From eb2dcde9f970ed8d3669444d47c8524b4bdf7d32 Mon Sep 17 00:00:00 2001 From: Vincent Donnefort Date: Fri, 28 Jun 2024 11:46:11 +0100 Subject: ring-buffer: Align meta-page to sub-buffers for improved TLB usage Previously, the mapped ring-buffer layout caused misalignment between the meta-page and sub-buffers when the sub-buffer size was not a multiple of PAGE_SIZE. This prevented hardware with larger TLB entries from utilizing them effectively. Add a padding with the zero-page between the meta-page and sub-buffers. Also update the ring-buffer map_test to verify that padding. Link: https://lore.kernel.org/20240628104611.1443542-1-vdonnefort@google.com Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) --- tools/testing/selftests/ring-buffer/map_test.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'tools/testing') diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c index a9006fa7097e..4bb0192e43f3 100644 --- a/tools/testing/selftests/ring-buffer/map_test.c +++ b/tools/testing/selftests/ring-buffer/map_test.c @@ -228,6 +228,20 @@ TEST_F(map, data_mmap) data = mmap(NULL, data_len, PROT_READ, MAP_SHARED, desc->cpu_fd, meta_len); ASSERT_EQ(data, MAP_FAILED); + + /* Verify meta-page padding */ + if (desc->meta->meta_page_size > getpagesize()) { + void *addr; + + data_len = desc->meta->meta_page_size; + data = mmap(NULL, data_len, + PROT_READ, MAP_SHARED, desc->cpu_fd, 0); + ASSERT_NE(data, MAP_FAILED); + + addr = (void *)((unsigned long)data + getpagesize()); + ASSERT_EQ(*((int *)addr), 0); + munmap(data, data_len); + } } FIXTURE(snapshot) { -- cgit v1.2.3