From nobody Thu Feb 12 21:44:14 2026 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 2F27438DC7 for ; Thu, 6 Jun 2024 17:39:22 +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=1717695563; cv=none; b=spg+gdhQjVllrhj8D2hMtRMZakjmBUGOJ1wskTOBWJJ2O5UmHql4QQtY2rwCeYIe0ZBo1V3KOxzBIlXDcrqR1uRBPFVc1N/LjoqnWrcHVqyJxzfR2fDXvmz/QTafPPtelGs3IQdUiEnCNYHjR4DWRM2EUZ1Iu8ls96uiVroi2Rs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717695563; c=relaxed/simple; bh=vzUJmp9RSaHFxKhynNzblRWh4Wso+VaChGcCRUFdtOg=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type; b=tsWSALvckSMK1kqs0efVK1dp4PSc9oCUkvDnug9OLq5dU9sdVZD1ltnwV3tbp5BcxAYxNSbyPX9yd6vYM+y2CQaTU27iPW0Csb7uw/vCj+egsiQwnYUJo+XnTriv9pHD5AwjYXyqIEtO12i6mi5QfdnCREIKZ50oam9z45TN5nw= 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 00119C32782; Thu, 6 Jun 2024 17:39:21 +0000 (UTC) Date: Thu, 6 Jun 2024 13:39:33 -0400 From: Steven Rostedt To: LKML Cc: Masami Hiramatsu , Mathieu Desnoyers , Vincent Donnefort Subject: [for-next][PATCH] ring-buffer: Align meta-page to sub-buffers for improved TLB usage Message-ID: <20240606133933.175a6b2a@rorschach.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git ring-buffer/for-next Head SHA1: ff74f987504fe90e88fdba8d80197202868ce342 Vincent Donnefort (1): ring-buffer: Align meta-page to sub-buffers for improved TLB usage ---- kernel/trace/ring_buffer.c | 29 ++++++++++++++--------= ---- tools/testing/selftests/ring-buffer/map_test.c | 14 +++++++++++++ 2 files changed, 30 insertions(+), 13 deletions(-) --------------------------- commit ff74f987504fe90e88fdba8d80197202868ce342 Author: Vincent Donnefort Date: Thu May 23 10:14:45 2024 +0100 ring-buffer: Align meta-page to sub-buffers for improved TLB usage =20 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. =20 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. =20 Link: https://lore.kernel.org/linux-trace-kernel/20240523091445.2568208= -1-vdonnefort@google.com =20 Signed-off-by: Vincent Donnefort Signed-off-by: Steven Rostedt (Google) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 28853966aa9a..41f58415c709 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -6147,10 +6147,10 @@ static void rb_setup_ids_meta_page(struct ring_buff= er_per_cpu *cpu_buffer, /* install subbuf ID to kern VA translation */ cpu_buffer->subbuf_ids =3D subbuf_ids; =20 - meta->meta_page_size =3D PAGE_SIZE; meta->meta_struct_len =3D sizeof(*meta); meta->nr_subbufs =3D nr_subbufs; meta->subbuf_size =3D cpu_buffer->buffer->subbuf_size + BUF_PAGE_HDR_SIZE; + meta->meta_page_size =3D meta->subbuf_size; =20 rb_update_meta_page(cpu_buffer); } @@ -6237,6 +6237,12 @@ static int __rb_map_vma(struct ring_buffer_per_cpu *= cpu_buffer, !(vma->vm_flags & VM_MAYSHARE)) return -EPERM; =20 + subbuf_order =3D cpu_buffer->buffer->subbuf_order; + subbuf_pages =3D 1 << subbuf_order; + + if (subbuf_order && pgoff % subbuf_pages) + return -EINVAL; + /* * Make sure the mapping cannot become writable later. Also tell the VM * to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND). @@ -6246,11 +6252,8 @@ static int __rb_map_vma(struct ring_buffer_per_cpu *= cpu_buffer, =20 lockdep_assert_held(&cpu_buffer->mapping_lock); =20 - subbuf_order =3D cpu_buffer->buffer->subbuf_order; - subbuf_pages =3D 1 << subbuf_order; - nr_subbufs =3D cpu_buffer->nr_pages + 1; /* + reader-subbuf */ - nr_pages =3D ((nr_subbufs) << subbuf_order) - pgoff + 1; /* + meta-page */ + nr_pages =3D ((nr_subbufs + 1) << subbuf_order) - pgoff; /* + meta-page */ =20 vma_pages =3D (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; if (!vma_pages || vma_pages > nr_pages) @@ -6263,20 +6266,20 @@ static int __rb_map_vma(struct ring_buffer_per_cpu = *cpu_buffer, return -ENOMEM; =20 if (!pgoff) { + unsigned long meta_page_padding; + pages[p++] =3D virt_to_page(cpu_buffer->meta_page); =20 /* - * TODO: Align sub-buffers on their size, once - * vm_insert_pages() supports the zero-page. + * Pad with the zero-page to align the meta-page with the + * sub-buffers. */ + meta_page_padding =3D subbuf_pages - 1; + while (meta_page_padding-- && p < nr_pages) + pages[p++] =3D ZERO_PAGE(vma->vm_start + (PAGE_SIZE * p)); } else { /* Skip the meta-page */ - pgoff--; - - if (pgoff % subbuf_pages) { - err =3D -EINVAL; - goto out; - } + pgoff -=3D subbuf_pages; =20 s +=3D pgoff / subbuf_pages; } 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 =3D 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 =3D desc->meta->meta_page_size; + data =3D mmap(NULL, data_len, + PROT_READ, MAP_SHARED, desc->cpu_fd, 0); + ASSERT_NE(data, MAP_FAILED); + + addr =3D (void *)((unsigned long)data + getpagesize()); + ASSERT_EQ(*((int *)addr), 0); + munmap(data, data_len); + } } =20 FIXTURE(snapshot) {