SuperPages utilization survey

[Robert N. M. Watson]

On 9 Jun 2012, at 10:46, Mikolaj Golub wrote:

> On Sat, 9 Jun 2012 12:07:40 +0300 Konstantin Belousov wrote:
> 
> KB> Well, if I see a report informing me that some 2M region contains 512 super
> KB> pages, how should I interpret it ? For me, it is only one superpage (mapping)
> KB> that can be created in one 2M region.
> 
> Well, if I see a report like below:
> 
>  PID              START                END PRT    RES PRES   SUP REF SHD  FL TP PATH
> 48568        0x800c00000        0x820c00000 rw- 131072    0 51712   2   0 --S df 
> 
> it tells me that for the region 0x800c00000-0x820c00000 (512Mb) we have 131072
> * 4k = 512Mb resident and 51712 * 4k = 202Mb (a litle less than a half of the
> region) promoted (mapped) to superpages.
> 
> If I had number of superpages here I would need additional knowledge (a
> superpage size) to calculate how effectively superpages are used.
> 
> But actually, no much difference for me. To get a number of superpages is it
> enough just to divide the result obtained counting normal-sized pages by
> (2M/4k) factor?


Remember also that superpage sizes are not necessarily 2M on all architectures, and in principle, many different page sizes might be simultaneously supported (e.g., on MIPS). I wonder if there's some way to capture that notion in the output somewhere so that, if we start supporting more granular page size control (something Alan might comment on), tool output doesn't need to be changed.

Robert