From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6383414D2B4; Wed, 21 Aug 2024 15:56:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724255770; cv=none; b=VsWu7VF158HGwSe9Yib1SmrGd7IaLFHG8lfxbiWYuPtZQzQJKyw10oBX74d0AUf8wKzb2elJcTym0XT6zSToPFKZfiYzjSMahrLStq/HXGXyQIJZLWPa+rEtPFAIXfy7i/1DNtucDwWMAgsjCLgPUHPZIDIhl9iyv6THheWajJ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724255770; c=relaxed/simple; bh=tk3tV88gD6hBTFFbuvzrZ2GOP6Y+PNIPKOVHzLmKSko=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=TKxHONyowtnigK1CJp7s1y7jqi0o6SjQJ7LLR6zVjCQpEvKaT3eSa8iq5T22HB6W5Yc5W1I/+AjLSBOOL7L9HZXbpCEV10892FKTN1xBzPR9aLNsc43liSEBTAfSRbdlFoA/FP5etjVwOb0unh3mOR1BdnlktWalXJagry4qoK8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0AA5C32781; Wed, 21 Aug 2024 15:56:07 +0000 (UTC) Date: Wed, 21 Aug 2024 11:56:36 -0400 From: Steven Rostedt To: Vincent Donnefort Cc: mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com, kernel-team@android.com, david@redhat.com Subject: Re: [PATCH v2] ring-buffer: Align meta-page to sub-buffers for improved TLB usage Message-ID: <20240821115636.3546f684@gandalf.local.home> In-Reply-To: <20240628104611.1443542-1-vdonnefort@google.com> References: <20240628104611.1443542-1-vdonnefort@google.com> X-Mailer: Claws Mail 3.20.0git84 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 28 Jun 2024 11:46:11 +0100 Vincent Donnefort wrote: > 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); Should we make this a test that the entire page is zero? for (int i = desc->meta->meta_struct_len; i < desc->meta->meta_page_size; i += sizeof(int)) ASSERT_EQ(((int *)data)[i], 0); ? > + munmap(data, data_len); > + } > } Also, looking at the init, if for some reason (I highly doubt it may happen) that the meta_struct_len becomes bigger than page_size, we should update the init section to: /* Handle the case where meta_struct_len is greater than page size */ if (page_size < desc->meta->meta_struct_len) { /* meta_page_size is >= meta_struct_len */ page_size = desc->meta->meta_page_size; munmap(desc->meta, page_size); map = mmap(NULL, page_size, PROT_READ, MAP_SHARED, desc->cpu_fd, 0); if (map == MAP_FAILED) return -errno; desc->meta = (struct trace_buffer_meta *)map; } -- Steve