From nobody Thu Dec 18 19:07:23 2025 Received: from mail-wm1-f74.google.com (mail-wm1-f74.google.com [209.85.128.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8AC6F14A636 for ; Fri, 28 Jun 2024 10:47:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719571624; cv=none; b=WcIPWOqgRYVkefAkKG85Gqmd2T/rQXsJ4yIDEeQ0qmC4CBcjzB7UF3bKpF9N7ojMUlooUZyqTLA1EzTSJGptGSBI8oyQMlkBOZKs329x3PgdrMEs4y2z+3hlSut898nV5Ostx6LrfYCvfuzPvKdBSSdkmpwrHuCVBlMHacbd81I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719571624; c=relaxed/simple; bh=woktVHjxsn0gr5hr8+bromFgaR2dogPu6y9jS/+fBQ4=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=ZVKE173fuyereBGAYRfxqaBrUz1m+4sl7QvXNX0wxZsGASCs5kLWttNxPHpisobfM0OGHClwuWIObx7IhytF8sxbv/EhjcvzZxegQDhqpx39/HDV3Bktogtq/piWeVhdBR2u3iI/pjUuqBxnTxVZHbGIurINTgaUbS+c7LDslvs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=v4lp96/z; arc=none smtp.client-ip=209.85.128.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="v4lp96/z" Received: by mail-wm1-f74.google.com with SMTP id 5b1f17b1804b1-4256b7702a5so3132145e9.1 for ; Fri, 28 Jun 2024 03:47:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1719571621; x=1720176421; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=mVAGmQDGpiRemF1EjQXmA7rPtOTMJWbLR7/b4BT5RFw=; b=v4lp96/zQJlpT76ERcsL2tTbP+JW1NhGvQ5uwwFgTNoLRUs+SGYLfnTqQCe6DBPQ5H Mx8sryHVafGwO3Ml+GgqFaEsvXeHDDBKvafg2uceSg9jAdh3YfcRS1xgEMchyNWyGMDH 3O0L1BkzchL6I/SeZ96rgyLoCInWvppjWl11JP6RVHkvx0RyPV+d2LJEZuSJ0bxqnsst k1xNT20wPS56kysw44D516gpywYHTOBf18Uf8kidQ6A2NnQPqUxqWgf1IooY0jrM8gl6 itD8Ag1zxudVy1srXdYWT90f+b4jZk1Q3g93QQWrnBrBeDZ7uNX7b+7mOIq4iSYwLWhr d7UA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719571621; x=1720176421; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=mVAGmQDGpiRemF1EjQXmA7rPtOTMJWbLR7/b4BT5RFw=; b=sjKvj5ptOVBEeC7N454tZGO+vdOMHxsBCgmgYoVghYrSc7XBhucxdFfZPr+Y2NFBJK pOotTk12qpGAZos7UtyStjRchWRqKOcwHdVyX5BTi8sZktryNtx3G+PT/4HRvRjvvfkl 7ZxQkitI/X5JMMwbFY/Na+ulQtgHVGu24Xo5VVBVU3SQ1A91a9r70qhhv5YYFa4Ax39O SwF4WQNbuJXyoD1/t0n4TeL6MzdZgt1KRX44npUXdeMDHtyWvIDutrLypbRs8vkEnsve hD57wgb1sXKsKwXF2wcU5kgCpfZG73HtP+QTSD9gTnQ0EMZCdr/1YrqnPIGokdHsBjQi e0VQ== X-Forwarded-Encrypted: i=1; AJvYcCVqW+9RAjOGB7G2TU/8Wu5UkrDjg1TxvBIarjL6KwY053mihzqNqlx6wHBHFhf5tTl5ik2uq2xQ3LjUXsjr7o6qBErXlS2khBspj8Qb X-Gm-Message-State: AOJu0YzaK2Ma2h8MKzB+6UTYW647IenFGnfkNhdH0n7OGgm1XZ2oVZCS 33RzpzDtvlInII2EHZcWbNda/Gw8yAyIciuR8iJBZpj2dZXPIJyIWKkvexOweWEuqsEZLzE5MDk lt8UY9J4e4yowY8KxbQ== X-Google-Smtp-Source: AGHT+IHZHlvGw4nxcFoHXUEV2Mmu2bpQJUntZHoAE0zOBHagzfvEXRkaEhyc77Lxq96Bn5RGJbrsHF420JmpKzNT X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:600c:4c11:b0:425:5eee:2b75 with SMTP id 5b1f17b1804b1-4256d5a7ceamr221355e9.4.1719571620888; Fri, 28 Jun 2024 03:47:00 -0700 (PDT) Date: Fri, 28 Jun 2024 11:46:11 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.45.2.803.g4e1b14247a-goog Message-ID: <20240628104611.1443542-1-vdonnefort@google.com> Subject: [PATCH v2] ring-buffer: Align meta-page to sub-buffers for improved TLB usage From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, david@redhat.com, Vincent Donnefort Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. Signed-off-by: Vincent Donnefort -- This is based on the mm-unstable branch [1] as it depends on David's work [= 2] for allowing the zero-page in vm_insert_page(). [1] https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git [2] https://lore.kernel.org/all/20240522125713.775114-1-david@redhat.com v1 -> v2: * Fix unsequenced modification and access to 'p' (s390 build) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 7345a8b625fb..c1116e76fe17 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -6148,10 +6148,10 @@ 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); } @@ -6238,6 +6238,12 @@ 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). @@ -6247,11 +6253,8 @@ 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) @@ -6264,20 +6267,24 @@ 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. */ - } else { - /* Skip the meta-page */ - pgoff--; + meta_page_padding =3D subbuf_pages - 1; + while (meta_page_padding-- && p < nr_pages) { + unsigned long __maybe_unused zero_addr =3D + vma->vm_start + (PAGE_SIZE * p); =20 - if (pgoff % subbuf_pages) { - err =3D -EINVAL; - goto out; + pages[p++] =3D ZERO_PAGE(zero_addr); } + } else { + /* Skip the meta-page */ + 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) { base-commit: c65920c76a977c2b73c3a8b03b4c0c00cc1285ed --=20 2.45.2.803.g4e1b14247a-goog