfs_vnops_read_chunk_size
 * zvol_max_discard_blocks

Rather than clutter the lists with commentary, the module parameters
that need comments are repeated below.

A few parameters were defined in Linux/FreeBSD specific code, where the
use of ulong/long is not an issue for portability, so we leave them
alone:

 * zfs_delete_blocks
 * zfs_key_max_salt_uses
 * zvol_max_discard_blocks

The documentation for a few parameters was found to be incorrect:

 * zfs_deadman_checktime_ms - incorrectly documented as int
 * zfs_delete_blocks - not documented as Linux only
 * zfs_history_output_max - incorrectly documented as int
 * zfs_vnops_read_chunk_size - incorrectly documented as long
 * zvol_max_discard_blocks - incorrectly documented as ulong

The documentation for these has been fixed, alongside the changes to
document the switch to fixed width types.

In addition, several kernel module parameters were percentages or held
ashift values, so being 64-bit never made sense for them. They have been
downgraded to 32-bit:

 * vdev_file_logical_ashift
 * vdev_file_physical_ashift
 * zfs_arc_dnode_limit_percent
 * zfs_arc_dnode_reduce_percent
 * zfs_arc_meta_limit_percent
 * zfs_per_txg_dirty_frees_percent
 * zfs_unflushed_log_block_pct
 * zfs_vdev_max_auto_ashift
 * zfs_vdev_min_auto_ashift

Of special note are `zfs_vdev_max_auto_ashift` and
`zfs_vdev_min_auto_ashift`, which were already defined as `uint64_t`,
and passed to the kernel as `ulong`. This is inherently buggy on big
endian 32-bit Linux, since the values would not be written to the
correct locations. 32-bit FreeBSD was unaffected because its sysctl code
correctly treated this as a `uint64_t`.

Lastly, a code comment suggests that `zfs_arc_sys_free` is
Linux-specific, but there is nothing to indicate to me that it is
Linux-specific. Nothing was done about that.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Original-patch-by: Andrew Innes <andrew.c12@gmail.com>
Original-patch-by: Jorgen Lundman <lundman@lundman.net>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #13984
Closes #14004
2022-10-13 10:03:29 -07:00
Ryan Moeller
9192f27c1d
Add zfs_multihost_interval tunable handler for FreeBSD
This tunable required a handler to be implemented for
ZFS_MODULE_PARAM_CALL.

Add the handler so the tunable can be declared in common code.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #10490
2020-06-23 13:32:42 -07:00
Olaf Faaland
060f0226e6 MMP interval and fail_intervals in uberblock
When Multihost is enabled, and a pool is imported, uberblock writes
include ub_mmp_delay to allow an importing node to calculate the
duration of an activity test.  This value, is not enough information.

If zfs_multihost_fail_intervals > 0 on the node with the pool imported,
the safe minimum duration of the activity test is well defined, but does
not depend on ub_mmp_delay:

zfs_multihost_fail_intervals * zfs_multihost_interval

and if zfs_multihost_fail_intervals == 0 on that node, there is no such
well defined safe duration, but the importing host cannot tell whether
mmp_delay is high due to I/O delays, or due to a very large
zfs_multihost_interval setting on the host which last imported the pool.
As a result, it may use a far longer period for the activity test than
is necessary.

This patch renames ub_mmp_sequence to ub_mmp_config and uses it to
record the zfs_multihost_interval and zfs_multihost_fail_intervals
values, as well as the mmp sequence.  This allows a shorter activity
test duration to be calculated by the importing host in most situations.
These values are also added to the multihost_history kstat records.

It calculates the activity test duration differently depending on
whether the new fields are present or not; for importing pools with
only ub_mmp_delay, it uses

(zfs_multihost_interval + ub_mmp_delay) * zfs_multihost_import_intervals

Which results in an activity test duration less sensitive to the leaf
count.

In addition, it makes a few other improvements:
* It updates the "sequence" part of ub_mmp_config when MMP writes
  in between syncs occur.  This allows an importing host to detect MMP
  on the remote host sooner, when the pool is idle, as it is not limited
  to the granularity of ub_timestamp (1 second).
* It issues writes immediately when zfs_multihost_interval is changed
  so remote hosts see the updated value as soon as possible.
* It fixes a bug where setting zfs_multihost_fail_intervals = 1 results
  in immediate pool suspension.
* Update tests to verify activity check duration is based on recorded
  tunable values, not tunable values on importing host.
* Update tests to verify the expected number of uberblocks have valid
  MMP fields - fail_intervals, mmp_interval, mmp_seq (sequence number),
  that sequence number is incrementing, and that uberblock values match
  tunable settings.

Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #7842
2019-03-21 12:47:57 -07:00
Olaf Faaland
db2af93d72 Increase default zfs_multihost_fail_intervals and import_intervals
By default, when multihost is enabled for a pool, the pool is
suspended if (zfs_multihost_fail_intervals*zfs_multihost_interval) ms
pass without a successful MMP write.  This is the recommended
configuration.

The default value for zfs_multihost_fail_intervals has been 5, and the
default value for zfs_multihost_interval has been 1000, so pool
suspension occurred at 5 seconds.

There have been multiple cases where a single misbehaving device in a
pool triggered a SCSI reset, and all I/O paused for 5-6 seconds.  This
in turn caused MMP to suspend the pool.

In the cases observed, the rest of the devices were healthy and the
pool was otherwise correctly performing I/O.  The reset was handled
correctly by ZFS, and by suspending the pool MMP made replacing the
device more difficult as well as forcing the host to be rebooted.

Increase the default value of zfs_multihost_fail_intervals to 10, so
that MMP tolerates up to 10 seconds of failed MMP writes before
suspending the pool.

Increase the default value of zfs_multihost_import_intervals to 20, to
maintain the 2:1 safety factor.  This results in a force import taking
approximately 20 seconds when MMP is enabled, with default values.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Andreas Dilger <andreas.dilger@whamcloud.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #7709 
Closes #8495
2019-03-13 09:50:48 -07:00
Olaf Faaland
3d31aad83e MMP writes rotate over leaves
Instead of choosing a leaf vdev quasi-randomly, by starting at the root
vdev and randomly choosing children, rotate over leaves to issue MMP
writes.  This fixes an issue in a pool whose top-level vdevs have
different numbers of leaves.

The issue is that the frequency at which individual leaves are chosen
for MMP writes is based not on the total number of leaves but based on
how many siblings the leaves have.

For example, in a pool like this:

       root-vdev
   +------+---------------+
vdev1                   vdev2
  |                       |
  |                +------+-----+-----+----+
disk1             disk2 disk3 disk4 disk5 disk6

vdev1 and vdev2 will each be chosen 50% of the time.  Every time vdev1
is chosen, disk1 will be chosen.  However, every time vdev2 is chosen,
disk2 is chosen 20% of the time.  As a result, disk1 will be sent 5x as
many MMP writes as disk2.

This may create wear issues in the case of SSDs.  It also reduces the
effectiveness of MMP as it depends on the writes being evenly
distributed for the case where some devices fail or are partitioned.

The new code maintains a list of leaf vdevs in the pool.  MMP records
the last leaf used for an MMP write in mmp->mmp_last_leaf.  To choose
the next leaf, MMP starts at mmp->mmp_last_leaf and traverses the list,
continuing from the head if the tail is reached.  It stops when a
suitable leaf is found or all leaves have been examined.

Added a test to verify MMP write distribution is even.

Reviewed-by: Tom Caputi <tcaputi@datto.com>
Reviewed-by: Kash Pande <kash@tripleback.net>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #7953
2019-03-12 10:37:06 -07:00
Olaf Faaland
d2160d0538 Record skipped MMP writes in multihost_history
Once per pass through the MMP thread's loop, the vdev tree is walked to
find a suitable leaf to write the next MMP block to.  If no such leaf is
found, the thread sleeps for a while and resumes at the top of the loop.

Add an entry to multihost_history when no leaf can be found, and record
the reason in the error column.  The error code for such entries is a
bitfield, displayed in hex:

0x1  At least one vdev (interior or leaf) was not writeable.
0x2  At least one writeable leaf vdev was found, but it had a pending
MMP write.

timestamp = the time in seconds since the epoch when no leaf could be
found originally.

duration = the time (in ns) during which no MMP block was written for
this reason.  This does not include the preceeding inter-write period
nor the following inter-write period.

vdev_guid = the number of sequential cycles of the MMP thread looop when
this occurred.

Sample output, truncated to fit:

For records of skipped MMP writes the right-most column, vdev_path, is
reported as "-".

id   txg  timestamp   error  duration    mmp_delay  vdev_guid     ...
936  11   1520036441  0      146264      891422313  1740883117838 ...
937  11   1520036441  0      163956      888356657  7320395061548 ...
938  11   1520036442  0      130690      885314969  7320395061548 ...
939  11   1520036442  0      2001068577  882296582  1740883117838 ...
940  11   1520036443  0      161806      882296582  7320395061548 ...
941  11   1520036443  0x2    0           998020546  1             ...
942  11   1520036444  0      136585      998020546  7320395061548 ...
943  11   1520036444  0x2    0           998020257  1             ...
944  11   1520036445  5      2002662964  994160219  1740883117838 ...
945  11   1520036445  0x2    998073118   994160219  3             ...
946  11   1520036447  0      247136      994160219  7320395061548 ...

