linux-kernel - [PATCH 1/1] mm: handle profiling for fake memory allocations during compaction

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Message-ID: <20240614230504.3849136-1-surenb@google.com>
Date: Fri, 14 Jun 2024 16:05:04 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: akpm@...ux-foundation.org
Cc: kent.overstreet@...ux.dev, vbabka@...e.cz, pasha.tatashin@...een.com, 
	souravpanda@...gle.com, keescook@...omium.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, Suren Baghdasaryan <surenb@...gle.com>
Subject: [PATCH 1/1] mm: handle profiling for fake memory allocations during compaction

During compaction isolated free pages are marked allocated so that they
can be split and/or freed. For that, post_alloc_hook() is used inside
split_map_pages() and release_free_list(). split_map_pages() marks free
pages allocated, splits the pages and then lets alloc_contig_range_noprof()
free those pages. release_free_list() marks free pages and immediately
frees them. This usage of post_alloc_hook() affect memory allocation
profiling because these functions might not be called from an instrumented
allocator, therefore current->alloc_tag is NULL and when debugging is
enabled (CONFIG_MEM_ALLOC_PROFILING_DEBUG=y) that causes warnings.
To avoid that, wrap such post_alloc_hook() calls into an instrumented
function which acts as an allocator which will be charged for these
fake allocations. Note that these allocations are very short lived until
they are freed, therefore the associated counters should usually read 0.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
---
 mm/compaction.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index e731d45befc7..739b1bf3d637 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -79,6 +79,13 @@ static inline bool is_via_compact_memory(int order) { return false; }
 #define COMPACTION_HPAGE_ORDER	(PMD_SHIFT - PAGE_SHIFT)
 #endif

+static struct page *mark_allocated_noprof(struct page *page, unsigned int order, gfp_t gfp_flags)
+{
+	post_alloc_hook(page, order, __GFP_MOVABLE);
+	return page;
+}
+#define mark_allocated(...)	alloc_hooks(mark_allocated_noprof(__VA_ARGS__))
+
 static void split_map_pages(struct list_head *freepages)
 {
 	unsigned int i, order;
@@ -93,7 +100,7 @@ static void split_map_pages(struct list_head *freepages)

 			nr_pages = 1 << order;

-			post_alloc_hook(page, order, __GFP_MOVABLE);
+			mark_allocated(page, order, __GFP_MOVABLE);
 			if (order)
 				split_page(page, order);

@@ -122,7 +129,7 @@ static unsigned long release_free_list(struct list_head *freepages)
 			 * Convert free pages into post allocation pages, so
 			 * that we can free them via __free_page.
 			 */
-			post_alloc_hook(page, order, __GFP_MOVABLE);
+			mark_allocated(page, order, __GFP_MOVABLE);
 			__free_pages(page, order);
 			if (pfn > high_pfn)
 				high_pfn = pfn;

base-commit: c286c21ff94252f778515b21b6bebe749454a852
-- 
2.45.2.627.g7a2c4fd464-goog