Fix async_io regression in scans (#10939)

Summary:
Fix async_io regression in scans due to incorrect check which was causing the valid data in buffer to be cleared during seek.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10939

Test Plan:
- stress tests  export CRASH_TEST_EXT_ARGS="--async_io=1"
    make crash_test -j32
- Ran db_bench command which was caught the regression:
./db_bench --db=/rocksdb_async_io_testing/prefix_scan --disable_wal=1 --use_existing_db=true --benchmarks="seekrandom" -key_size=32 -value_size=512 -num=50000000 -use_direct_reads=false -seek_nexts=963 -duration=30 -ops_between_duration_checks=1 --async_io=true --compaction_readahead_size=4194304 --log_readahead_size=0 --blob_compaction_readahead_size=0 --initial_auto_readahead_size=65536 --num_file_reads_for_auto_readahead=0 --max_auto_readahead_size=524288

seekrandom   :    3777.415 micros/op 264 ops/sec 30.000 seconds 7942 operations;  132.3 MB/s (7942 of 7942 found)

Reviewed By: anand1976

Differential Revision: D41173899

Pulled By: akankshamahajan15

fbshipit-source-id: 2d75b06457d65b1851c92382565d9c3fac329dfe

diff --git a/HISTORY.md b/HISTORY.md
index 207d22f26f13b6978e5aacd45d5524496b81a0c0..439223c2aeddd13f8bae66af55186451955393dd 100644 (file)
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -8,6 +8,7 @@
 * Fix memory corruption error in scans if async_io is enabled. Memory corruption happened if there is IOError while reading the data leading to empty buffer and other buffer already in progress of async read goes again for reading.
 * Fix failed memtable flush retry bug that could cause wrongly ordered updates, which would surface to writers as `Status::Corruption` in case of `force_consistency_checks=true` (default). It affects use cases that enable both parallel flush (`max_background_flushes > 1` or `max_background_jobs >= 8`) and non-default memtable count (`max_write_buffer_number > 2`).
 * Fixed an issue where the `READ_NUM_MERGE_OPERANDS` ticker was not updated when the base key-value or tombstone was read from an SST file.
+* Fixed a regression in scan for async_io. During seek, valid buffers were getting cleared causing a regression.
 
 ### New Features
 * Add basic support for user-defined timestamp to Merge (#10819).

diff --git a/file/file_prefetch_buffer.cc b/file/file_prefetch_buffer.cc
index 9222acdfa7a8197621390dd192b2a1c745226e16..9ea9129e2dacb044020e27d104d15fb4f46c5c47 100644 (file)
--- a/file/file_prefetch_buffer.cc
+++ b/file/file_prefetch_buffer.cc
@@ -664,7 +664,7 @@ bool FilePrefetchBuffer::TryReadFromCacheAsync(
     // submitted in PrefetchAsync should match with this request. Otherwise
     // buffers will be outdated.
     // Random offset called. So abort the IOs.
-    if (bufs_[curr_].offset_ != offset) {
+    if (prev_offset_ != offset) {
       AbortAllIOs();
       bufs_[curr_].buffer_.Clear();
       bufs_[curr_ ^ 1].buffer_.Clear();