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9fa8753aa1
This is version 2 of [Omar's] XFS realtime allocator opimization patch series. Changes since v1 [1]: - Fixed potential overflow in patch 4. - Changed deprecated typedefs to normal struct names - Fixed broken indentation - Used xfs_fileoff_t instead of xfs_fsblock_t where appropriate. - Added calls to xfs_rtbuf_cache_relse anywhere that the cache is used instead of relying on the buffers being dirtied and thus attached to the transaction. - Clarified comments and commit messages in a few places. - Added Darrick's Reviewed-bys. Cover letter from v1: Our distributed storage system uses XFS's realtime device support as a way to split an XFS filesystem between an SSD and an HDD -- we configure the HDD as the realtime device so that metadata goes on the SSD and data goes on the HDD. We've been running this in production for a few years now, so we have some fairly fragmented filesystems. This has exposed various CPU inefficiencies in the realtime allocator. These became even worse when we experimented with using XFS_XFLAG_EXTSIZE to force files to be allocated contiguously. This series adds several optimizations that don't change the realtime allocator's decisions, but make them happen more efficiently, mainly by avoiding redundant work. We've tested these in production and measured ~10%% lower CPU utilization. Furthermore, it made it possible to use XFS_XFLAG_EXTSIZE to force contiguous allocations -- without these patches, our most fragmented systems would become unresponsive due to high CPU usage in the realtime allocator, but with them, CPU utilization is actually ~4-6%% lower than before, and disk I/O utilization is 15-20%% lower. Patches 2 and 3 are preparations for later optimizations; the remaining patches are the optimizations themselves. 1: https://lore.kernel.org/linux-xfs/cover.1687296675.git.osandov@osandov.com/ v2.1: djwong rebased everything atop his own cleanups, added dave's rtalloc_args v2.2: rebase with new apis and clean them up too v2.3: move struct definition around for lolz With a bit of luck, this should all go splendidly. Signed-off-by: Darrick J. Wong <djwong@kernel.org> -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQQ2qTKExjcn+O1o2YRKO3ySh0YRpgUCZTFTEQAKCRBKO3ySh0YR pkbpAQD52XiQ7GXAiZSfJDStw1cr3C664AhmX/KdGtzHPmqxIQD/e8I0u1GEPezK 6qnipiiFBq/px/hqakx5t8VgHfucwwY= =XdBg -----END PGP SIGNATURE----- Merge tag 'rtalloc-speedups-6.7_2023-10-19' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into xfs-6.7-mergeA xfs: CPU usage optimizations for realtime allocator [v2.3] This is version 2 of [Omar's] XFS realtime allocator opimization patch series. Changes since v1 [1]: - Fixed potential overflow in patch 4. - Changed deprecated typedefs to normal struct names - Fixed broken indentation - Used xfs_fileoff_t instead of xfs_fsblock_t where appropriate. - Added calls to xfs_rtbuf_cache_relse anywhere that the cache is used instead of relying on the buffers being dirtied and thus attached to the transaction. - Clarified comments and commit messages in a few places. - Added Darrick's Reviewed-bys. Cover letter from v1: Our distributed storage system uses XFS's realtime device support as a way to split an XFS filesystem between an SSD and an HDD -- we configure the HDD as the realtime device so that metadata goes on the SSD and data goes on the HDD. We've been running this in production for a few years now, so we have some fairly fragmented filesystems. This has exposed various CPU inefficiencies in the realtime allocator. These became even worse when we experimented with using XFS_XFLAG_EXTSIZE to force files to be allocated contiguously. This series adds several optimizations that don't change the realtime allocator's decisions, but make them happen more efficiently, mainly by avoiding redundant work. We've tested these in production and measured ~10%% lower CPU utilization. Furthermore, it made it possible to use XFS_XFLAG_EXTSIZE to force contiguous allocations -- without these patches, our most fragmented systems would become unresponsive due to high CPU usage in the realtime allocator, but with them, CPU utilization is actually ~4-6%% lower than before, and disk I/O utilization is 15-20%% lower. Patches 2 and 3 are preparations for later optimizations; the remaining patches are the optimizations themselves. 1: https://lore.kernel.org/linux-xfs/cover.1687296675.git.osandov@osandov.com/ v2.1: djwong rebased everything atop his own cleanups, added dave's rtalloc_args v2.2: rebase with new apis and clean them up too v2.3: move struct definition around for lolz With a bit of luck, this should all go splendidly. Signed-off-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Chandan Babu R <chandanbabu@kernel.org> * tag 'rtalloc-speedups-6.7_2023-10-19' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux: xfs: don't look for end of extent further than necessary in xfs_rtallocate_extent_near() xfs: don't try redundant allocations in xfs_rtallocate_extent_near() xfs: limit maxlen based on available space in xfs_rtallocate_extent_near() xfs: return maximum free size from xfs_rtany_summary() xfs: invert the realtime summary cache xfs: simplify rt bitmap/summary block accessor functions xfs: simplify xfs_rtbuf_get calling conventions xfs: cache last bitmap block in realtime allocator xfs: consolidate realtime allocation arguments |
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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.