On Sun, 16 Oct 2011 10:01:36 +0200 "Michal Nazarewicz" wrote:
Still, as I think of it now, maybe alloc_contig_free_range() would be
better?
On Sun, 16 Oct 2011 10:31:16 +0200, Andrew Morton wrote:
Nope. Of *course* the pages were free. Otherwise we couldn't
(re)allocate them. I still think the "free" part is redundant.
Makes sense.
What could be improved is the "alloc" part. This really isn't an
allocation operation. The pages are being removed from buddy then
moved into the free arena of a different memory manager from where they
will _later_ be "allocated".
Not quite. After alloc_contig_range() returns, the pages are passed with
no further processing to the caller. Ie. the area is not later split into
several parts nor kept in CMA's pool unused.
alloc_contig_freed_pages() is a little different since it must be called on
a buddy page boundary and may return more then requested (because of the way
buddy system merges buddies) so there is a little processing after it returns
(namely freeing of the excess pages).
So we should move away from the alloc/free naming altogether for this
operation and think up new terms. How about "claim" and "release"?
claim_contig_pages, claim_contig_range, release_contig_pages, etc?
Or we could use take/return.
Personally, I'm not convinced about changing the names of alloc_contig_range()
and free_contig_pages() but I see merit in changing alloc_contig_freed_pages()
to something else.
Since at the moment, it's used only by alloc_contig_range(), I'd lean
towards removing it from page-isolation.h, marking as static and renaming
to __alloc_contig_range().
Also, if we have no expectation that anything apart from CMA will use
these interfaces (?), the names could/should be prefixed with "cma_".
In Kamezawa's original patchset, he used those for a bit different
approach (IIRC, Kamezawa's patchset introduced a function that scanned memory
and tried to allocate contiguous memory where it could), so I can imagine that
someone will make use of those functions. It may be used in any situation
where a range of pages is either free (ie. in buddy system) or movable and
one wants to allocate them for some reason.
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.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michal "mina86" Nazarewicz (o o)
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