linux-kernel - [PATCH RFC v2 03/27] mm: cma: Make CMA_ALLOC

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Date:   Sun, 19 Nov 2023 16:56:57 +0000
From:   Alexandru Elisei <alexandru.elisei@....com>
To:     catalin.marinas@....com, will@...nel.org, oliver.upton@...ux.dev,
        maz@...nel.org, james.morse@....com, suzuki.poulose@....com,
        yuzenghui@...wei.com, arnd@...db.de, akpm@...ux-foundation.org,
        mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
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        bristot@...hat.com, vschneid@...hat.com, mhiramat@...nel.org,
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Cc:     pcc@...gle.com, steven.price@....com, anshuman.khandual@....com,
        vincenzo.frascino@....com, david@...hat.com, eugenis@...gle.com,
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        linux-trace-kernel@...r.kernel.org
Subject: [PATCH RFC v2 03/27] mm: cma: Make CMA_ALLOC_SUCCESS/FAIL count the number of pages

The CMA_ALLOC_SUCCESS, respectively CMA_ALLOC_FAIL, are increased by one
after each cma_alloc() function call. This is done even though cma_alloc()
can allocate an arbitrary number of CMA pages. When looking at
/proc/vmstat, the number of successful (or failed) cma_alloc() calls
doesn't tell much with regards to how many CMA pages were allocated via
cma_alloc() versus via the page allocator (regular allocation request or
PCP lists refill).

This can also be rather confusing to a user who isn't familiar with the
code, since the unit of measurement for nr_free_cma is the number of pages,
but cma_alloc_success and cma_alloc_fail count the number of cma_alloc()
function calls.

Let's make this consistent, and arguably more useful, by having
CMA_ALLOC_SUCCESS count the number of successfully allocated CMA pages, and
CMA_ALLOC_FAIL count the number of pages cma_alloc() failed to allocate.

For users that wish to track the number of cma_alloc() calls, there are
tracepoints for that already implemented.

Signed-off-by: Alexandru Elisei <alexandru.elisei@....com>
---
 mm/cma.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 2b2494fd6b59..2b74db5116d5 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -517,10 +517,10 @@ struct page *cma_alloc(struct cma *cma, unsigned long count,
 	pr_debug("%s(): returned %p\n", __func__, page);
 out:
 	if (page) {
-		count_vm_event(CMA_ALLOC_SUCCESS);
+		count_vm_events(CMA_ALLOC_SUCCESS, count);
 		cma_sysfs_account_success_pages(cma, count);
 	} else {
-		count_vm_event(CMA_ALLOC_FAIL);
+		count_vm_events(CMA_ALLOC_FAIL, count);
 		if (cma)
 			cma_sysfs_account_fail_pages(cma, count);
 	}
-- 
2.42.1