Re: [RFC PATCH 5/6] zsmalloc: introduce handle mapping API

[Sergey Senozhatsky]

On (25/01/28 14:29), Sergey Senozhatsky wrote:
> Maybe copy-in is just an okay thing to do.  Let me try to measure.

Naaah, not really okay.  On our memory-pressure test (4GB device, 4
CPUs) that kmap_local thingy appears to save approx 6GB of memcpy().

CPY stats: 734954 1102903168 4926116 6566654656

There were 734954 cases when we memcpy() [object spans two pages] with
accumulated size of 1102903168 bytes, and 4926116 cases when we took
a shortcut via kmap_local and avoided memcpy(), with accumulated size
of 6566654656 bytes.

In both cases I counted only RO direction for map, and WO direction
for unmap.