[lldb-dev] RFC: Processor Trace Support in LLDB

Pavel Labath via lldb-dev lldb-dev at lists.llvm.org
Fri Oct 2 03:51:06 PDT 2020

On 01/10/2020 22:32, Walter wrote:
> After a chat with Greg, we agreed on this set of commands
> trace load /path/to/json process trace start/stop process trace save
> /path/to/json thread trace start/stop thread trace dump [instructions |
> functions]

Thanks. The new commands look good to me.

The multi-process trace concept is interesting. I don't question its
usefulness -- I am sure it can be useful for various kinds of analysis
(though I've never used that myself). I am wondering though about how to
represent this thing in lldb, as we don't really have anything close to
the concept of "debugging" all processes on a given system.

The only thing that comes close is probably the kernel-level debugging.
One idea (which has just occurred to me, so it may not be good) might be
to make these traces behave similarly to that. I.e., create a single
target/process with one "thread" per physical cpu, and then have a
special "os plugin" like thing which would present individual

That would have the advantage of maintaining the one trace-one target
invariant and also would preserve the information about relative timings
of individual "processes". I think that wuold be an interesting way to
view these things, but I don't know if it would be the best one...


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