<Oliver.Kowalke@qimonda.com> wrote in news:B1EAFF2DAE7658488B631F25813CD91F0137D996@drsse602.eu.infineon.com:
How useful can seed using MAC address + time be in system with multiple cores? Shouldn't it be CoreID + time? Just image you have 16 cores and just one MAC address. Is such an assumption valid to make?
You would need process/thread number + mac address + time
Hmm - the RFC 4122 doesn't tell anything about threads.
This is not exactly true. The first step in their basic algorithm (4.2.1) is to obtain a system-wide global lock. This lock ensures that each guid has a different time stamp. Often an implementation strays from the standard by adding in a process/thread/core number to avoid a global lock. It also talks about an optimization (in 4.2.1.4) that allocates a block of time stamps at a time and a per-process generator can allocate from that block until it is exhausted.
Version 1 UUIDs are generated according to the following algorithm:
o Determine the values for the UTC-based timestamp and clock sequence to be used in the UUID, as described in Section 4.2.1.
< snip >
Oliver
Andy.