bb29f1eb38
Holding a dbuf is a common operation which can become highly contended in dbuf_find() when acquiring the dbuf hash mutex. This is particularly true on Linux when reading/writing volumes since by default up to 32 threads from the zvol_taskq may be taking a hold of the same dbuf. This should also be observable on FreeBSD as long as there are enough processes accessing the volume concurrently. This is further aggregrated by the fact that only the block id will be unique when calculating the dbuf hash for a single volume. The objset id, object id, and level will be the same for data blocks. This has been observed to result in a somehwat less than uniform hash distribution and a longer than expected max hash chain depth (~20) on a large memory system (256 GB) using volumes. This commit improves the siutation by switching the hash mutex to an rwlock to allow concurrent lookups, and increasing DBUF_RWLOCKS from 2048 to 8192 to further reduce the odds of a hash collision. Reviewed-by: Tony Hutter <hutter2@llnl.gov> Reviewed-by: Alexander Motin <mav@FreeBSD.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #13405 |
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README.md
OpenZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the OpenZFS community. This repository contains the code for running OpenZFS on Linux and FreeBSD.
Official Resources
- Documentation - for using and developing this repo
- ZoL Site - Linux release info & links
- Mailing lists
- OpenZFS site - for conference videos and info on other platforms (illumos, OSX, Windows, etc)
Installation
Full documentation for installing OpenZFS on your favorite operating system can be found at the Getting Started Page.
Contribute & Develop
We have a separate document with contribution guidelines.
We have a Code of Conduct.
Release
OpenZFS is released under a CDDL license.
For more details see the NOTICE, LICENSE and COPYRIGHT files; UCRL-CODE-235197
Supported Kernels
- The
METAfile contains the officially recognized supported Linux kernel versions. - Supported FreeBSD versions are any supported branches and releases starting from 12.2-RELEASE.