Memristor

The Machine HP Talk November 1014
HP's datacenter scale computer

How will memristors change everything
Finding the Missing Memristor talk

GUPS - giga-updates per second
TEPS - traversed edges per second

Comments

Post a Comment

Popular posts from this blog

Oracle JDBC ReadTimeout QueryTimeout

If a query exceeds the oracle.jdbc.ReadTimeout without receiving any data, an exception is thrown and the connection is terminated by the Oracle driver on the client. Unfortunately the session will still be queued on the database and continue to wait for locks, hold any current locks, and complete any DML/PL*SQL procedures that are pending on the server-side of the orphaned connection. If an application, on a another connection, due to ReadTimeout exception, retries DML/PL*SQL  which requires locks, those queries will queue behind the initial DML/PL*SQL. This will increase the workload exacerbating the situation. On applications with retries, this can be observed by querying the v$session table  or gv$session on RAC and noting new sessions started periodically based on the ReadTimeout interval. The sessions may often have the same SQL_ID and/or SQL_HASH_VALUE. If stmt.setQueryTimeout(Seconds) is issued and the statement exceeds the timeout, it will atte...
Read more

Locks held on Oracle for hours after sessions abnormally terminated by node failure

If a session holds db locks and is abnormally terminated (no fin/ack), the locks will persist until the db session is closed, typically around 2 hours and 12 minutes with default network tcp_keepalive settings. Abnormally terminated does not include CTRL C or kill -9. The ojdbc6 driver apparently has a shutdown hook thread that closes the connections in graceful shutdowns. The OS apparently closes the connections when processes are killed. Abnormally terminated might include power failure, firewall failures, Out Of Memory, OS/kernel crash, network connection failure, JBoss or other server node failure, etc. This was easily reproduced by creating a  process that connected to the db and updated a record but did not commit. While the first process was waiting, a second process with a contending update was started which blocked on the first update. The first clients network cable was then disconnected. The second clients transaction waited for approximately 2 hours until the databa...
Read more

ActiveMQ https

ActiveMQ supports tunneling JMS over https to transparently traverse firewalls, but the  documentation  doesn't indicate how to configure it and relevant examples were lacking via google. After hacking for half a day I finally stumbled upon the simple solution. Keep in mind that you will want to create you own keys and certificate. For testing I just used the ones provided in the activemq/conf dir. Simply configure an https transport connector in conf/activemq.xml and pass the keystore, password, and truststore to activemq when started. conf/activemq.xml <amq:transportconnector uri="https://0.0.0.0:61684"> activemq start parameters -Djavax.net.ssl.keyStore=/path/activemq/conf/broker.ks -Djavax.net.ssl.keyStorePassword=password -Djavax.net.ssl.trustStore=/path/activemq/conf/broker.ts import self-signed cert into client jdk keystore cd /path/jdk1.7.0_15/jre/lib/security keytool -import -trustcacerts -file /path/activemq/conf/broker-l...
Read more