From patchwork Fri Feb 2 21:53:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 13543485 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CBA39C4828E for ; Fri, 2 Feb 2024 21:56:09 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rW1UK-0008TQ-Hk; Fri, 02 Feb 2024 16:54:20 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rW1UI-0008Lg-Fx for qemu-devel@nongnu.org; Fri, 02 Feb 2024 16:54:18 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rW1UA-0004uV-Ni for qemu-devel@nongnu.org; Fri, 02 Feb 2024 16:54:18 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1706910850; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=77r2j9eRnlux52n9mVjVt4CTYLtK8feRXEl2IUvTNLM=; b=EY4t4n9hBsfXpm+EWex8duGH9BGe5SHgBBhruSJJyBFqmisEPRUEjBi/jvR2LSaJaKWbV8 lNInLYlQ+doMjFhNyrARJOjhV29NKB9VMAjjnnspTIQn8Yalhw6itrNXYI5AvBq7bN57cA 3uZ5plyr7eqjqDWDVRXi8PmpCeTiwy8= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-558-VEH01V6kP-u9EfeQSdCp_w-1; Fri, 02 Feb 2024 16:54:08 -0500 X-MC-Unique: VEH01V6kP-u9EfeQSdCp_w-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 056D029AA38E; Fri, 2 Feb 2024 21:54:08 +0000 (UTC) Received: from t14s.redhat.com (unknown [10.39.192.47]) by smtp.corp.redhat.com (Postfix) with ESMTP id 791022166B31; Fri, 2 Feb 2024 21:54:06 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Cc: David Hildenbrand , "Michael S . Tsirkin" , Jason Wang , Stefan Hajnoczi , Stefano Garzarella , Germano Veit Michel , Raphael Norwitz Subject: [PATCH v1 12/15] libvhost-user: Use most of mmap_offset as fd_offset Date: Fri, 2 Feb 2024 22:53:29 +0100 Message-ID: <20240202215332.118728-13-david@redhat.com> In-Reply-To: <20240202215332.118728-1-david@redhat.com> References: <20240202215332.118728-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.133.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.276, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, T_SCC_BODY_TEXT_LINE=-0.01, T_SPF_TEMPERROR=0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org In the past, QEMU would create memory regions that could partially cover hugetlb pages, making mmap() fail if we would use the mmap_offset as an fd_offset. For that reason, we never used the mmap_offset as an offset into the fd and instead always mapped the fd from the very start. However, that can easily result in us mmap'ing a lot of unnecessary parts of an fd, possibly repeatedly. QEMU nowadays does not create memory regions that partially cover huge pages -- it never really worked with postcopy. QEMU handles merging of regions that partially cover huge pages (due to holes in boot memory) since 2018 in c1ece84e7c93 ("vhost: Huge page align and merge"). Let's be a bit careful and not unconditionally convert the mmap_offset into an fd_offset. Instead, let's simply detect the hugetlb size and pass as much as we can as fd_offset, making sure that we call mmap() with a properly aligned offset. With QEMU and a virtio-mem device that is fully plugged (50GiB using 50 memslots) the qemu-storage daemon process consumes in the VA space 1281GiB before this change and 58GiB after this change. Example debug output: ================ Vhost user message ================ Request: VHOST_USER_ADD_MEM_REG (37) Flags: 0x9 Size: 40 Fds: 59 Adding region 50 guest_phys_addr: 0x0000000d80000000 memory_size: 0x0000000040000000 userspace_addr 0x00007f54ebffe000 mmap_offset 0x0000000c00000000 fd_offset: 0x0000000c00000000 new mmap_offset: 0x0000000000000000 mmap_addr: 0x00007f7ecc000000 Successfully added new region ================ Vhost user message ================ Request: VHOST_USER_ADD_MEM_REG (37) Flags: 0x9 Size: 40 Fds: 59 Adding region 51 guest_phys_addr: 0x0000000dc0000000 memory_size: 0x0000000040000000 userspace_addr 0x00007f552bffe000 mmap_offset 0x0000000c40000000 fd_offset: 0x0000000c40000000 new mmap_offset: 0x0000000000000000 mmap_addr: 0x00007f7e8c000000 Successfully added new region Signed-off-by: David Hildenbrand Reviewed-by: Raphael Norwitz --- subprojects/libvhost-user/libvhost-user.c | 50 ++++++++++++++++++++--- 1 file changed, 45 insertions(+), 5 deletions(-) diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c index 75e47b7bb3..7d8293dc84 100644 --- a/subprojects/libvhost-user/libvhost-user.c +++ b/subprojects/libvhost-user/libvhost-user.c @@ -43,6 +43,8 @@ #include #include #include +#include +#include #ifdef __NR_userfaultfd #include @@ -281,12 +283,36 @@ vu_remove_all_mem_regs(VuDev *dev) dev->nregions = 0; } +static size_t +get_fd_pagesize(int fd) +{ + static size_t pagesize; +#if defined(__linux__) + struct statfs fs; + int ret; + + do { + ret = fstatfs(fd, &fs); + } while (ret != 0 && errno == EINTR); + + if (!ret && fs.f_type == HUGETLBFS_MAGIC) { + return fs.f_bsize; + } +#endif + + if (!pagesize) { + pagesize = getpagesize(); + } + return pagesize; +} + static void _vu_add_mem_reg(VuDev *dev, VhostUserMemoryRegion *msg_region, int fd) { const uint64_t start_gpa = msg_region->guest_phys_addr; const uint64_t end_gpa = start_gpa + msg_region->memory_size; int prot = PROT_READ | PROT_WRITE; + uint64_t mmap_offset, fd_offset; VuDevRegion *r; void *mmap_addr; int low = 0; @@ -335,11 +361,25 @@ _vu_add_mem_reg(VuDev *dev, VhostUserMemoryRegion *msg_region, int fd) idx = low; /* - * We don't use offset argument of mmap() since the mapped address has - * to be page aligned, and we use huge pages. + * Convert most of msg_region->mmap_offset to fd_offset. In almost all + * cases, this will leave us with mmap_offset == 0, mmap()'ing only + * what we really need. Only if a memory region would partially cover + * hugetlb pages, we'd get mmap_offset != 0, which usually doesn't happen + * anymore (i.e., modern QEMU). + * + * Note that mmap() with hugetlb would fail if the offset into the file + * is not aligned to the huge page size. */ - mmap_addr = mmap(0, msg_region->memory_size + msg_region->mmap_offset, - prot, MAP_SHARED | MAP_NORESERVE, fd, 0); + fd_offset = ALIGN_DOWN(msg_region->mmap_offset, get_fd_pagesize(fd)); + mmap_offset = msg_region->mmap_offset - fd_offset; + + DPRINT(" fd_offset: 0x%016"PRIx64"\n", + fd_offset); + DPRINT(" adj mmap_offset: 0x%016"PRIx64"\n", + mmap_offset); + + mmap_addr = mmap(0, msg_region->memory_size + mmap_offset, + prot, MAP_SHARED | MAP_NORESERVE, fd, fd_offset); if (mmap_addr == MAP_FAILED) { vu_panic(dev, "region mmap error: %s", strerror(errno)); return; @@ -354,7 +394,7 @@ _vu_add_mem_reg(VuDev *dev, VhostUserMemoryRegion *msg_region, int fd) r->size = msg_region->memory_size; r->qva = msg_region->userspace_addr; r->mmap_addr = (uint64_t)(uintptr_t)mmap_addr; - r->mmap_offset = msg_region->mmap_offset; + r->mmap_offset = mmap_offset; dev->nregions++; if (dev->postcopy_listening) {