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?
Can you give us the mean and standard deviation for each set of 5
please?
Paul.
