On Wed, 08 Oct, at 11:51:09AM, Peter Zijlstra wrote: > On Wed, Sep 24, 2014 at 03:04:13PM +0100, Matt Fleming wrote: > > From: Matt Fleming <[email protected]> > > > > It's possible to run into issues with re-using unused monitoring IDs > > because there may be stale cachelines associated with that ID from a > > previous allocation. This can cause the LLC occupancy values to be > > inaccurate. > > > > To attempt to mitigate this problem we place the IDs on a least recently > > used list, essentially a FIFO. The basic idea is that the longer the > > time period between ID re-use the lower the probability that stale > > cachelines exist in the cache. > > Do we want to provide a user configurable minumum guaranteed queue time?
Potentially, yeah. That might be better suited as part of the final patch that includes the rotation code, which already has a delayed workqueue. We could add a minimum queue time before we start querying whether the data occupancy value for an RMID has dropped to zero on all sockets. That'd save us from an expensive smp_call_function_many() when we're unlikely to succeed anyway. -- Matt Fleming, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