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #7212
2018-03-06 15:15:15 -08:00
Olaf Faaland
7088545d01 Report duration and error in mmp_history entries
After an MMP write completes, update the relevant mmp_history entry
with the time between submission and completion, and the error
status of the write.

[faaland1@toss3a zfs]$ cat /proc/spl/kstat/zfs/pool/multihost
39 0 0x01 100 8800 69147946270893 72723903122926
id       txg     timestamp  error  duration   mmp_delay    vdev_guid
10607    1166    1518985089 0      138301     637785455    4882...
10608    1166    1518985089 0      136154     635407747    1151...
10609    1166    1518985089 0      803618560  633048078    9740...
10610    1166    1518985090 0      144826     633048078    4882...
10611    1166    1518985090 0      164527     666187671    1151...

Where duration = gethrtime_in_done_fn - gethrtime_at_submission, and
error = zio->io_error.

Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #7190
2018-02-22 15:34:34 -08:00
Olaf Faaland
0582e40322 Add callback for zfs_multihost_interval
Add a callback to wake all running mmp threads when
zfs_multihost_interval is changed.

This is necessary when the interval is changed from a very large value
to a significantly lower one, while pools are imported that have the
multihost property enabled.

Without this commit, the mmp thread does not wake up and detect the new
interval until after it has waited the old multihost interval time.  A
user monitoring mmp writes via the provided kstat would be led to
believe that the changed setting did not work.

Added a test in the ZTS under mmp to verify the new functionality is
working.

Added a test to ztest which starts and stops mmp threads, and calls into
the code to signal sleeping mmp threads, to test for deadlocks or
similar locking issues.

Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #6387
2017-07-25 13:22:20 -04:00
Olaf Faaland
379ca9cf2b Multi-modifier protection (MMP)
Add multihost=on|off pool property to control MMP.  When enabled
a new thread writes uberblocks to the last slot in each label, at a
set frequency, to indicate to other hosts the pool is actively imported.
These uberblocks are the last synced uberblock with an updated
timestamp.  Property defaults to off.

During tryimport, find the "best" uberblock (newest txg and timestamp)
repeatedly, checking for change in the found uberblock.  Include the
results of the activity test in the config returned by tryimport.
These results are reported to user in "zpool import".

Allow the user to control the period between MMP writes, and the
duration of the activity test on import, via a new module parameter
zfs_multihost_interval.  The period is specified in milliseconds.  The
activity test duration is calculated from this value, and from the
mmp_delay in the "best" uberblock found initially.

Add a kstat interface to export statistics about Multiple Modifier
Protection (MMP) updates. Include the last synced txg number, the
timestamp, the delay since the last MMP update, the VDEV GUID, the VDEV
label that received the last MMP update, and the VDEV path.  Abbreviated
output below.

$ cat /proc/spl/kstat/zfs/mypool/multihost
31 0 0x01 10 880 105092382393521 105144180101111
txg   timestamp  mmp_delay   vdev_guid   vdev_label vdev_path
20468    261337  250274925   68396651780       3    /dev/sda
20468    261339  252023374   6267402363293     1    /dev/sdc
20468    261340  252000858   6698080955233     1    /dev/sdx
20468    261341  251980635   783892869810      2    /dev/sdy
20468    261342  253385953   8923255792467     3    /dev/sdd
20468    261344  253336622   042125143176      0    /dev/sdab
20468    261345  253310522   1200778101278     2    /dev/sde
20468    261346  253286429   0950576198362     2    /dev/sdt
20468    261347  253261545   96209817917       3    /dev/sds
20468    261349  253238188   8555725937673     3    /dev/sdb

Add a new tunable zfs_multihost_history to specify the number of MMP
updates to store history for. By default it is set to zero meaning that
no MMP statistics are stored.

When using ztest to generate activity, for automated tests of the MMP
function, some test functions interfere with the test.  For example, the
pool is exported to run zdb and then imported again.  Add a new ztest
function, "-M", to alter ztest behavior to prevent this.

Add new tests to verify the new functionality.  Tests provided by
Giuseppe Di Natale.

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Reviewed-by: Ned Bass <bass6@llnl.gov>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Closes #745
Closes #6279
2017-07-13 13:54:00 -04:00