From patchwork Mon Aug 8 06:35:31 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Liang Li X-Patchwork-Id: 9266823 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 70EE360839 for ; Mon, 8 Aug 2016 06:44:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 5FA2A1FF65 for ; Mon, 8 Aug 2016 06:44:41 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 5281027DA4; Mon, 8 Aug 2016 06:44:41 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 530E8279B3 for ; Mon, 8 Aug 2016 06:44:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752513AbcHHGoX (ORCPT ); Mon, 8 Aug 2016 02:44:23 -0400 Received: from mga04.intel.com ([192.55.52.120]:44890 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752291AbcHHGnX (ORCPT ); Mon, 8 Aug 2016 02:43:23 -0400 Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga104.fm.intel.com with ESMTP; 07 Aug 2016 23:43:21 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,488,1464678000"; d="scan'208";a="1021448620" Received: from ll.sh.intel.com (HELO localhost) ([10.239.13.123]) by fmsmga001.fm.intel.com with ESMTP; 07 Aug 2016 23:43:18 -0700 From: Liang Li To: linux-kernel@vger.kernel.org Cc: virtualization@lists.linux-foundation.org, linux-mm@kvack.org, virtio-dev@lists.oasis-open.org, kvm@vger.kernel.org, qemu-devel@nongnu.org, quintela@redhat.com, dgilbert@redhat.com, dave.hansen@intel.com, Liang Li , "Michael S. Tsirkin" , Paolo Bonzini , Cornelia Huck , Amit Shah Subject: [PATCH v3 kernel 4/7] virtio-balloon: speed up inflate/deflate process Date: Mon, 8 Aug 2016 14:35:31 +0800 Message-Id: <1470638134-24149-5-git-send-email-liang.z.li@intel.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1470638134-24149-1-git-send-email-liang.z.li@intel.com> References: <1470638134-24149-1-git-send-email-liang.z.li@intel.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP The implementation of the current virtio-balloon is not very efficient, the time spends on different stages of inflating the balloon to 7GB of a 8GB idle guest: a. allocating pages (6.5%) b. sending PFNs to host (68.3%) c. address translation (6.1%) d. madvise (19%) It takes about 4126ms for the inflating process to complete. Debugging shows that the bottle neck are the stage b and stage d. If using a bitmap to send the page info instead of the PFNs, we can reduce the overhead in stage b quite a lot. Furthermore, we can do the address translation and call madvise() with a bulk of RAM pages, instead of the current page per page way, the overhead of stage c and stage d can also be reduced a lot. This patch is the kernel side implementation which is intended to speed up the inflating & deflating process by adding a new feature to the virtio-balloon device. With this new feature, inflating the balloon to 7GB of a 8GB idle guest only takes 590ms, the performance improvement is about 85%. TODO: optimize stage a by allocating/freeing a chunk of pages instead of a single page at a time. Signed-off-by: Liang Li Suggested-by: Michael S. Tsirkin Cc: Michael S. Tsirkin Cc: Paolo Bonzini Cc: Cornelia Huck Cc: Amit Shah Cc: Dave Hansen --- drivers/virtio/virtio_balloon.c | 233 +++++++++++++++++++++++++++++++++++----- 1 file changed, 209 insertions(+), 24 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 59ffe5a..c31839c 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -42,6 +42,10 @@ #define OOM_VBALLOON_DEFAULT_PAGES 256 #define VIRTBALLOON_OOM_NOTIFY_PRIORITY 80 +#define BALLOON_BMAP_SIZE (8 * PAGE_SIZE) +#define PFNS_PER_BMAP (BALLOON_BMAP_SIZE * BITS_PER_BYTE) +#define BALLOON_BMAP_COUNT 32 + static int oom_pages = OOM_VBALLOON_DEFAULT_PAGES; module_param(oom_pages, int, S_IRUSR | S_IWUSR); MODULE_PARM_DESC(oom_pages, "pages to free on OOM"); @@ -67,6 +71,13 @@ struct virtio_balloon { /* Number of balloon pages we've told the Host we're not using. */ unsigned int num_pages; + /* Pointer of the bitmap header. */ + void *bmap_hdr; + /* Bitmap and bitmap count used to tell the host the pages */ + unsigned long *page_bitmap[BALLOON_BMAP_COUNT]; + unsigned int nr_page_bmap; + /* Used to record the processed pfn range */ + unsigned long min_pfn, max_pfn, start_pfn, end_pfn; /* * The pages we've told the Host we're not using are enqueued * at vb_dev_info->pages list. @@ -110,16 +121,66 @@ static void balloon_ack(struct virtqueue *vq) wake_up(&vb->acked); } +static inline void init_pfn_range(struct virtio_balloon *vb) +{ + vb->min_pfn = ULONG_MAX; + vb->max_pfn = 0; +} + +static inline void update_pfn_range(struct virtio_balloon *vb, + struct page *page) +{ + unsigned long balloon_pfn = page_to_balloon_pfn(page); + + if (balloon_pfn < vb->min_pfn) + vb->min_pfn = balloon_pfn; + if (balloon_pfn > vb->max_pfn) + vb->max_pfn = balloon_pfn; +} + static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) { - struct scatterlist sg; - unsigned int len; + struct scatterlist sg, sg2[BALLOON_BMAP_COUNT + 1]; + unsigned int len, i; + + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_PAGE_BITMAP)) { + struct balloon_bmap_hdr *hdr = vb->bmap_hdr; + unsigned long bmap_len; + int nr_pfn, nr_used_bmap, nr_buf; + + nr_pfn = vb->end_pfn - vb->start_pfn + 1; + nr_pfn = roundup(nr_pfn, BITS_PER_LONG); + nr_used_bmap = nr_pfn / PFNS_PER_BMAP; + bmap_len = nr_pfn / BITS_PER_BYTE; + nr_buf = nr_used_bmap + 1; + + /* cmd, reserved and req_id are init to 0, unused here */ + hdr->page_shift = cpu_to_virtio16(vb->vdev, PAGE_SHIFT); + hdr->start_pfn = cpu_to_virtio64(vb->vdev, vb->start_pfn); + hdr->bmap_len = cpu_to_virtio64(vb->vdev, bmap_len); + sg_init_table(sg2, nr_buf); + sg_set_buf(&sg2[0], hdr, sizeof(struct balloon_bmap_hdr)); + for (i = 0; i < nr_used_bmap; i++) { + unsigned int buf_len = BALLOON_BMAP_SIZE; + + if (i + 1 == nr_used_bmap) + buf_len = bmap_len - BALLOON_BMAP_SIZE * i; + sg_set_buf(&sg2[i + 1], vb->page_bitmap[i], buf_len); + } - sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); + while (vq->num_free < nr_buf) + msleep(2); + if (virtqueue_add_outbuf(vq, sg2, nr_buf, vb, GFP_KERNEL) == 0) + virtqueue_kick(vq); - /* We should always be able to add one buffer to an empty queue. */ - virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); - virtqueue_kick(vq); + } else { + sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); + + /* We should always be able to add one buffer to an empty + * queue. */ + virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); + virtqueue_kick(vq); + } /* When host has read buffer, this completes via balloon_ack */ wait_event(vb->acked, virtqueue_get_buf(vq, &len)); @@ -138,13 +199,93 @@ static void set_page_pfns(struct virtio_balloon *vb, page_to_balloon_pfn(page) + i); } -static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) +static void extend_page_bitmap(struct virtio_balloon *vb) +{ + int i; + unsigned long bmap_len, bmap_count; + + bmap_len = ALIGN(get_max_pfn(), BITS_PER_LONG) / BITS_PER_BYTE; + bmap_count = bmap_len / BALLOON_BMAP_SIZE; + if (bmap_len % BALLOON_BMAP_SIZE) + bmap_count++; + if (bmap_count > BALLOON_BMAP_COUNT) + bmap_count = BALLOON_BMAP_COUNT; + + for (i = 1; i < bmap_count; i++) { + vb->page_bitmap[i] = kmalloc(BALLOON_BMAP_SIZE, GFP_ATOMIC); + if (vb->page_bitmap[i]) + vb->nr_page_bmap++; + else + break; + } +} + +static void kfree_page_bitmap(struct virtio_balloon *vb) +{ + int i; + + for (i = 0; i < vb->nr_page_bmap; i++) + kfree(vb->page_bitmap[i]); +} + +static void clear_page_bitmap(struct virtio_balloon *vb) +{ + int i; + + for (i = 0; i < vb->nr_page_bmap; i++) + memset(vb->page_bitmap[i], 0, BALLOON_BMAP_SIZE); +} + +static void set_page_bitmap(struct virtio_balloon *vb, + struct list_head *pages, struct virtqueue *vq) +{ + unsigned long pfn, pfn_limit; + struct page *page; + bool found; + int bmap_idx; + + vb->min_pfn = rounddown(vb->min_pfn, BITS_PER_LONG); + vb->max_pfn = roundup(vb->max_pfn, BITS_PER_LONG); + pfn_limit = PFNS_PER_BMAP * vb->nr_page_bmap; + + for (pfn = vb->min_pfn; pfn < vb->max_pfn; pfn += pfn_limit) { + unsigned long end_pfn; + + clear_page_bitmap(vb); + vb->start_pfn = pfn; + end_pfn = pfn; + found = false; + list_for_each_entry(page, pages, lru) { + unsigned long pos, balloon_pfn; + + balloon_pfn = page_to_balloon_pfn(page); + if (balloon_pfn < pfn || balloon_pfn >= pfn + pfn_limit) + continue; + bmap_idx = (balloon_pfn - pfn) / PFNS_PER_BMAP; + pos = (balloon_pfn - pfn) % PFNS_PER_BMAP; + set_bit(pos, vb->page_bitmap[bmap_idx]); + if (balloon_pfn > end_pfn) + end_pfn = balloon_pfn; + found = true; + } + if (found) { + vb->end_pfn = end_pfn; + tell_host(vb, vq); + } + } +} + +static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num, + bool use_bmap) { struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; - unsigned num_allocated_pages; + unsigned int num_allocated_pages; - /* We can only do one array worth at a time. */ - num = min(num, ARRAY_SIZE(vb->pfns)); + if (use_bmap) + init_pfn_range(vb); + else + /* We can only do one array worth at a time. */ + num = min(num, ARRAY_SIZE(vb->pfns)); mutex_lock(&vb->balloon_lock); for (vb->num_pfns = 0; vb->num_pfns < num; @@ -159,7 +300,10 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) msleep(200); break; } - set_page_pfns(vb, vb->pfns + vb->num_pfns, page); + if (use_bmap) + update_pfn_range(vb, page); + else + set_page_pfns(vb, vb->pfns + vb->num_pfns, page); vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) @@ -168,8 +312,13 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) num_allocated_pages = vb->num_pfns; /* Did we get any? */ - if (vb->num_pfns != 0) - tell_host(vb, vb->inflate_vq); + if (vb->num_pfns != 0) { + if (use_bmap) + set_page_bitmap(vb, &vb_dev_info->pages, + vb->inflate_vq); + else + tell_host(vb, vb->inflate_vq); + } mutex_unlock(&vb->balloon_lock); return num_allocated_pages; @@ -189,15 +338,19 @@ static void release_pages_balloon(struct virtio_balloon *vb, } } -static unsigned leak_balloon(struct virtio_balloon *vb, size_t num) +static unsigned int leak_balloon(struct virtio_balloon *vb, size_t num, + bool use_bmap) { - unsigned num_freed_pages; + unsigned int num_freed_pages; struct page *page; struct balloon_dev_info *vb_dev_info = &vb->vb_dev_info; LIST_HEAD(pages); - /* We can only do one array worth at a time. */ - num = min(num, ARRAY_SIZE(vb->pfns)); + if (use_bmap) + init_pfn_range(vb); + else + /* We can only do one array worth at a time. */ + num = min(num, ARRAY_SIZE(vb->pfns)); mutex_lock(&vb->balloon_lock); /* We can't release more pages than taken */ @@ -207,7 +360,10 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num) page = balloon_page_dequeue(vb_dev_info); if (!page) break; - set_page_pfns(vb, vb->pfns + vb->num_pfns, page); + if (use_bmap) + update_pfn_range(vb, page); + else + set_page_pfns(vb, vb->pfns + vb->num_pfns, page); list_add(&page->lru, &pages); vb->num_pages -= VIRTIO_BALLOON_PAGES_PER_PAGE; } @@ -218,8 +374,14 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num) * virtio_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST); * is true, we *have* to do it in this order */ - if (vb->num_pfns != 0) - tell_host(vb, vb->deflate_vq); + if (vb->num_pfns != 0) { + if (use_bmap) + set_page_bitmap(vb, &pages, vb->deflate_vq); + else + tell_host(vb, vb->deflate_vq); + + release_pages_balloon(vb, &pages); + } release_pages_balloon(vb, &pages); mutex_unlock(&vb->balloon_lock); return num_freed_pages; @@ -354,13 +516,15 @@ static int virtballoon_oom_notify(struct notifier_block *self, struct virtio_balloon *vb; unsigned long *freed; unsigned num_freed_pages; + bool use_bmap; vb = container_of(self, struct virtio_balloon, nb); if (!virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) return NOTIFY_OK; freed = parm; - num_freed_pages = leak_balloon(vb, oom_pages); + use_bmap = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_PAGE_BITMAP); + num_freed_pages = leak_balloon(vb, oom_pages, use_bmap); update_balloon_size(vb); *freed += num_freed_pages; @@ -380,15 +544,19 @@ static void update_balloon_size_func(struct work_struct *work) { struct virtio_balloon *vb; s64 diff; + bool use_bmap; vb = container_of(work, struct virtio_balloon, update_balloon_size_work); diff = towards_target(vb); + use_bmap = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_PAGE_BITMAP); + if (use_bmap && diff && vb->nr_page_bmap == 1) + extend_page_bitmap(vb); if (diff > 0) - diff -= fill_balloon(vb, diff); + diff -= fill_balloon(vb, diff, use_bmap); else if (diff < 0) - diff += leak_balloon(vb, -diff); + diff += leak_balloon(vb, -diff, use_bmap); update_balloon_size(vb); if (diff) @@ -533,6 +701,17 @@ static int virtballoon_probe(struct virtio_device *vdev) spin_lock_init(&vb->stop_update_lock); vb->stop_update = false; vb->num_pages = 0; + vb->bmap_hdr = kzalloc(sizeof(struct balloon_bmap_hdr), GFP_KERNEL); + /* Clear the feature bit if memory allocation fails */ + if (!vb->bmap_hdr) + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_BITMAP); + else { + vb->page_bitmap[0] = kmalloc(BALLOON_BMAP_SIZE, GFP_KERNEL); + if (!vb->page_bitmap[0]) + __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_BITMAP); + else + vb->nr_page_bmap = 1; + } mutex_init(&vb->balloon_lock); init_waitqueue_head(&vb->acked); vb->vdev = vdev; @@ -583,9 +762,12 @@ out: static void remove_common(struct virtio_balloon *vb) { + bool use_bmap; + + use_bmap = virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_PAGE_BITMAP); /* There might be pages left in the balloon: free them. */ while (vb->num_pages) - leak_balloon(vb, vb->num_pages); + leak_balloon(vb, vb->num_pages, use_bmap); update_balloon_size(vb); /* Now we reset the device so we can clean up the queues. */ @@ -609,6 +791,8 @@ static void virtballoon_remove(struct virtio_device *vdev) remove_common(vb); if (vb->vb_dev_info.inode) iput(vb->vb_dev_info.inode); + kfree_page_bitmap(vb); + kfree(vb->bmap_hdr); kfree(vb); } @@ -647,6 +831,7 @@ static unsigned int features[] = { VIRTIO_BALLOON_F_MUST_TELL_HOST, VIRTIO_BALLOON_F_STATS_VQ, VIRTIO_BALLOON_F_DEFLATE_ON_OOM, + VIRTIO_BALLOON_F_PAGE_BITMAP, }; static struct virtio_driver virtio_balloon_driver = {