On 4/9/25 19:30, Brendan Jackman wrote:
From 8ff20dbb52770d082e182482d2b47e521de028d1 Mon Sep 17 00:00:00 2001 From: Brendan Jackman jackmanb@google.com Date: Wed, 9 Apr 2025 17:22:14 +000 Subject: [PATCH] page_alloc: speed up fallbacks in rmqueue_bulk() - comment updates
Tidy up some terminology and redistribute commentary. Signed-off-by: Brendan Jackman jackmanb@google.com
LGTM (assuming folding)
mm/page_alloc.c | 22 +++++++++------------- 1 file changed, 9 insertions(+), 13 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index dfb2b3f508af4..220bd0bcc38c3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2183,21 +2183,13 @@ try_to_claim_block(struct zone *zone, struct page *page, } /*
- Try finding a free buddy page on the fallback list.
- This will attempt to claim a whole pageblock for the requested type
- to ensure grouping of such requests in the future.
- If a whole block cannot be claimed, steal an individual page, regressing to
- __rmqueue_smallest() logic to at least break up as little contiguity as
- possible.
- Try to allocate from some fallback migratetype by claiming the entire block,
*/
- i.e. converting it to the allocation's start migratetype.
- The use of signed ints for order and current_order is a deliberate
- deviation from the rest of this file, to make the for loop
- condition simpler.
-/* Try to claim a whole foreign block, take a page, expand the remainder */ static __always_inline struct page * __rmqueue_claim(struct zone *zone, int order, int start_migratetype, unsigned int alloc_flags) @@ -2247,7 +2239,10 @@ __rmqueue_claim(struct zone *zone, int order, int start_migratetype, return NULL; } -/* Try to steal a single page from a foreign block */ +/*
- Try to steal a single page from some fallback migratetype. Leave the rest of
- the block as its current migratetype, potentially causing fragmentation.
- */
static __always_inline struct page * __rmqueue_steal(struct zone *zone, int order, int start_migratetype) { @@ -2307,7 +2302,8 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, } /*
* Try the different freelists, native then foreign.
* First try the freelists of the requested migratetype, then try* fallbacks modes with increasing levels of fragmentation risk. * * The fallback logic is expensive and rmqueue_bulk() calls in * a loop with the zone->lock held, meaning the freelists are@@ -2332,7 +2328,7 @@ __rmqueue(struct zone *zone, unsigned int order, int migratetype, case RMQUEUE_CLAIM: page = __rmqueue_claim(zone, order, migratetype, alloc_flags); if (page) {
/* Replenished native freelist, back to normal mode */
/* Replenished preferred freelist, back to normal mode. */ *mode = RMQUEUE_NORMAL; return page; }base-commit: aa42382db4e2a4ed1f4ba97ffc50e2ce45accb0c