netdev - [PATCH net-next 3/3] selftests: net: tcp_mmap: Use huge pages in receive path

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Date:   Thu, 20 Aug 2020 10:11:18 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>,
        Arjun Roy <arjunroy@...gle.com>
Subject: [PATCH net-next 3/3] selftests: net: tcp_mmap: Use huge pages in
 receive path

One down side of using TCP rx zerocopy is one extra TLB miss
per page after the mapping operation.

While if the application is using hugepages, the non zerocopy
recvmsg() will not have to pay these TLB costs.

This patch allows server side to use huge pages for
the non zero copy case, to allow fair comparisons when
both solutions use optimal conditions.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Arjun Roy <arjunroy@...gle.com>
Cc: Soheil Hassas Yeganeh <soheil@...gle.com>
---
 tools/testing/selftests/net/tcp_mmap.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/net/tcp_mmap.c b/tools/testing/selftests/net/tcp_mmap.c
index ca2618f3e7a12ab6863665f465dea2e8d469131b..00f837c9bc6c4549c19dfc27aa2d08c454ea169e 100644
--- a/tools/testing/selftests/net/tcp_mmap.c
+++ b/tools/testing/selftests/net/tcp_mmap.c
@@ -157,6 +157,7 @@ void *child_thread(void *arg)
 	void *addr = NULL;
 	double throughput;
 	struct rusage ru;
+	size_t buffer_sz;
 	int lu, fd;
 
 	fd = (int)(unsigned long)arg;
@@ -164,9 +165,9 @@ void *child_thread(void *arg)
 	gettimeofday(&t0, NULL);
 
 	fcntl(fd, F_SETFL, O_NDELAY);
-	buffer = malloc(chunk_size);
-	if (!buffer) {
-		perror("malloc");
+	buffer = mmap_large_buffer(chunk_size, &buffer_sz);
+	if (buffer == (void *)-1) {
+		perror("mmap");
 		goto error;
 	}
 	if (zflg) {
@@ -256,7 +257,7 @@ void *child_thread(void *arg)
 				ru.ru_nvcsw);
 	}
 error:
-	free(buffer);
+	munmap(buffer, buffer_sz);
 	close(fd);
 	if (zflg)
 		munmap(raddr, chunk_size + map_align);
-- 
2.28.0.297.g1956fa8f8d-goog