Re: [ofa-general] Re: [GIT PULL] please pull ummunotify

Roland Dreier
2009-09-30T17:06:32Z

> Performance events filtering is being worked on and now with the proper
> non-DoS limit you've added you can lose events too, dont you? So it's
> all a question of how much buffering to add - and with perf events too
> you can buffer arbitrary large amount of events.

No, the idea for non-DoS for ummunotify is that we would limit the
number of regions the application can register; so an application might
hit the limit up front but no runtime loss of events once a region was
registered successfully.

> I think this could be done in a simpler, less limited, more generic,
> more useful form by using some variation of perf events.
>
> You should be able to get all that you want by adding two TRACE_EVENT()
> tracepoints and using the existing perf event syscall to get the events
> to user-space.

Yes, I would like to use perf events too. Would it be plausible to
create a way for userspace to create a "counter" for each address range
being watched? Then events would not be lost, because those counters
would become non-zero.

> Meaning that this:
> 9 files changed, 1060 insertions(+), 1 deletions(-)

Note that lots/ of the files touched here are in Documentation or are
one-line changes to Makefiles etc.

- R.