Re: [PATCH 00/16] Remove hash page table slot tracking from linux PTE
From: Paul Mackerras <hidden>
Date: 2017-10-27 05:41:39
On Fri, Oct 27, 2017 at 10:57:13AM +0530, Aneesh Kumar K.V wrote:
On 10/27/2017 10:04 AM, Paul Mackerras wrote:quoted
How do we interpret these numbers? Are they times, or speed? Is larger better or worse?Sorry for not including the details. They are time in seconds. Test case is a modified mmap_bench included in powerpc/selftest.quoted
Can you give us the mean and standard deviation for each set of 5 please?powernv without patch median= 51.432255 stdev = 0.370835 with patch median = 50.739922 stdev = 0.06419662 pseries without patch median = 116.617884 stdev = 3.04531023 with patch no hcall median = 119.42494 stdev = 0.85874552 with patch and hcall median = 117.735808 stdev = 2.7624151
So on powernv, the patch set *improves* performance by about 1.3% (almost 2 standard deviations). Do we know why that is? On pseries, performance is about 2.4% worse without new hcalls, but that is less than 1 standard deviation. With new hcalls, performance is 0.95% worse, only a third of a standard deviation. I think we need to do more measurements to try to get a more accurate picture here. Were the pseries numbers done on KVM or PowerVM? Could you do a set of measurements on the other one too please? (I assume the numbers with the new hcall were done on KVM, and can't be done on PowerVM.) Paul.