Changeset 53058 in vbox

Timestamp:

Oct 14, 2014 4:02:14 PM (10 years ago)

Author:

vboxsync

Message:

HostDrivers/support: comment.

File:

trunk/src/VBox/HostDrivers/Support/SUPDrv.c

-              r53054
+              r53058
  * @remarks Measuring TSC deltas between the CPUs is tricky because we need to
  *     read the TSC at exactly the same time on both the master and the worker
+ *     CPUs. Due to DMA, bus arbitration, cache locality, contention, pipelining
+ *     etc. there is no guaranteed way of doing this on x86 CPUs. We try to
+ *     minimize the measurement error by computing the minimum read time of the
+ *     compare statement in the worker by taking TSC measurements across it.
+ *     CPUs. Due to DMA, bus arbitration, cache locality, contention, SMI,
+ *     pipelining etc. there is no guaranteed way of doing this on x86 CPUs. We
+ *     try to minimize the measurement error by computing the minimum read time
+ *     of the compare statement in the worker by taking TSC measurements across
+ *     it.
+ *
  *     We ignore the first few runs of the loop in order to prime the cache.

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