On 10/27/2017 10:04 AM, Paul Mackerras wrote:
On Fri, Oct 27, 2017 at 09:38:17AM +0530, Aneesh Kumar K.V wrote:Hi, With hash translation mode we always tracked the hash pte slot details in linux page table. This occupied space in the linux page table and also limitted our ability to support linux features that require additional PTE bits. This series attempt to lift this limitation by not tracking slot number in linux page table. We still track slot details w.r.t Transparent Hugepage entries because an invalidate there requires us to go through all the 256 hash pte slots. So tracking whether hash page table entry is valid helps us in avoiding a lot of hcalls there. With THP entries we don't keep slot details in the primary linux page table entry but in the second half of page table. Hence tracking slot details for THP doesn't take up space in PTE. Even though we don't track slot, for removing/updating hash page table entry, PAPR hcalls expect hash page table slot details. On pseries we find slot using H_READ hcall using H_READ_4 flags. This implies an additional 2 hcalls in the updatepp and remove paths. The patch series also attempt to limit the impact of this by adding new hcalls that does remove/update of hash page table entry using hash value instead of hash page table slot. Below is the performance numbers observed when running a workload that does the below sequence for(5000) { mmap(128M) touch every page of 2048 page munmap() } The test is run with address randomization off, swap disabled in both host and guest. |------------+----------+---------------+--------------------------+-----------------------| | iterations | platform | without patch | With series and no hcall | With series and hcall | |------------+----------+---------------+--------------------------+-----------------------| | 1 | powernv | | 50.818343 | | | 2 | powernv | | 50.744123 | | | 3 | powernv | | 50.721603 | | | 4 | powernv | | 50.739922 | | | 5 | powernv | | 50.638555 | | | 1 | powernv | 51.388249 | | | | 2 | powernv | 51.789701 | | | | 3 | powernv | 52.240394 | | | | 4 | powernv | 51.432255 | | | | 5 | powernv | 51.392947 | | | |------------+----------+---------------+--------------------------+-----------------------| | 1 | pseries | | | 123.154394 | | 2 | pseries | | | 122.253956 | | 3 | pseries | | | 117.666344 | | 4 | pseries | | | 117.681479 | | 5 | pseries | | | 117.735808 | | 1 | pseries | | 119.424940 | | | 2 | pseries | | 117.663078 | | | 3 | pseries | | 118.345584 | | | 4 | pseries | | 119.620934 | | | 5 | pseries | | 119.463185 | | | 1 | pseries | 122.810867 | | | | 2 | pseries | 115.760801 | | | | 3 | pseries | 115.257030 | | | | 4 | pseries | 116.617884 | | | | 5 | pseries | 117.247036 | | | |------------+----------+---------------+--------------------------+-----------------------|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.
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 -aneesh
