Thursday Aug 29, 2013

Timezone troubles when dual booting

I have a laptop that dual boots Solaris and Windows XP. When I switched between the two OSes I would have to reset the clock because the time would be eight hours out. This has been naggging at me for a while, so I dug into what was going on.

It seems that Windows assumes that the Real-Time Clock (RTC) in the bios is using local time. So it will read the clock and display whatever time is shown there.

Solaris on the other hand assumes that the clock is in Universal Time Format (UTC), so you have to apply a time zone transformation in order to get to the local time.

Obviously, if you adjust the clock to make one correct, then the other is wrong.

To me, it seems more natural to have the clock in a laptop work on UTC - because when you travel the local time changes. There is a registry setting in Windows that, when set to 1, tells the machine to use UTC:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal

However, it has some problems and is potentially not robust over sleep. So we have to work the other way, and get Solaris to use local time. Fortunately, this is a relatively simple change running the following as root (pick the appropriate timezone for your location):

rtc -z US/Pacific

Tuesday Aug 27, 2013

My Oracle Open World and JavaOne schedule

I've got my schedule for Oracle Open World and JavaOne:

Note that on Thursday I have about 30 minutes between my two talks, so expect me to rush out of the database talk in order to get to the Java talk.

Friday Aug 09, 2013

How to use a lot of threads ....

The SPARC M5-32 has 1,536 virtual CPUs. There is a lot that you can do with that much resource and a bunch of us sat down to write a white paper discussing the options.

There are a couple of key observations in there. First of all it is quite likely that such a large system will not end up running a single instance of a single application. Therefore it is useful to understand the various options for virtualising the system. The second observation is that there are a number of details to take care of when writing an application that is expected to scale to large numbers of threads.

Anyhow, I hope you find it a useful read.

About

Darryl Gove is a senior engineer in the Solaris Studio team, working on optimising applications and benchmarks for current and future processors. He is also the author of the books:
Multicore Application Programming
Solaris Application Programming
The Developer's Edge

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