3bd4df3841
As part of transaction group commit, dsl_pool_sync() sequentially calls dsl_dataset_sync() for each dirty dataset, which subsequently calls dmu_objset_sync(). dmu_objset_sync() in turn uses up to 75% of CPU cores to run sync_dnodes_task() in taskq threads to sync the dirty dnodes (files). There are two problems: 1. Each ZVOL in a pool is a separate dataset/objset having a single dnode. This means the objsets are synchronized serially, which leads to a bottleneck of ~330K blocks written per second per pool. 2. In the case of multiple dirty dnodes/files on a dataset/objset on a big system they will be sync'd in parallel taskq threads. However, it is inefficient to to use 75% of CPU cores of a big system to do that, because of (a) bottlenecks on a single write issue taskq, and (b) allocation throttling. In addition, if not for the allocation throttling sorting write requests by bookmarks (logical address), writes for different files may reach space allocators interleaved, leading to unwanted fragmentation. The solution to both problems is to always sync no more and (if possible) no fewer dnodes at the same time than there are allocators the pool. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Alexander Motin <mav@FreeBSD.org> Signed-off-by: Edmund Nadolski <edmund.nadolski@ixsystems.com> Closes #15197 |
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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.