> 2020年3月26日 15:17，Michael S. Tsirkin <mst@xxxxxxxxxx> 写道： > > First, either QEMU or Linux version of any interface changes > should be copied to the virtio TC. > > : OK. > > > On Mon, Mar 23, 2020 at 12:04:56AM +0800, Hui Zhu wrote: >> The first version is in [1]. >> According to the comments from Michael and David, I updated the patch. >> 1. Added a separate vq inflate_cont_vq to transport inflate continuous >> pages. >> 2. Set all the pages in the continuous pages movable then they can be >> compaction. >> 3. Added a new element pages_order to virtio_balloon_config. It is the >> inflate pages order that is set by the QEMU. >> 4. If the balloon cannot get any continuous pages from the system. >> Go back to use the single page to fill the balloon. >> 5. Use balloon_pages_alloc to allocate the single page and continuous >> pages. Replace __GFP_NORETRY with __GFP_RETRY_MAYFAIL when allocating >> the continuous pages because it can increase the success rate of >> allocating large chunks of memory. >> >> Following is the introduction of the function. >> 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. >> This is an example in a VM with 1G memory 1CPU: >> // This is the THP number before VM execution in the host. >> // None use THP. >> cat /proc/meminfo | grep AnonHugePages: >> AnonHugePages: 0 kB >> >> // After VM start, use usemem >> // (https://git.kernel.org/pub/scm/linux/kernel/git/wfg/vm-scalability.git) >> // punch-holes function generates 400m fragmentation pages in the guest >> // kernel. >> usemem --punch-holes -s -1 800m & >> >> // This is the THP number after this command in the host. >> // Some THP is used by VM because usemem will access 800M memory >> // in the guest. >> cat /proc/meminfo | grep AnonHugePages: >> AnonHugePages: 976896 kB >> >> // Connect to the QEMU monitor, setup balloon, and set it size to 600M. >> (qemu) device_add virtio-balloon-pci,id=balloon1 >> (qemu) info balloon >> balloon: actual=1024 >> (qemu) balloon 600 >> (qemu) info balloon >> balloon: actual=600 >> >> // This is the THP number after inflate the balloon in the host. >> cat /proc/meminfo | grep AnonHugePages: >> AnonHugePages: 151552 kB >> >> THP number decreased more than 800M. >> The reason is usemem with punch-holes option will free every other >> page after allocation. Then 400M free memory inside the guest kernel >> is fragmentation pages. >> The guest kernel will use them to inflate the balloon. When these >> fragmentation pages are freed, THP will be split. >> >> This commit tries to handle this with add a new flag >> VIRTIO_BALLOON_VQ_INFLATE_CONT. >> When this flag is set, the balloon will try to use continuous pages >> inflate the balloon. And the pages order is set to THP order. >> Then THP pages will be freed together in the host. >> This is an example in a VM with 1G memory 1CPU: >> // This is the THP number before VM execution in the host. >> // None use THP. >> cat /proc/meminfo | grep AnonHugePages: >> AnonHugePages: 0 kB >> >> // After VM start, use usemem punch-holes function generates 400M >> // fragmentation pages in the guest kernel. >> usemem --punch-holes -s -1 800m & >> >> // This is the THP number after this command in the host. >> // Some THP is used by VM because usemem will access 800M memory >> // in the guest. >> cat /proc/meminfo | grep AnonHugePages: >> AnonHugePages: 976896 kB >> >> // Connect to the QEMU monitor, setup balloon, and set it size to 600M. >> (qemu) device_add virtio-balloon-pci,id=balloon1,cont-pages=on >> (qemu) info balloon >> balloon: actual=1024 >> (qemu) balloon 600 >> (qemu) info balloon >> balloon: actual=600 >> >> // This is the THP number after inflate the balloon in the host. >> cat /proc/meminfo | grep