swh:1:snp:5115096b921df712aeb2a08114fede57fb3331fb
Revision fea2b1dfb2c554a5394e213b101516a311142fa9 authored by Andrew Kryczka on 01 June 2018, 23:46:32 UTC, committed by Facebook Github Bot on 01 June 2018, 23:57:58 UTC
Summary: For iterator reads, a `SuperVersion` is pinned to preserve a snapshot of SST files, and `Block`s are pinned to allow `key()` and `value()` to return pointers directly into a RocksDB memory region. This works for both non-mmap reads, where the block owns the memory region, and mmap reads, where the file owns the memory region. For point reads with `PinnableSlice`, only the `Block` object is pinned. This works for non-mmap reads because the block owns the memory region, so even if the file is deleted after compaction, the memory region survives. However, for mmap reads, file deletion causes the memory region to which the `PinnableSlice` refers to be unmapped. The result is usually a segfault upon accessing the `PinnableSlice`, although sometimes it returned wrong results (I repro'd this a bunch of times with `db_stress`). This PR copies the value into the `PinnableSlice` when it comes from mmap'd memory. We can tell whether the `Block` owns its memory using `Block::cachable()`, which is unset when reads do not use the provided buffer as is the case with mmap file reads. When that is false we ensure the result of `Get()` is copied. This feels like a short-term solution as ideally we'd have the `PinnableSlice` pin the mmap'd memory so we can do zero-copy reads. It seemed hard so I chose this approach to fix correctness in the meantime. Closes https://github.com/facebook/rocksdb/pull/3881 Differential Revision: D8076288 Pulled By: ajkr fbshipit-source-id: 31d78ec010198723522323dbc6ea325122a46b08
1 parent 88c3ee2
Tip revision: 19076c95aa2bcee55c26fcf0960cc844ad86ee9c authored by Levi Tamasi on 21 January 2021, 22:18:25 UTC
Update HISTORY.md for PR 7888 (#7890)
Update HISTORY.md for PR 7888 (#7890)
Tip revision: 19076c9
File | Mode | Size |
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buckifier | ||
build_tools | ||
cache | ||
cmake | ||
coverage | ||
db | ||
docs | ||
env | ||
examples | ||
hdfs | ||
include | ||
java | ||
memtable | ||
monitoring | ||
options | ||
port | ||
table | ||
third-party | ||
tools | ||
util | ||
utilities | ||
.clang-format | -rw-r--r-- | 138 bytes |
.gitignore | -rw-r--r-- | 705 bytes |
.travis.yml | -rw-r--r-- | 3.2 KB |
AUTHORS | -rw-r--r-- | 322 bytes |
CMakeLists.txt | -rw-r--r-- | 35.3 KB |
CODE_OF_CONDUCT.md | -rw-r--r-- | 249 bytes |
CONTRIBUTING.md | -rw-r--r-- | 706 bytes |
COPYING | -rw-r--r-- | 17.7 KB |
DEFAULT_OPTIONS_HISTORY.md | -rw-r--r-- | 1.5 KB |
DUMP_FORMAT.md | -rw-r--r-- | 763 bytes |
HISTORY.md | -rw-r--r-- | 61.1 KB |
INSTALL.md | -rw-r--r-- | 7.4 KB |
LANGUAGE-BINDINGS.md | -rw-r--r-- | 904 bytes |
LICENSE.Apache | -rw-r--r-- | 11.1 KB |
LICENSE.leveldb | -rw-r--r-- | 1.5 KB |
Makefile | -rw-r--r-- | 64.4 KB |
README.md | -rw-r--r-- | 1.8 KB |
ROCKSDB_LITE.md | -rw-r--r-- | 1.0 KB |
TARGETS | -rw-r--r-- | 26.9 KB |
USERS.md | -rw-r--r-- | 5.3 KB |
Vagrantfile | -rw-r--r-- | 1017 bytes |
WINDOWS_PORT.md | -rw-r--r-- | 12.5 KB |
appveyor.yml | -rw-r--r-- | 428 bytes |
issue_template.md | -rw-r--r-- | 243 bytes |
src.mk | -rw-r--r-- | 29.4 KB |
thirdparty.inc | -rw-r--r-- | 6.4 KB |
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