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Giuseppe Di Natale 1b7c1e5ce9 OpenZFS 7578 - Fix/improve some aspects of ZIL writing
- After some ZIL changes 6 years ago zil_slog_limit got partially broken
due to zl_itx_list_sz not updated when async itx'es upgraded to sync.
Actually because of other changes about that time zl_itx_list_sz is not
really required to implement the functionality, so this patch removes
some unneeded broken code and variables.

 - Original idea of zil_slog_limit was to reduce chance of SLOG abuse by
single heavy logger, that increased latency for other (more latency critical)
loggers, by pushing heavy log out into the main pool instead of SLOG.  Beside
huge latency increase for heavy writers, this implementation caused double
write of all data, since the log records were explicitly prepared for SLOG.
Since we now have I/O scheduler, I've found it can be much more efficient
to reduce priority of heavy logger SLOG writes from ZIO_PRIORITY_SYNC_WRITE
to ZIO_PRIORITY_ASYNC_WRITE, while still leave them on SLOG.

 - Existing ZIL implementation had problem with space efficiency when it
has to write large chunks of data into log blocks of limited size.  In some
cases efficiency stopped to almost as low as 50%.  In case of ZIL stored on
spinning rust, that also reduced log write speed in half, since head had to
uselessly fly over allocated but not written areas.  This change improves
the situation by offloading problematic operations from z*_log_write() to
zil_lwb_commit(), which knows real situation of log blocks allocation and
can split large requests into pieces much more efficiently.  Also as side
effect it removes one of two data copy operations done by ZIL code WR_COPIED
case.

 - While there, untangle and unify code of z*_log_write() functions.
Also zfs_log_write() alike to zvol_log_write() can now handle writes crossing
block boundary, that may also improve efficiency if ZPL is made to do that.

Sponsored by:   iXsystems, Inc.

Authored by: Alexander Motin <mav@FreeBSD.org>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Andriy Gapon <avg@FreeBSD.org>
Reviewed by: Steven Hartland <steven.hartland@multiplay.co.uk>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Reviewed by: Richard Elling <Richard.Elling@RichardElling.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Richard Yao <ryao@gentoo.org>
Ported-by: Giuseppe Di Natale <dinatale2@llnl.gov>

OpenZFS-issue: https://www.illumos.org/issues/7578
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/aeb13ac
Closes #6191
2017-06-09 09:15:37 -07:00
.github Explain reason for Signed-off-by in CONTRIBUTING 2017-05-31 07:30:07 -07:00
cmd OpenZFS 7578 - Fix/improve some aspects of ZIL writing 2017-06-09 09:15:37 -07:00
config config: allow --with-linux without --with-linux-obj 2017-05-25 10:14:13 -07:00
contrib Fix initramfs hook for merged /usr/lib and /lib 2017-02-27 12:03:23 -08:00
etc zpool iostat/status -c improvements 2017-06-05 10:52:15 -07:00
include OpenZFS 7578 - Fix/improve some aspects of ZIL writing 2017-06-09 09:15:37 -07:00
lib Fix import finding spare/l2cache when path changes 2017-06-01 06:38:04 -07:00
man OpenZFS 7578 - Fix/improve some aspects of ZIL writing 2017-06-09 09:15:37 -07:00
module OpenZFS 7578 - Fix/improve some aspects of ZIL writing 2017-06-09 09:15:37 -07:00
rpm zpool iostat/status -c improvements 2017-06-05 10:52:15 -07:00
scripts zpool iostat/status -c improvements 2017-06-05 10:52:15 -07:00
tests Skip tests that are slow on 32-bit builders 2017-06-06 19:04:01 -07:00
udev Fix spelling 2017-01-03 11:31:18 -06:00
.gitignore Improve gitignore 2017-05-25 10:14:13 -07:00
.gitmodules Add zimport.sh compatibility test script 2014-02-21 12:10:31 -08:00
AUTHORS Add a missing > to AUTHORS 2014-09-02 14:18:53 -07:00
autogen.sh build: do not call boilerplate ourself 2013-04-02 10:55:20 -07:00
configure.ac zpool iostat/status -c improvements 2017-06-05 10:52:15 -07:00
copy-builtin Allow c99 when building ZFS in the kernel tree 2017-03-27 12:31:15 -07:00
COPYRIGHT Update ZED copyright boilerplate 2015-05-11 15:07:00 -07:00
DISCLAIMER Fix minor typos and update marketing copy. 2013-03-21 12:51:06 -07:00
Makefile.am Prebaked scripts for zpool status/iostat -c 2017-04-21 09:27:04 -07:00
META Tag 0.7.0-rc4 2017-05-05 10:33:40 -07:00
OPENSOLARIS.LICENSE Add CDDL license file 2008-12-01 14:49:34 -08:00
README.markdown Add CONTRIBUTING information and templates 2016-12-09 12:48:12 -07:00
TEST Retire filebench testing 2017-06-01 06:24:28 -07:00
zfs-script-config.sh.in zpool iostat/status -c improvements 2017-06-05 10:52:15 -07:00
zfs.release.in Move zfs.release generation to configure step 2012-07-12 12:22:51 -07:00

ZFS is an advanced file system and volume manager which was originally developed for Solaris and is now maintained by the Illumos community.

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.