dbeb879699
dmu_object_alloc() is single-threaded, so when multiple threads are creating files in a single filesystem, they spend a lot of time waiting for the os_obj_lock. To improve performance of multi-threaded file creation, we must make dmu_object_alloc() typically not grab any filesystem-wide locks. The solution is to have a "next object to allocate" for each CPU. Each of these "next object"s is in a different block of the dnode object, so that concurrent allocation holds dnodes in different dbufs. When a thread's "next object" reaches the end of a chunk of objects (by default 4 blocks worth -- 128 dnodes), it will be reset to the per-objset os_obj_next, which will be increased by a chunk of objects (128). Only when manipulating the os_obj_next will we need to grab the os_obj_lock. This decreases lock contention dramatically, because each thread only needs to grab the os_obj_lock briefly, once per 128 allocations. This results in a 70% performance improvement to multi-threaded object creation (where each thread is creating objects in its own directory), from 67,000/sec to 115,000/sec, with 8 CPUs. Work sponsored by Intel Corp. Authored by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Ned Bass <bass6@llnl.gov> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Matthew Ahrens <mahrens@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> OpenZFS-issue: https://www.illumos.org/issues/8199 OpenZFS-commit: https://github.com/openzfs/openzfs/pull/374 Closes #4703 Closes #6117 |
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README.markdown
ZFS on Linux, which is also known as ZoL, is currently feature complete. It includes fully functional and stable SPA, DMU, ZVOL, and ZPL layers. And it's native!
Official Resources
Installation
Full documentation for installing ZoL on your favorite Linux distribution can be found at our site.
Contribute & Develop
We have a separate document with contribution guidelines.