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)
- Software dependencies:
libnuma
. Install from your favorite package manager. ERMIA usesmmap
withMAP_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.
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.
- SSN may be used in conjunction with RC (
SSI
and SSN
are mutually exclusive.
Giving -D[SCHEME]
to $make
also works. SCHEME
can be RC
, SI
, RC_SSN
, SI_SSN
, or SSI
.
By default we support up to 256 cores. The limit can be adjusted by setting MAX_THREADS
defined under sysconf
in dbcore/sm-config.h.
MAX_THREADS
must be a multiple of 64.
Use src/build.sh
to compile ERMIA. For performance runs, $ build.sh
, $ build.sh 1
for debugging.
$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.
--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.
--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.