On Tue, Jun 20, 2023 at 02:32:10PM -0700, Omar Sandoval wrote: > Hello, > > 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. > > This is based on Linus' tree as of today (commit > 692b7dc87ca6d55ab254f8259e6f970171dc9d01). > > Thanks! > > Omar Sandoval (6): > xfs: cache last bitmap block in realtime allocator > xfs: invert the realtime summary cache > xfs: return maximum free size from xfs_rtany_summary() > xfs: limit maxlen based on available space in > xfs_rtallocate_extent_near() > xfs: don't try redundant allocations in xfs_rtallocate_extent_near() > xfs: don't look for end of extent further than necessary in > xfs_rtallocate_extent_near() > > fs/xfs/libxfs/xfs_rtbitmap.c | 173 ++++++++++++++-------------- > fs/xfs/xfs_mount.h | 6 +- > fs/xfs/xfs_rtalloc.c | 215 ++++++++++++++++------------------- > fs/xfs/xfs_rtalloc.h | 28 +++-- > 4 files changed, 207 insertions(+), 215 deletions(-) Gentle ping.
