mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-28 14:44:10 +08:00
adb86dbe42
Currently when reserving space for deleting the csum items for a data extent, when adding or updating a delayed ref head, we determine how many leaves of csum items we can have and then pass that number to the helper btrfs_calc_delayed_ref_bytes(). This helper is used for calculating space for all tree modifications we need when running delayed references, however the amount of space it computes is excessive for deleting csum items because: 1) It uses btrfs_calc_insert_metadata_size() which is excessive because we only need to delete csum items from the csum tree, we don't need to insert any items, so btrfs_calc_metadata_size() is all we need (as it computes space needed to delete an item); 2) If the free space tree is enabled, it doubles the amount of space, which is pointless for csum deletion since we don't need to touch the free space tree or any other tree other than the csum tree. So improve on this by tracking how many csum deletions we have and using a new helper to calculate space for csum deletions (just a wrapper around btrfs_calc_metadata_size() with a comment). This reduces the amount of space we need to reserve for csum deletions by a factor of 4, and it helps reduce the number of times we have to block space reservations and have the reclaim task enter the space flushing algorithm (flush delayed items, flush delayed refs, etc) in order to satisfy tickets. For example this results in a total time decrease when unlinking (or truncating) files with many extents, as we end up having to block on space metadata reservations less often. Example test: $ cat test.sh #!/bin/bash DEV=/dev/nullb0 MNT=/mnt/test umount $DEV &> /dev/null mkfs.btrfs -f $DEV # Use compression to quickly create files with a lot of extents # (each with a size of 128K). mount -o compress=lzo $DEV $MNT # 100G gives at least 983040 extents with a size of 128K. xfs_io -f -c "pwrite -S 0xab -b 1M 0 120G" $MNT/foobar # Flush all delalloc and clear all metadata from memory. umount $MNT mount -o compress=lzo $DEV $MNT start=$(date +%s%N) rm -f $MNT/foobar end=$(date +%s%N) dur=$(( (end - start) / 1000000 )) echo "rm took $dur milliseconds" umount $MNT Before this change rm took: 7504 milliseconds After this change rm took: 6574 milliseconds (-12.4%) Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| 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.