ermia: A C++ repository from theopengroup

ERMIA

Fast and Robust OLTP using Epoch-based Resource Management and Indirection Array

For more information, you may refer to our SIGMOD'16 paper (https://github.com/ermia-db/ermia/raw/master/ermia.pdf)

Environment configurations

Software dependencies: libnuma and tcmalloc (part of google perftools). Install from your favorite package manager.
mlock limits. Add the following to /etc/security/limits.conf (replace "[user]" with your login):

[user] soft memlock unlimited
[user] hard memlock unlimited

Re-login to apply.

Choosing a CC scheme

ERMIA supports Read Committed (RC), Snapshot Isolation (SI), Serializable Snapshot Isolation (SSI), and Serial Safety Net (SSN) with SI/RC. Switches are defined in src/macros.h:

#define USE_PARALLEL_SSI to use serializable snapshot isolation (SSI);
#define USE_PARALLEL_SSN to use the serial safety net (SSN);
- SSN may be used in conjunction with RC (USE_READ_COMMITTED) or SI (default);
- # define DO_EARLY_SSN_CHECKS enables SSN window exclusion tests during normal reads and writes.

USE_PARALLEL_SSI and USE_PARALLEL_SSN are mutually exclusive.

Giving -D[SCHEME] to $make also works. SCHEME can be RC, SI, RC_SSN, SI_SSN, or SSI.

Build it

Use src/build.sh to compile ERMIA. For performance runs, $ build.sh, $ build.sh 1 for debugging.

Run it

$run.sh \
       [executable] \
       [benchmark] \
       [num-threads] \
       [duration (seconds)] \
       "[other system-wide runtime options]" \
       "[other benchmark-specific runtime options]"`

Note the quotation marks for additional options. Currently we support up to 64 threads, supporting more is in-progress.

System-wide runtime options

--prefault-gig: how many GBs of memory to prefault upon start.

--null-log-device: flush log buffer to /dev/null. With more than 30 threads, log flush (even to tmpfs) can easily become a bottleneck because of a mutex in the kernel held during the flush. This option does not disable logging, but it voids the ability to recover.

--tmpfs-dir: location of the log buffer's mmap file. Default: /tmpfs/.

--enable-gc: turn on garbage collection. Currently there is only one GC thread.

--enable-chkpt: enable checkpointing.

--warm-up: strategy to load versions upon recovery. Candidates are:

eager: load all latest versions during recovery, so the database is fully in-memory when it starts to process new transactions;
lazy: start a thread to load versions in the background after recovery, so the database is partially in-memory when it starts to process new transactions.
none: load versions on-demand upon access (anti-caching).

SSI and SSN specific:

--safesnap: enable safe snapshot for read-only transactions.

SSN-specific:

--ssn-read-opt-threshold: versions that are read by a read-mostly transaction and older than this value are considered "old" and will not be tracked; setting it to 0 will skip all read tracking for read-mostly transactions (TXN_FLAG_READ_MOSTLY).

SSI-specific: --ssi-read-only-opt: enable P&G style read-only optimization for SSI.