9 Commits
| Author | SHA1 | Message | Date |
|---|---|---|---|
Matthew Ahrens
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cb682a173a |
Illumos #3618 ::zio dcmd does not show timestamp data
3618 ::zio dcmd does not show timestamp data Reviewed by: Adam Leventhal <ahl@delphix.com> Reviewed by: George Wilson <gwilson@zfsmail.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: Garrett D'Amore <garrett@damore.org> Approved by: Dan McDonald <danmcd@nexenta.com> References: http://www.illumos.org/issues/3618 illumos/illumos-gate@c55e05cb35 Notes on porting to ZFS on Linux: The original changeset mostly deals with mdb ::zio dcmd. However, in order to provide the requested functionality it modifies vdev and zio structures to keep the timing data in nanoseconds instead of ticks. It is these changes that are ported over in the commit in hand. One visible change of this commit is that the default value of 'zfs_vdev_time_shift' tunable is changed: zfs_vdev_time_shift = 6 to zfs_vdev_time_shift = 29 The original value of 6 was inherited from OpenSolaris and was subotimal - since it shifted the raw tick value - it didn't compensate for different tick frequencies on Linux and OpenSolaris. The former has HZ=1000, while the latter HZ=100. (Which itself led to other interesting performance anomalies under non-trivial load. The deadline scheduler delays the IO according to its priority - the lower priority the further the deadline is set. The delay is measured in units of "shifted ticks". Since the HZ value was 10 times higher, the delay units were 10 times shorter. Thus really low priority IO like resilver (delay is 10 units) and scrub (delay is 20 units) were scheduled much sooner than intended. The overall effect is that resilver and scrub IO consumed more bandwidth at the expense of the other IO.) Now that the bookkeeping is done is nanoseconds the shift behaves correctly for any tick frequency (HZ). Ported-by: Cyril Plisko <cyril.plisko@mountall.com> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1643 |
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George.Wilson
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cc92e9d0c3 |
3246 ZFS I/O deadman thread
Reviewed by: Matt Ahrens <matthew.ahrens@delphix.com> Reviewed by: Eric Schrock <eric.schrock@delphix.com> Reviewed by: Christopher Siden <chris.siden@delphix.com> Approved by: Garrett D'Amore <garrett@damore.org> NOTES: This patch has been reworked from the original in the following ways to accomidate Linux ZFS implementation *) Usage of the cyclic interface was replaced by the delayed taskq interface. This avoids the need to implement new compatibility code and allows us to rely on the existing taskq implementation. *) An extern for zfs_txg_synctime_ms was added to sys/dsl_pool.h because declaring externs in source files as was done in the original patch is just plain wrong. *) Instead of panicing the system when the deadman triggers a zevent describing the blocked vdev and the first pending I/O is posted. If the panic behavior is desired Linux provides other generic methods to panic the system when threads are observed to hang. *) For reference, to delay zios by 30 seconds for testing you can use zinject as follows: 'zinject -d <vdev> -D30 <pool>' References: illumos/illumos-gate@283b84606b https://www.illumos.org/issues/3246 Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1396 |
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Eric Dillmann
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9759c60f1a |
Illumos #3035 LZ4 compression support in ZFS and GRUB
3035 LZ4 compression support in ZFS and GRUB Reviewed by: Matthew Ahrens <mahrens@delphix.com> Reviewed by: Christopher Siden <christopher.siden@delphix.com> Reviewed by: George Wilson <george.wilson@delphix.com> Approved by: Christopher Siden <csiden@delphix.com> References: illumos/illumos-gate@a6f561b4ae https://www.illumos.org/issues/3035 http://wiki.illumos.org/display/illumos/LZ4+Compression+In+ZFS This patch has been slightly modified from the upstream Illumos version to be compatible with Linux. Due to the very limited stack space in the kernel a lz4 workspace kmem cache is used. Since we are using gcc we are also able to take advantage of the gcc optimized __builtin_ctz functions. Support for GRUB has been dropped from this patch. That code is available but those changes will need to made to the upstream GRUB package. Lastly, several hunks of dead code were dropped for clarity. They include the functions real_LZ4_uncompress(), LZ4_compressBound() and the Visual Studio specific hunks wrapped in _MSC_VER. Ported-by: Eric Dillmann <eric@jave.fr> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #1217 |
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Christopher Siden
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9ae529ec5d |
Illumos #2619 and #2747
2619 asynchronous destruction of ZFS file systems 2747 SPA versioning with zfs feature flags Reviewed by: Matt Ahrens <mahrens@delphix.com> Reviewed by: George Wilson <gwilson@delphix.com> Reviewed by: Richard Lowe <richlowe@richlowe.net> Reviewed by: Dan Kruchinin <dan.kruchinin@gmail.com> Approved by: Eric Schrock <Eric.Schrock@delphix.com> References: illumos/illumos-gate@53089ab7c8 illumos/illumos-gate@ad135b5d64 illumos changeset: 13700:2889e2596bd6 https://www.illumos.org/issues/2619 https://www.illumos.org/issues/2747 NOTE: The grub specific changes were not ported. This change must be made to the Linux grub packages. Ported-by: Brian Behlendorf <behlendorf1@llnl.gov> |
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Etienne Dechamps
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920dd524fb |
Add FASTWRITE algorithm for synchronous writes.
