improving replay performance

Robert O'Callahan robert at
Fri Nov 20 23:06:45 UTC 2015

On Sat, Nov 21, 2015 at 12:00 PM, Chris Jones <jones.chris.g at>

> On Thu, Nov 19, 2015 at 6:32 PM, Robert O'Callahan <robert at>
> wrote:
>> * After we've replayed a set of buffered syscalls, we need to induce a
>> ptrace stop so that rr can regain control and begin replaying the following
>> event. I've thought of many ways to do this, none of which are wholly
>> satisfying.
> ​I don't quite understand the problem here ... since the buffer flush
> (virtual event) was triggered by the next (real) event, can't we just
> discard the buffer flush event after restoring the saved data and start
> replaying the next one?​

In most cases, yes, but sometimes after flushing the last event we need to
set the notify_on_syscall_hook_exit flag.

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