G
George Potemkin
Guest
Customer moves their databases from CentOS 6 to CentOS 7 (3.10.0-957.27.2). Both are VMWare on the same metal box. Network driver vmxnet3 Performance dropped down approximately by 9 times Test against the sports2000 database: ETIME(TRUE). FOR EACH OrderLine NO-LOCK /*NO-PREFETCH*/ /* SHARE-LOCK */ : ACCUMULATE "rec":U (COUNT). END. MESSAGE ETIME VIEW-AS ALERT-BOX. Table OrderLine has 13970 records. Results: CentOS 6 Run NO-LOCK NO-PREFETCH SHARE-LOCK 1 79 1353 1736 2 75 1364 1624 3 80 1368 2049 4 80 1328 1729 5 93 1508 1683 6 79 1368 2015 7 99 1550 1730 8 73 3714 1924 9 93 1643 1668 10 90 1426 1679 11 87 1392 1809 AVE 84.4 1637.6 1786.0 CentOS 7 Run NO-LOCK NO-PREFETCH SHARE-LOCK 1 88 7137 26541 2 102 6281 26013 3 87 7259 25303 4 82 7381 25318 5 88 6883 27381 6 84 6472 27532 7 79 6101 25775 8 87 5960 27045 9 82 6029 25494 10 111 4909 26087 11 80 6284 26263 AVE 88.2 6426.9 26250.2 Results on CentOS 6 are expected: NO-LOCK is 20 times faster than NO-LOCK NO-PREFETCH (-Mm 16384): a few messages vs. one tiny record (43 bytes in average) per network message; SHARE-LOCK is just a bit slower than NO-LOCK NO-PREFETCH. It’s still one record per network message. Results on CentOS 7: NO-LOCK is as fast as on CentOS 6; NO-LOCK NO-PREFETCH is 3.92 times slower than the same code on CentOS 6; SHARE-LOCK is 4.08 times slower than NO-LOCK NO-PREFETCH. Note: the factor 4 in both two unexpected cases. It was suggested to run ‘rngd -r /dev/urandom’ but the customer can’t find the rngd on both CentOS. What is the root case of the slowness? How to solve the issue?
Continue reading...
Continue reading...