On Fri, Jan 09, 2015 at 12:55:07PM +0000, Matt Fleming wrote: > On Wed, 07 Jan, at 01:16:17PM, Peter Zijlstra wrote: > > On Fri, Nov 14, 2014 at 09:15:11PM +0000, Matt Fleming wrote: > > + /* > > > + * A reasonable upper limit on the max threshold is the number > > > + * of lines tagged per RMID if all RMIDs have the same number of > > > + * lines tagged in the LLC. > > > + * > > > + * For a 35MB LLC and 56 RMIDs, this is ~1.8% of the LLC. > > > + */ > > > + __intel_cqm_max_threshold = > > > + boot_cpu_data.x86_cache_size * 1024 / (cqm_max_rmid + 1); > > > > Seeing how a percentage is without unit, the 35MB figure seems > > pointless. > > It's only an example to demonstrate that this fudge calculation makes > sense on the current class of CQM-enabled hardware. > > > Also, why would a flat distribution be a good measure for 'empty'? I > > would think that would in fact constitute in use. > > It's not, it's a good measure for 'full'. This is the *max* threshold. > When searching for RMIDs to stabilize we'll stop searching if > __intel_cqm_threshold == __intel_cqm_max_threshold, since that indicates > all our RMIDs have *so* many lines tagged that it's unlikely increasing > __intel_cqm_threshold any further would be a win.
Right, but we'll also consider RMIDs with less than this as fit for reuse. So we'll re-use RMIDs that are effectively full. Our aim is to acquire an 'empty' RMID, not give up and start reusing full ones just because, right? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
