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Create a new xrep_newbt structure to encapsulate a fake root for creating a staged btree cursor as well as to track all the blocks that we need to reserve in order to build that btree. As for the particular choice of lowspace thresholds and btree block slack factors -- at this point one could say that the thresholds in online repair come from bulkload_estimate_ag_slack in xfs_repair[1]. But that's not the entire story, since the offline btree rebuilding code in xfs_repair was merged as a retroport of the online btree code in this patchset! Before xfs_btree_staging.[ch] came along, xfs_repair determined the slack factor (aka the number of slots to leave unfilled in each new btree block) via open-coded logic in repair/phase5.c[2]. At that point the slack factors were arbitrary quantities per btree. The rmapbt automatically left 10 slots free; everything else left zero. That had a noticeable effect on performance straight after mounting because adding records to /any/ btree would result in splits. A few years ago when this patch was first written, Dave and I decided that repair should generate btree blocks that were 75% full unless space was tight, in which case it should try to fill the blocks to nearly full. We defined tight as ~10% free to avoid repair failures but settled on 3/32 (~9%) to avoid div64. IOWs, we mostly pulled the thresholds out of thin air. We've been QAing with those geometry numbers ever since. ;) Link: https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git/tree/repair/bulkload.c?h=v6.5.0#n114 Link: https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git/tree/repair/phase5.c?h=v4.19.0#n1349 Signed-off-by: Darrick J. Wong <djwong@kernel.org> Reviewed-by: Dave Chinner <dchinner@redhat.com> |
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| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
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| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
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| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.