This makes is much easier to process on the server and opens new
optimization possibilities. It also fixes theoretical problems, which
may be caused by invalid ordering of events with the same timestamp.
This change exploits the fact that events are processed in batches
originating from a single thread. A single message changing thread
context is enough to handle multiple messages, as opposed to inclusion
of thread identifier in each message.
There shouldn't be any changes in generated code on modern
architectures, as the memcpy will be reduced to a store/load operation
identical to the one generated with plain struct member access.
GetTime( cpu ) needs special handling, as the MSVC intrinsic for rdtscp
can't store cpu identifier in a register. Using intermediate variable
would cause store to stack, read from stack, store to the destination
address. Since rdtscp is only available on x86, which handles unaligned
stores without any problems, we can have one place with direct struct
member access.
Source file, function name and line number are now stored in a const
static container object. This has the following benefits:
- Slightly lighter profiling workload (3 instructions less).
- Profiling queue event size is significantly reduced, by 12 bytes. This
has an effect on all queue event types.
- Source location grouping has now no cost, as it's performed at the
compilation stage. This allows simplification of server code.
The downside is that the full source location resolution is now
performed in two steps, as the server has to query both source location
container and strings contained within. This has almost no real impact
on profiler operation.
