diff options
| author | Brendan Jackman <jackmanb@google.com> | 2025-02-28 09:52:17 +0000 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-03-17 00:05:35 -0700 |
| commit | e47f1f56dd82cc6d91f5c4d914a534aa03cd12ca (patch) | |
| tree | 6af19783e5a6427a55db9c7c73678c4702fd2abb /mm/compaction.c | |
| parent | c36549ff8d8423fbf1a0c5bbd72be4f902d74700 (diff) | |
mm/page_alloc: clarify terminology in migratetype fallback code
Patch series "mm/page_alloc: Some clarifications for migratetype
fallback", v4.
A couple of patches to try and make the code easier to follow.
This patch (of 2):
This code is rather confusing because:
1. "Steal" is sometimes used to refer to the general concept of
allocating from a from a block of a fallback migratetype
(steal_suitable_fallback()) but sometimes it refers specifically to
converting a whole block's migratetype (can_steal_fallback()).
2. can_steal_fallback() sounds as though it's answering the question "am
I functionally permitted to allocate from that other type" but in
fact it is encoding a heuristic preference.
3. The same piece of data has different names in different places:
can_steal vs whole_block. This reinforces point 2 because it looks
like the different names reflect a shift in intent from "am I
allowed to steal" to "do I want to steal", but no such shift exists.
Fix 1. by avoiding the term "steal" in ambiguous contexts. Start using
the term "claim" to refer to the special case of stealing the entire
block.
Fix 2. by using "should" instead of "can", and also rename its
parameters and add some commentary to make it more explicit what they
mean.
Fix 3. by adopting the new "claim" terminology universally for this
set of variables.
Link: https://lkml.kernel.org/r/20250228-clarify-steal-v4-0-cb2ef1a4e610@google.com
Link: https://lkml.kernel.org/r/20250228-clarify-steal-v4-1-cb2ef1a4e610@google.com
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/compaction.c')
| -rw-r--r-- | mm/compaction.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index a3203d97123e..2e2d4db33e68 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -2332,7 +2332,7 @@ static enum compact_result __compact_finished(struct compact_control *cc) ret = COMPACT_NO_SUITABLE_PAGE; for (order = cc->order; order < NR_PAGE_ORDERS; order++) { struct free_area *area = &cc->zone->free_area[order]; - bool can_steal; + bool claim_block; /* Job done if page is free of the right migratetype */ if (!free_area_empty(area, migratetype)) @@ -2349,7 +2349,7 @@ static enum compact_result __compact_finished(struct compact_control *cc) * other migratetype buddy lists. */ if (find_suitable_fallback(area, order, migratetype, - true, &can_steal) != -1) + true, &claim_block) != -1) /* * Movable pages are OK in any pageblock. If we are * stealing for a non-movable allocation, make sure |