linux-kernel - [PATCH v5 05/14] perf bench mem: Switch from zalloc() to mmap()

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Message-Id: <20250710005926.1159009-6-ankur.a.arora@oracle.com>
Date: Wed,  9 Jul 2025 17:59:17 -0700
From: Ankur Arora <ankur.a.arora@...cle.com>
To: linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Cc: akpm@...ux-foundation.org, david@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
        mjguzik@...il.com, luto@...nel.org, peterz@...radead.org,
        acme@...nel.org, namhyung@...nel.org, tglx@...utronix.de,
        willy@...radead.org, raghavendra.kt@....com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
        ankur.a.arora@...cle.com
Subject: [PATCH v5 05/14] perf bench mem: Switch from zalloc() to mmap()

Using mmap() ensures that the buffer is always aligned at a fixed
boundary. Switch to that to remove one source of variability.

Since we always want to read/write from the the allocated buffers map
with pagetables pre-populated.

Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 tools/perf/bench/mem-functions.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/tools/perf/bench/mem-functions.c b/tools/perf/bench/mem-functions.c
index 06d3ee6f5d69..914f9048d982 100644
--- a/tools/perf/bench/mem-functions.c
+++ b/tools/perf/bench/mem-functions.c
@@ -22,9 +22,9 @@
 #include <string.h>
 #include <unistd.h>
 #include <sys/time.h>
+#include <sys/mman.h>
 #include <errno.h>
 #include <linux/time64.h>
-#include <linux/zalloc.h>
 
 #define K 1024
 
@@ -285,16 +285,33 @@ static int do_memcpy(const struct function *r, struct bench_params *p,
 	return 0;
 }
 
+static void *bench_mmap(size_t size, bool populate)
+{
+	void *p;
+	int extra = populate ? MAP_POPULATE : 0;
+
+	p = mmap(NULL, size, PROT_READ|PROT_WRITE,
+		 extra | MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
+
+	return p == MAP_FAILED ? NULL : p;
+}
+
+static void bench_munmap(void *p, size_t size)
+{
+	if (p)
+		munmap(p, size);
+}
+
 static bool mem_alloc(struct bench_mem_info *info, struct bench_params *p,
 		      void **src, void **dst)
 {
 	bool failed;
 
-	*dst = zalloc(p->size);
+	*dst = bench_mmap(p->size, true);
 	failed = *dst == NULL;
 
 	if (info->alloc_src) {
-		*src = zalloc(p->size);
+		*src = bench_mmap(p->size, true);
 		failed = failed || *src == NULL;
 	}
 
@@ -305,8 +322,8 @@ static void mem_free(struct bench_mem_info *info __maybe_unused,
 		     struct bench_params *p __maybe_unused,
 		     void **src, void **dst)
 {
-	free(*dst);
-	free(*src);
+	bench_munmap(*dst, p->size);
+	bench_munmap(*src, p->size);
 
 	*dst = *src = NULL;
 }
-- 
2.43.5