Currently, ZIL blocks are spread over vdevs using hint block pointers managed by the ZIL commit code and passed to metaslab_alloc(). Spreading log blocks accross vdevs is important for performance: indeed, using mutliple disks in parallel decreases the ZIL commit latency, which is the main performance metric for synchronous writes. However, the current implementation suffers from the following issues: 1) It would be best if the ZIL module was not aware of such low-level details. They should be handled by the ZIO and metaslab modules; 2) Because the hint block pointer is managed per log, simultaneous commits from multiple logs might use the same vdevs at the same time, which is inefficient; 3) Because dmu_write() does not honor the block pointer hint, indirect writes are not spread. The naive solution of rotating the metaslab rotor each time a block is allocated for the ZIL or dmu_sync() doesn't work in practice because the first ZIL block to be written is actually allocated during the previous commit. Consequently, when metaslab_alloc() decides the vdev for this block, it will do so while a bunch of other allocations are happening at the same time (from dmu_sync() and other ZILs). This means the vdev for this block is chosen more or less at random. When the next commit happens, there is a high chance (especially when the number of blocks per commit is slightly less than the number of the disks) that one disk will have to write two blocks (with a potential seek) while other disks are sitting idle, which defeats spreading and increases the commit latency. This commit introduces a new concept in the metaslab allocator: fastwrites. Basically, each top-level vdev maintains a counter indicating the number of synchronous writes (from dmu_sync() and the ZIL) which have been allocated but not yet completed. When the metaslab is called with the FASTWRITE flag, it will choose the vdev with the least amount of pending synchronous writes. If there are multiple vdevs with the same value, the first matching vdev (starting from the rotor) is used. Once metaslab_alloc() has decided which vdev the block is allocated to, it updates the fastwrite counter for this vdev. The rationale goes like this: when an allocation is done with FASTWRITE, it "reserves" the vdev until the data is written. Until then, all future allocations will naturally avoid this vdev, even after a full rotation of the rotor. As a result, pending synchronous writes at a given point in time will be nicely spread over all vdevs. This contrasts with the previous algorithm, which is based on the implicit assumption that blocks are written instantaneously after they're allocated. metaslab_fastwrite_mark() and metaslab_fastwrite_unmark() are used to manually increase or decrease fastwrite counters, respectively. They should be used with caution, as there is no per-BP tracking of fastwrite information, so leaks and "double-unmarks" are possible. There is, however, an assert in the vdev teardown code which will fire if the fastwrite counters are not zero when the pool is exported or the vdev removed. Note that as stated above, marking is also done implictly by metaslab_alloc(). ZIO also got a new FASTWRITE flag; when it is used, ZIO will pass it to the metaslab when allocating (assuming ZIO does the allocation, which is only true in the case of dmu_sync). This flag will also trigger an unmark when zio_done() fires. A side-effect of the new algorithm is that when a ZIL stops being used, its last block can stay in the pending state (allocated but not yet written) for a long time, polluting the fastwrite counters. To avoid that, I've implemented a somewhat crude but working solution which unmarks these pending blocks in zil_sync(), thus guaranteeing that linguering fastwrites will get pruned at each sync event. The best performance improvements are observed with pools using a large number of top-level vdevs and heavy synchronous write workflows (especially indirect writes and concurrent writes from multiple ZILs). Real-life testing shows a 200% to 300% performance increase with indirect writes and various commit sizes. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Issue #1013 |
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Brian Behlendorf
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86dd0fd922 |
Pre-allocate vdev I/O buffers
