From 119e9db233ad0f4cbd4cfb9f9385a7bca378b37d Mon Sep 17 00:00:00 2001 From: Zeng Chi Date: Mon, 21 Sep 2026 18:24:42 +0800 Subject: KVM: Don't pre-reserve xarray entries when storing empty/NULL attributes Skip the xarray reservation loop when clearing all memory attributes, as storing NULL only erases the entry and never needs to allocate, so no reservation (and no cleanup of a failed one) is required in that case. Suggested-by: Sean Christopherson Cc: David Ballesteros Signed-off-by: Zeng Chi Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com [sean: split to separate patch] Signed-off-by: Sean Christopherson --- Documentation/ABI/testing/sysfs-block-bcache | 149 +++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-block-bcache (limited to 'Documentation/ABI/testing/sysfs-block-bcache') diff --git a/Documentation/ABI/testing/sysfs-block-bcache b/Documentation/ABI/testing/sysfs-block-bcache new file mode 100644 index 000000000..9344a657c --- /dev/null +++ b/Documentation/ABI/testing/sysfs-block-bcache @@ -0,0 +1,149 @@ +What: /sys/block//bcache/unregister +Date: November 2010 +Contact: Kent Overstreet +Description: + A write to this file causes the backing device or cache to be + unregistered. If a backing device had dirty data in the cache, + writeback mode is automatically disabled and all dirty data is + flushed before the device is unregistered. Caches unregister + all associated backing devices before unregistering themselves. + +What: /sys/block//bcache/clear_stats +Date: November 2010 +Contact: Kent Overstreet +Description: + Writing to this file resets all the statistics for the device. + +What: /sys/block//bcache/cache +Date: November 2010 +Contact: Kent Overstreet +Description: + For a backing device that has cache, a symlink to + the bcache/ dir of that cache. + +What: /sys/block//bcache/cache_hits +Date: November 2010 +Contact: Kent Overstreet +Description: + For backing devices: integer number of full cache hits, + counted per bio. A partial cache hit counts as a miss. + +What: /sys/block//bcache/cache_misses +Date: November 2010 +Contact: Kent Overstreet +Description: + For backing devices: integer number of cache misses. + +What: /sys/block//bcache/cache_hit_ratio +Date: November 2010 +Contact: Kent Overstreet +Description: + For backing devices: cache hits as a percentage. + +What: /sys/block//bcache/sequential_cutoff +Date: November 2010 +Contact: Kent Overstreet +Description: + For backing devices: Threshold past which sequential IO will + skip the cache. Read and written as bytes in human readable + units (i.e. echo 10M > sequntial_cutoff). + +What: /sys/block//bcache/bypassed +Date: November 2010 +Contact: Kent Overstreet +Description: + Sum of all reads and writes that have bypassed the cache (due + to the sequential cutoff). Expressed as bytes in human + readable units. + +What: /sys/block//bcache/writeback +Date: November 2010 +Contact: Kent Overstreet +Description: + For backing devices: When on, writeback caching is enabled and + writes will be buffered in the cache. When off, caching is in + writethrough mode; reads and writes will be added to the + cache but no write buffering will take place. + +What: /sys/block//bcache/writeback_running +Date: November 2010 +Contact: Kent Overstreet +Description: + For backing devices: when off, dirty data will not be written + from the cache to the backing device. The cache will still be + used to buffer writes until it is mostly full, at which point + writes transparently revert to writethrough mode. Intended only + for benchmarking/testing. + +What: /sys/block//bcache/writeback_delay +Date: November 2010 +Contact: Kent Overstreet +Description: + For backing devices: In writeback mode, when dirty data is + written to the cache and the cache held no dirty data for that + backing device, writeback from cache to backing device starts + after this delay, expressed as an integer number of seconds. + +What: /sys/block//bcache/writeback_percent +Date: November 2010 +Contact: Kent Overstreet +Description: + For backing devices: If nonzero, writeback from cache to + backing device only takes place when more than this percentage + of the cache is used, allowing more write coalescing to take + place and reducing total number of writes sent to the backing + device. Integer between 0 and 40. + +What: /sys/block//bcache/synchronous +Date: November 2010 +Contact: Kent Overstreet +Description: + For a cache, a boolean that allows synchronous mode to be + switched on and off. In synchronous mode all writes are ordered + such that the cache can reliably recover from unclean shutdown; + if disabled bcache will not generally wait for writes to + complete but if the cache is not shut down cleanly all data + will be discarded from the cache. Should not be turned off with + writeback caching enabled. + +What: /sys/block//bcache/bucket_size +Date: November 2010 +Contact: Kent Overstreet +Description: + For a cache, bucket size in human readable units, as set at + cache creation time; should match the erase block size of the + SSD for optimal performance. + +What: /sys/block//bcache/nbuckets +Date: November 2010 +Contact: Kent Overstreet +Description: + For a cache, the number of usable buckets. + +What: /sys/block//bcache/tree_depth +Date: November 2010 +Contact: Kent Overstreet +Description: + For a cache, height of the btree excluding leaf nodes (i.e. a + one node tree will have a depth of 0). + +What: /sys/block//bcache/btree_cache_size +Date: November 2010 +Contact: Kent Overstreet +Description: + Number of btree buckets/nodes that are currently cached in + memory; cache dynamically grows and shrinks in response to + memory pressure from the rest of the system. + +What: /sys/block//bcache/written +Date: November 2010 +Contact: Kent Overstreet +Description: + For a cache, total amount of data in human readable units + written to the cache, excluding all metadata. + +What: /sys/block//bcache/btree_written +Date: November 2010 +Contact: Kent Overstreet +Description: + For a cache, sum of all btree writes in human readable units. -- cgit v1.3.1