Hi Christoph,
On Tue, 11 Nov 2014, Christoph Lameter wrote:
On Wed, 12 Nov 2014, SeongJae Park wrote:
Difference with cma is choice and operation of 2nd-class client. In gcma,
2nd-class client should allocate pages from the reserved area only if the
allocated pages mets following conditions.
How about making CMA configurable in some fashion to be able to specify
the type of 2nd class clients? Clean page-cache pages can also be rather
easily evicted (see zone-reclaim). You could migrate them out when they
are dirtied so that you do not have the high writeback latency from the
CMA reserved area if it needs to be evicted later.
Nice point.
Currently, gcma is integrated inside cma and user could decide a specific
contiguous memory area to work in cma way(movable pages as 2nd class) or
in gcma way(out-of-kernel, easy-to-discard pages as 2nd class).
It is implemented in 6th change of this RFC, "gcma: integrate gcma under
cma interface".
In short, the 2nd-clients of cma is already configurable between
movable pages and frontswap backend with this RFC.
And yes, cleancache will be great 2nd class client.
As described within coverletter, our 2nd class client candidates are
frontswap and _cleancache_. But, because the gcma is still in unmatured
sate yet, current RFC(this patchset) use only frontswap.
In future, it will be configurable.
Apologize I forgot to describe about future plan.
Thanks,
SeongJae Park
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