The vdev queue layer may require a small number of buffers when attempting to create aggregate I/O requests. Rather than attempting to allocate them from the global zio buffers, which is slow under memory pressure, it makes sense to pre-allocate them because... 1) These buffers are short lived. They are only required for the life of a single I/O at which point they can be used by the next I/O. 2) The maximum number of concurrent buffers needed by a vdev is small. It's roughly limited by the zfs_vdev_max_pending tunable which defaults to 10. By keeping a small list of these buffer per-vdev we can ensure one is always available when we need it. This significantly reduces contention on the vq->vq_lock, because we no longer need to perform a slow allocation under this lock. This is particularly important when memory is already low on the system. It would probably be wise to extend the use of these buffers beyond aggregate I/O and in to the raidz implementation. The inability to quickly allocate buffer for the parity stripes could result in similiar problems. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> |
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Garrett D'Amore
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a38718a63d |
Illumos #734: Use taskq_dispatch_ent() interface
It has been observed that some of the hottest locks are those of the zio taskqs. Contention on these locks can limit the rate at which zios are dispatched which limits performance. This upstream change from Illumos uses new interface to the taskqs which allow them to utilize a prealloc'ed taskq_ent_t. This removes the need to perform an allocation at dispatch time while holding the contended lock. This has the effect of improving system performance. Reviewed by: Albert Lee <trisk@nexenta.com> Reviewed by: Richard Lowe <richlowe@richlowe.net> Reviewed by: Alexey Zaytsev <alexey.zaytsev@nexenta.com> Reviewed by: Jason Brian King <jason.brian.king@gmail.com> Reviewed by: George Wilson <gwilson@zfsmail.com> Reviewed by: Adam Leventhal <ahl@delphix.com> Approved by: Gordon Ross <gwr@nexenta.com> References to Illumos issue: https://www.illumos.org/issues/734 Ported-by: Prakash Surya <surya1@llnl.gov> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #482 |
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Brian Behlendorf
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a69052be7f |
Initial zio delay timing
While there is no right maximum timeout for a disk IO we can start laying the ground work to measure how long they do take in practice. This change simply measures the IO time and if it exceeds 30s an event is posted for 'zpool events'. This value was carefully selected because for sd devices it implies that at least one timeout (SD_TIMEOUT) has occured. Unfortunately, even with FAILFAST set we may retry and request and not get an error. This behavior is strongly dependant on the device driver and how it is hooked in to the scsi error handling stack. However by setting the limit at 30s we can log the event even if no error was returned. Slightly longer term we can start recording these delays perhaps as a simple power-of-two histrogram. This histogram can then be reported as part of the 'zpool status' command when given an command line option. None of this code changes the internal behavior of ZFS. Currently it is simply for reporting excessively long delays. |
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Brian Behlendorf
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6283f55ea1 |
Support custom build directories and move includes
One of the neat tricks an autoconf style project is capable of is allow configurion/building in a directory other than the source directory. The major advantage to this is that you can build the project various different ways while making changes in a single source tree. For example, this project is designed to work on various different Linux distributions each of which work slightly differently. This means that changes need to verified on each of those supported distributions perferably before the change is committed to the public git repo. Using nfs and custom build directories makes this much easier. I now have a single source tree in nfs mounted on several different systems each running a supported distribution. When I make a change to the source base I suspect may break things I can concurrently build from the same source on all the systems each in their own subdirectory. wget -c http://github.com/downloads/behlendorf/zfs/zfs-x.y.z.tar.gz tar -xzf zfs-x.y.z.tar.gz cd zfs-x-y-z ------------------------- run concurrently ---------------------- <ubuntu system> <fedora system> <debian system> <rhel6 system> mkdir ubuntu mkdir fedora mkdir debian mkdir rhel6 cd ubuntu cd fedora cd debian cd rhel6 ../configure ../configure ../configure ../configure make make make make make check make check make check make check This change also moves many of the include headers from individual incude/sys directories under the modules directory in to a single top level include directory. This has the advantage of making the build rules cleaner and logically it makes a bit more sense. |