woonhak/ermia

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. Install from your favorite package manager. ERMIA uses mmap with MAP_HUGETLB to allocate huge pages. MAP_HUGETLB is available after Linux 2.6.32.
Make sure you have enough huge pages. Almost all memory allocations come from the space carved out here. Assuming 2MB pages, the command below will allocate 40GB of memory:

sudo sh -c 'echo [x pages] > /proc/sys/vm/nr_hugepages'

This limits the maximum for --node-memory-gb to 10 for a 4-socket machine (see below).

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

SSI and SSN are mutually exclusive.

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

Adjust maximum concurrent workers

By default we support up to 256 cores. The limit can be adjusted by setting MAX_THREADS defined under config in dbcore/sm-config.h. MAX_THREADS must be a multiple of 64.

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] \
       [scale-factor] \
       [num-threads] \
       [duration (seconds)] \
       "[other system-wide runtime options]" \
       "[other benchmark-specific runtime options]"`

Note the quotation marks for additional options.

System-wide runtime options

--node-memory-gb: how many GBs of memory to allocate per socket.

--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.

--phantom-prot: enable phantom protection.

--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.

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.

woonhak / ermia