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Matthew Ahrens
f8c0d7e1f6
`__vdev_disk_physio()` uses `abd_nr_pages_off()` to allocate a bio with a sufficient number of iovec's to process this zio (i.e. `nr_iovecs`/`bi_max_vecs`). If there are not enough iovec's in the bio, then additional bio's will be allocated. However, this is a sub-optimal code path. In particular, it requires several abd calls (to `abd_nr_pages_off()` and `abd_bio_map_off()`) which will have to walk the constituents of the ABD (the pages or the gang children) because they are looking for offsets > 0. For gang ABD's, `abd_nr_pages_off()` returns the number of iovec's needed for the first constituent, rather than the sum of all constituents (within the requested range). This always under-estimates the required number of iovec's, which causes us to always need several bio's. The end result is that `__vdev_disk_physio()` is usually O(n^2) for gang ABD's (and occasionally O(n^3), when more than 16 bio's are needed). This commit fixes `abd_nr_pages_off()`'s handling of gang ABD's, to correctly determine how many iovec's are needed, by adding up the number of iovec's for each of the gang children in the requested range. Reviewed-by: Mark Maybee <mark.maybee@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Brian Atkinson <batkinson@lanl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #11536
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 12-STABLE and 13-CURRENT.