AnonHugePages: >> AnonHugePages: 610304 kB >> >> The THP number decreases 358M. This shows that >> VIRTIO_BALLOON_VQ_INFLATE_CONT can help handle the THP split issue. >> >> [1] https://lkml.org/lkml/2020/3/12/144 >> >> Signed-off-by: Hui Zhu <teawaterz@xxxxxxxxxxxxxxxxx> > > I'd like to repeat my original idea of doing large page allocations > unconditionally within guest. > If so, should it transfer the large page information using inflate_vq? > >> --- >> drivers/virtio/virtio_balloon.c | 78 ++++++++++++++++++++++++++++++------- >> include/linux/balloon_compaction.h | 9 ++++- >> include/uapi/linux/virtio_balloon.h | 3 ++ >> mm/balloon_compaction.c | 40 +++++++++++++++---- >> 4 files changed, 109 insertions(+), 21 deletions(-) >> >> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c >> index 341458f..fbd2b02f 100644 >> --- a/drivers/virtio/virtio_balloon.c >> +++ b/drivers/virtio/virtio_balloon.c >> @@ -47,6 +47,7 @@ enum virtio_balloon_vq { >> VIRTIO_BALLOON_VQ_DEFLATE, >> VIRTIO_BALLOON_VQ_STATS, >> VIRTIO_BALLOON_VQ_FREE_PAGE, >> + VIRTIO_BALLOON_VQ_INFLATE_CONT, >> VIRTIO_BALLOON_VQ_MAX >> }; >> >> @@ -56,7 +57,8 @@ enum virtio_balloon_config_read { >> >> struct virtio_balloon { >> struct virtio_device *vdev; >> - struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq; >> + struct virtqueue *inflate_vq, *deflate_vq, *stats_vq, *free_page_vq, >> + *inflate_cont_vq; >> >> /* Balloon's own wq for cpu-intensive work items */ >> struct workqueue_struct *balloon_wq; >> @@ -114,6 +116,12 @@ struct virtio_balloon { >> >> /* To register a shrinker to shrink memory upon memory pressure */ >> struct shrinker shrinker; >> + >> + /* Pages order if VIRTIO_BALLOON_F_CONT_PAGES is set. >> + * if VIRTIO_BALLOON_F_CONT_PAGES is not set, >> + * pages_order will be set to 0. >> + */ >> + __u32 pages_order; >> }; >> >> static struct virtio_device_id id_table[] = { >> @@ -169,10 +177,11 @@ 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 unsigned int fill_balloon_order(struct virtio_balloon *vb, size_t num, >> + unsigned int order) >> { >> - unsigned num_allocated_pages; >> - unsigned num_pfns; >> + unsigned int num_allocated_pages; >> + unsigned int num_pfns; >> struct page *page; >> LIST_HEAD(pages); >> >> @@ -181,12 +190,12 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) >> >> for (num_pfns = 0; num_pfns < num; >> num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE) { >> - struct page *page = balloon_page_alloc(); >> + struct page *page = balloon_pages_alloc(order); >> >> if (!page) { >> dev_info_ratelimited(&vb->vdev->dev, >> - "Out of puff! Can't get %u pages\n", >> - VIRTIO_BALLOON_PAGES_PER_PAGE); >> + "Out of puff! Can't get %u pages\n", >> + VIRTIO_BALLOON_PAGES_PER_PAGE << order); >> /* Sleep for at least 1/5 of a second before retry. */ >> msleep(200); >> break; >> @@ -200,25 +209,48 @@ static unsigned fill_balloon(struct virtio_balloon *vb, size_t num) >> vb->num_pfns = 0; >> >> while ((page = balloon_page_pop(&pages))) { >> - balloon_page_enqueue(&vb->vb_dev_info, page); >> + balloon_pages_enqueue(&vb->vb_dev_info, page, order); >> >> set_page_pfns(vb, vb->pfns + vb->num_pfns, page); >> - vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE; >> + vb->num_pages += VIRTIO_BALLOON_PAGES_PER_PAGE << order; >> if (!virtio_has_feature(vb->vdev, >> VIRTIO_BALLOON_F_DEFLATE_ON_OOM)) >> - adjust_managed_page_count(page, -1); >> + adjust_managed_page_count(page, -(1 << order)); >> vb->num_pfns += VIRTIO_BALLOON_PAGES_PER_PAGE; >> } >> >> - num_allocated_pages = vb->num_pfns; >> + num_allocated_pages = vb->num_pfns << order; >> /* Did we get any? */ >> - if (vb->num_pfns != 0) >> - tell_host(vb, vb->inflate_vq); >> + if (vb->num_pfns != 0) { >> + if (order) >> + tell_host(vb, vb->inflate_cont_vq); >> + else >> + tell_host(vb, vb->inflate_vq); >> + } >> mutex_unlock(&vb->balloon_lock); >> >> return num_allocated_pages; >> } >> >> +static unsigned int fill_balloon(struct virtio_balloon *vb, size_t num) >> +{ >> + unsigned int num_allocated_pages = 0; >> + >> + if (vb->pages_order) { >> + num_allocated_pages = fill_balloon_order(vb, num, >> + vb->pages_order); >> + if (!num_allocated_pages) >> + dev_info_ratelimited(&vb->vdev->dev, >> + "Fail get any continuous pages in order %u\n", >> + vb->pages_order); >> + } >> + >> + if (!num_allocated_pages) >> + num_allocated_pages = fill_balloon_order(vb, num, 0); >> + >> + return num_allocated_pages; >> +} >> + >> static void release_pages_balloon(struct virtio_balloon *vb, >> struct list_head *pages) >> { > > > Hmm no this is not what was previously suggested. David Hildenbrand proposed > starting with highest order and iterating until we reach 0. > And I proposed a new API to allocate some memory between min and max > orders. > > >> @@ -481,6 +513,8 @@ static int init_vqs(struct virtio_balloon *vb) >> names[VIRTIO_BALLOON_VQ_STATS] = NULL; >> callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; >> names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; >> + callbacks[VIRTIO_BALLOON_VQ_INFLATE_CONT] = NULL; >> + names[VIRTIO_BALLOON_VQ_INFLATE_CONT] = NULL; >> >> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { >> names[VIRTIO_BALLOON_VQ_STATS] = "stats"; >> @@ -492,6 +526,11 @@ static int init_vqs(struct virtio_balloon *vb) >> callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; >> } >> >> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CONT_PAGES)) { >> + names[VIRTIO_BALLOON_VQ_INFLATE_CONT] = "inflate_cont"; >> + callbacks[VIRTIO_BALLOON_VQ_INFLATE_CONT] = balloon_ack; >> + } >> + >> err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, >> vqs, callbacks, names, NULL, NULL); >> if (err) >> @@ -524,6 +563,10 @@ static int init_vqs(struct virtio_balloon *vb) >> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) >> vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE]; >> >> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CONT_PAGES)) >> + vb->inflate_cont_vq >> + = vqs[VIRTIO_BALLOON_VQ_INFLATE_CONT]; >> + >> return 0; >> } >> >> @@ -945,6 +988,14 @@ static int virtballoon_probe(struct virtio_device *vdev) >> if (err) >> goto out_del_balloon_wq; >> } >> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_CONT_PAGES)) { >> + virtio_cread(vb->vdev, struct virtio_balloon_config, >> + pages_order, &vb->pages_order); >> + if (!virtio_has_feature(vb->vdev, VIRTIO_F_VERSION_1)) >> + vb->pages_order >> + = le32_to_cpu((__force __le32)vb->pages_order); >> + } else >> + vb->pages_order = 0; >> virtio_device_ready(vdev); >> >> if (towards_target(vb)) >> @@ -1058,6 +1109,7 @@ static unsigned int features[] = { >> VIRTIO_BALLOON_F_DEFLATE_ON_OOM, >> VIRTIO_BALLOON_F_FREE_PAGE_HINT, >> VIRTIO_BALLOON_F_PAGE_POISON, >> + VIRTIO_BALLOON_F_CONT_PAGES, >> }; >> >> static struct virtio_driver virtio_balloon_driver = { >> diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h >> index 338aa27..8180bbf 100644 >> --- a/include/linux/balloon_compaction.h >> +++ b/include/linux/balloon_compaction.h >> @@ -60,15 +60,22 @@ struct balloon_dev_info { >> struct inode *inode; >> }; >> >> -extern struct page *balloon_page_alloc(void); >> +extern struct page *balloon_pages_alloc(unsigned int order); >> extern void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, >> struct page *page); >> +extern void balloon_pages_enqueue(struct balloon_dev_info *b_dev_info, >> + struct page *page, unsigned int order); >> extern struct page *balloon_page_dequeue(struct balloon_dev_info *b_dev_info); >> extern size_t balloon_page_list_enqueue(struct balloon_dev_info *b_dev_info, >> struct list_head *pages); >> extern size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, >> struct list_head *pages, size_t n_req_pages); >> >> +static inline struct page *balloon_page_alloc(void) >> +{ >> + return balloon_pages_alloc(0); >> +} >> + >> static inline void balloon_devinfo_init(struct balloon_dev_info *balloon) >> { >> balloon->isolated_pages = 0; >> diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h >> index a1966cd7..e21b0aa 100644 >> --- a/include/uapi/linux/virtio_balloon.h >> +++ b/include/uapi/linux/virtio_balloon.h >> @@ -36,6 +36,7 @@ >> #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_CONT_PAGES 5 /* VQ to report continuous pages */ >> >> /* Size of a PFN in the balloon interface. */ >> #define VIRTIO_BALLOON_PFN_SHIFT 12 >> @@ -51,6 +52,8 @@ struct virtio_balloon_config { >> __u32 free_page_report_cmd_id; >> /* Stores PAGE_POISON if page poisoning is in use */ >> __u32 poison_val; >> + /* Pages order if VIRTIO_BALLOON_F_CONT_PAGES is set */ >> + __u32 pages_order; >> }; >> >> #define VIRTIO_BALLOON_S_SWAP_IN 0 /* Amount of memory swapped in */ >> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c >> index 26de020..87df4b2 100644 >> --- a/mm/balloon_compaction.c >> +++ b/mm/balloon_compaction.c >> @@ -112,8 +112,8 @@ size_t balloon_page_list_dequeue(struct balloon_dev_info *b_dev_info, >> EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); >> >> /* >> - * balloon_page_alloc - allocates a new page for insertion into the balloon >> - * page list. >> + * balloon_pages_alloc - allocates a new page for insertion into the balloon >> + * page list. >> * >> * Driver must call this function to properly allocate a new balloon page. >> * Driver must call balloon_page_enqueue before definitively removing the page >> @@ -121,14 +121,21 @@ EXPORT_SYMBOL_GPL(balloon_page_list_dequeue); >> * >> * Return: struct page for the allocated page or NULL on allocation failure. >> */ >> -struct page *balloon_page_alloc(void) >> +struct page *balloon_pages_alloc(unsigned int order) >> { >> - struct page *page = alloc_page(balloon_mapping_gfp_mask() | >> - __GFP_NOMEMALLOC | __GFP_NORETRY | >> - __GFP_NOWARN); >> + gfp_t gfp_mask; >> + >> + if (order > 1) >> + gfp_mask = __GFP_RETRY_MAYFAIL; >> + else >> + gfp_mask = __GFP_NORETRY; >> + >> + struct page *page = alloc_pages(balloon_mapping_gfp_mask() | >> + gfp_mask | __GFP_NOMEMALLOC | >> + __GFP_NOWARN, order); >> return page; >> } >> -EXPORT_SYMBOL_GPL(balloon_page_alloc); >> +EXPORT_SYMBOL_GPL(balloon_pages_alloc); >> >> /* >> * balloon_page_enqueue - inserts a new page into the balloon page list. >> @@ -155,6 +162,25 @@ void balloon_page_enqueue(struct balloon_dev_info *b_dev_info, >> EXPORT_SYMBOL_GPL(balloon_page_enqueue); >> >> /* >> + * balloon_pages_enqueue - inserts continuous pages into the balloon page list. >> + */ >> +void balloon_pages_enqueue(struct balloon_dev_info *b_dev_info, >> + struct page *page, unsigned int order) >> +{ >> + unsigned long flags; >> + unsigned long pfn = page_to_pfn(page); >> + unsigned long last_pfn = pfn + (1 << order) - 1; >> + >> + spin_lock_irqsave(&b_dev_info->pages_lock, flags); >> + for (; pfn <= last_pfn; pfn++) { >> + page = pfn_to_page(pfn); >> + balloon_page_enqueue_one(b_dev_info, page); >> + } >> + spin_unlock_irqrestore(&b_dev_info->pages_lock, flags); >> +} >> +EXPORT_SYMBOL_GPL(balloon_pages_enqueue); >> + >> +/* >> * balloon_page_dequeue - removes a page from balloon's page list and returns >> * its address to allow the driver to release the page. >> * @b_dev_info: balloon device decriptor where we will grab a page from. >> -- >> 2.7.4
