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Fix bug in MultiRead() coalescing introduced in 4fc216649d (#6446). (#6979)

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Summary:
TryMerge() overzealously creates one huge file read request in an attempt to merge smaller disjoint requests. For example, ~30 input requests of ~100 bytes output as 1 request of 100 MiB causing alarmingly large read throughputs to be repeatedly observed by the environment.

Signed-off-by: Jason Volk <jason@zemos.net>

Pull Request resolved: https://github.com/facebook/rocksdb/pull/6979

Reviewed By: siying

Differential Revision: D22668892

Pulled By: cheng-chang

fbshipit-source-id: 7506fe9621b7f1a747dadf6b8ddb1b1a141c1937
This commit is contained in:
Jason Volk 2020-07-22 15:02:10 -07:00 committed by Facebook GitHub Bot
parent 96ce0470a7
commit 4a60cb20ad
1 changed files with 1 additions and 1 deletions
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2
file/random_access_file_reader.cc
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@ -194,7 +194,7 @@ bool TryMerge(FSReadRequest* dest, const FSReadRequest& src) {
size_t src_offset = static_cast<size_t>(src.offset);
size_t dest_end = End(*dest);
size_t src_end = End(src);
if (std::max(dest_offset, dest_offset) > std::min(dest_end, src_end)) {
if (std::max(dest_offset, src_offset) > std::min(dest_end, src_end)) {
return false;
}
dest->offset = static_cast<uint64_t>(std::min(dest_offset, src_offset));