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diff --git a/Documentation/config/reftable.adoc b/Documentation/config/reftable.adoc new file mode 100644 index 0000000000..57087803a5 --- /dev/null +++ b/Documentation/config/reftable.adoc @@ -0,0 +1,56 @@ +reftable.blockSize:: + The size in bytes used by the reftable backend when writing blocks. + The block size is determined by the writer, and does not have to be a + power of 2. The block size must be larger than the longest reference + name or log entry used in the repository, as references cannot span + blocks. ++ +Powers of two that are friendly to the virtual memory system or +filesystem (such as 4kB or 8kB) are recommended. Larger sizes (64kB) can +yield better compression, with a possible increased cost incurred by +readers during access. ++ +The largest block size is `16777215` bytes (15.99 MiB). The default value is +`4096` bytes (4kB). A value of `0` will use the default value. + +reftable.restartInterval:: + The interval at which to create restart points. The reftable backend + determines the restart points at file creation. Every 16 may be + more suitable for smaller block sizes (4k or 8k), every 64 for larger + block sizes (64k). ++ +More frequent restart points reduces prefix compression and increases +space consumed by the restart table, both of which increase file size. ++ +Less frequent restart points makes prefix compression more effective, +decreasing overall file size, with increased penalties for readers +walking through more records after the binary search step. ++ +A maximum of `65535` restart points per block is supported. ++ +The default value is to create restart points every 16 records. A value of `0` +will use the default value. + +reftable.indexObjects:: + Whether the reftable backend shall write object blocks. Object blocks + are a reverse mapping of object ID to the references pointing to them. ++ +The default value is `true`. + +reftable.geometricFactor:: + Whenever the reftable backend appends a new table to the stack, it + performs auto compaction to ensure that there is only a handful of + tables. The backend does this by ensuring that tables form a geometric + sequence regarding the respective sizes of each table. ++ +By default, the geometric sequence uses a factor of 2, meaning that for any +table, the next-biggest table must at least be twice as big. A maximum factor +of 256 is supported. + +reftable.lockTimeout:: + Whenever the reftable backend appends a new table to the stack, it has + to lock the central "tables.list" file before updating it. This config + controls how long the process will wait to acquire the lock in case + another process has already acquired it. Value 0 means not to retry at + all; -1 means to try indefinitely. Default is 100 (i.e., retry for + 100ms). |