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[79.182.20.254]) by smtp.gmail.com with ESMTPSA id t2sm2145055wml.30.2020.03.26.00.07.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Mar 2020 00:07:48 -0700 (PDT) Date: Thu, 26 Mar 2020 03:07:45 -0400 From: "Michael S. Tsirkin" To: teawater Cc: Hui Zhu , jasowang@redhat.com, akpm@linux-foundation.org, pagupta@redhat.com, mojha@codeaurora.org, david@redhat.com, namit@vmware.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org Subject: Re: [RFC for QEMU] virtio-balloon: Add option thp-order to set VIRTIO_BALLOON_F_THP_ORDER Message-ID: <20200326030636-mutt-send-email-mst@kernel.org> References: <1583999395-9131-1-git-send-email-teawater@gmail.com> <1583999395-9131-2-git-send-email-teawater@gmail.com> <20200312042340-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 17, 2020 at 06:13:32PM +0800, teawater wrote: > > > > 2020年3月12日 16:25，Michael S. Tsirkin 写道： > > > > On Thu, Mar 12, 2020 at 03:49:55PM +0800, Hui Zhu wrote: > >> If the guest kernel has many fragmentation pages, use virtio_balloon > >> will split THP of QEMU when it calls MADV_DONTNEED madvise to release > >> the balloon pages. > >> Set option thp-order to on will open flags VIRTIO_BALLOON_F_THP_ORDER. > >> It will set balloon size to THP size to handle the THP split issue. > >> > >> Signed-off-by: Hui Zhu > > > > What's wrong with just using the PartiallyBalloonedPage machinery > > instead? That would make it guest transparent. > > In balloon_inflate_page: > rb_page_size = qemu_ram_pagesize(rb); > > if (rb_page_size == BALLOON_PAGE_SIZE) { > /* Easy case */ > > It seems that PartiallyBalloonedPage is only used when rb_page_size is greater than BALLOON_PAGE_SIZE. > Do you mean I should modify the working mechanism of balloon_inflate_page function? > > Thanks, > Hui Yes, we can tweak it to unconditionally combine pages to a huge page. > > > >> --- > >> hw/virtio/virtio-balloon.c | 67 ++++++++++++++++--------- > >> include/standard-headers/linux/virtio_balloon.h | 4 ++ > >> 2 files changed, 47 insertions(+), 24 deletions(-) > >> > >> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > >> index a4729f7..cfe86b0 100644 > >> --- a/hw/virtio/virtio-balloon.c > >> +++ b/hw/virtio/virtio-balloon.c > >> @@ -340,37 +340,49 @@ static void virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq) > >> while (iov_to_buf(elem->out_sg, elem->out_num, offset, &pfn, 4) == 4) { > >> unsigned int p = virtio_ldl_p(vdev, &pfn); > >> hwaddr pa; > >> + size_t handle_size = BALLOON_PAGE_SIZE; > >> > >> pa = (hwaddr) p << VIRTIO_BALLOON_PFN_SHIFT; > >> offset += 4; > >> > >> - section = memory_region_find(get_system_memory(), pa, > >> - BALLOON_PAGE_SIZE); > >> - if (!section.mr) { > >> - trace_virtio_balloon_bad_addr(pa); > >> - continue; > >> - } > >> - if (!memory_region_is_ram(section.mr) || > >> - memory_region_is_rom(section.mr) || > >> - memory_region_is_romd(section.mr)) { > >> - trace_virtio_balloon_bad_addr(pa); > >> - memory_region_unref(section.mr); > >> - continue; > >> - } > >> + if (virtio_has_feature(s->host_features, > >> + VIRTIO_BALLOON_F_THP_ORDER)) > >> + handle_size = BALLOON_PAGE_SIZE << VIRTIO_BALLOON_THP_ORDER; > >> + > >> + while (handle_size > 0) { > >> + section = memory_region_find(get_system_memory(), pa, > >> + BALLOON_PAGE_SIZE); > >> + if (!section.mr) { > >> + trace_virtio_balloon_bad_addr(pa); > >> + continue; > >> + } > >> + if (!memory_region_is_ram(section.mr) || > >> + memory_region_is_rom(section.mr) || > >> + memory_region_is_romd(section.mr)) { > >> + trace_virtio_balloon_bad_addr(pa); > >> + memory_region_unref(section.mr); > >> + continue; > >> + } > >> > >> - trace_virtio_balloon_handle_output(memory_region_name(section.mr), > >> - pa); > >> - if (!qemu_balloon_is_inhibited()) { > >> - if (vq == s->ivq) { > >> - balloon_inflate_page(s, section.mr, > >> - section.offset_within_region, &pbp); > >> - } else if (vq == s->dvq) { > >> - balloon_deflate_page(s, section.mr, section.offset_within_region); > >> - } else { > >> - g_assert_not_reached(); > >> + trace_virtio_balloon_handle_output(memory_region_name(section.mr), > >> + pa); > >> + if (!qemu_balloon_is_inhibited()) { > >> + if (vq == s->ivq) { > >> + balloon_inflate_page(s, section.mr, > >> + section.offset_within_region, > >> + &pbp); > >> + } else if (vq == s->dvq) { > >> + balloon_deflate_page(s, section.mr, > >> + section.offset_within_region); > >> + } else { > >> + g_assert_not_reached(); > >> + } > >> } > >> + memory_region_unref(section.mr); > >> + > >> + pa += BALLOON_PAGE_SIZE; > >> + handle_size -= BALLOON_PAGE_SIZE; > >> } > >> - memory_region_unref(section.mr); > >> } > >> > >> virtqueue_push(vq, elem, offset); > >> @@ -693,6 +705,8 @@ static void virtio_balloon_set_config(VirtIODevice *vdev, > >> > >> memcpy(&config, config_data, virtio_balloon_config_size(dev)); > >> dev->actual = le32_to_cpu(config.actual); > >> + if (virtio_has_feature(vdev->host_features, VIRTIO_BALLOON_F_THP_ORDER)) > >> + dev->actual <<= VIRTIO_BALLOON_THP_ORDER; > >> if (dev->actual != oldactual) { > >> qapi_event_send_balloon_change(vm_ram_size - > >> ((ram_addr_t) dev->actual << VIRTIO_BALLOON_PFN_SHIFT)); > >> @@ -728,6 +742,9 @@ static void virtio_balloon_to_target(void *opaque, ram_addr_t target) > >> } > >> if (target) { > >> dev->num_pages = (vm_ram_size - target) >> VIRTIO_BALLOON_PFN_SHIFT; > >> + if (virtio_has_feature(dev->host_features, > >> + VIRTIO_BALLOON_F_THP_ORDER)) > >> + dev->num_pages >>= VIRTIO_BALLOON_THP_ORDER; > >> virtio_notify_config(vdev); > >> } > >> trace_virtio_balloon_to_target(target, dev->num_pages); > >> @@ -916,6 +933,8 @@ static Property virtio_balloon_properties[] = { > >> VIRTIO_BALLOON_F_DEFLATE_ON_OOM, false), > >> DEFINE_PROP_BIT("free-page-hint", VirtIOBalloon, host_features, > >> VIRTIO_BALLOON_F_FREE_PAGE_HINT, false), > >> + DEFINE_PROP_BIT("thp-order", VirtIOBalloon, host_features, > >> + VIRTIO_BALLOON_F_THP_ORDER, false), > >> /* QEMU 4.0 accidentally changed the config size even when free-page-hint > >> * is disabled, resulting in QEMU 3.1 migration incompatibility. This > >> * property retains this quirk for QEMU 4.1 machine types. > >> diff --git a/include/standard-headers/linux/virtio_balloon.h b/include/standard-headers/linux/virtio_balloon.h > >> index 9375ca2..f54d613 100644 > >> --- a/include/standard-headers/linux/virtio_balloon.h > >> +++ b/include/standard-headers/linux/virtio_balloon.h > >> @@ -36,10 +36,14 @@ > >> #define VIRTIO_BALLOON_F_DEFLATE_ON_OOM 2 /* Deflate balloon on OOM */ > >> #define VIRTIO_BALLOON_F_FREE_PAGE_HINT 3 /* VQ to report free pages */ > >> #define VIRTIO_BALLOON_F_PAGE_POISON 4 /* Guest is using page poisoning */ > >> +#define VIRTIO_BALLOON_F_THP_ORDER 5 /* Set balloon page order to thp order */ > >> > >> /* Size of a PFN in the balloon interface. */ > >> #define VIRTIO_BALLOON_PFN_SHIFT 12 > >> > >> +/* The order of the balloon page */ > >> +#define VIRTIO_BALLOON_THP_ORDER 9 > >> + > >> #define VIRTIO_BALLOON_CMD_ID_STOP 0 > >> #define VIRTIO_BALLOON_CMD_ID_DONE 1 > >> struct virtio_balloon_config { > >> -- > >> 2.7.4