On 6/3/19 6:38 PM, Alexander Duyck wrote: > On Mon, Jun 3, 2019 at 10:04 AM Nitesh Narayan Lal wrote: >> Enables the kernel to negotiate VIRTIO_BALLOON_F_HINTING feature with the >> host. If it is available and page_hinting_flag is set to true, page_hinting >> is enabled and its callbacks are configured along with the max_pages count >> which indicates the maximum number of pages that can be isolated and hinted >> at a time. Currently, only free pages of order >= (MAX_ORDER - 2) are >> reported. To prevent any false OOM max_pages count is set to 16. >> >> By default page_hinting feature is enabled and gets loaded as soon >> as the virtio-balloon driver is loaded. However, it could be disabled >> by writing the page_hinting_flag which is a virtio-balloon parameter. >> >> Signed-off-by: Nitesh Narayan Lal >> --- >> drivers/virtio/virtio_balloon.c | 112 +++++++++++++++++++++++++++- >> include/uapi/linux/virtio_balloon.h | 14 ++++ >> 2 files changed, 125 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c >> index f19061b585a4..40f09ea31643 100644 >> --- a/drivers/virtio/virtio_balloon.c >> +++ b/drivers/virtio/virtio_balloon.c >> @@ -31,6 +31,7 @@ >> #include >> #include >> #include >> +#include >> >> /* >> * Balloon device works in 4K page units. So each page is pointed to by >> @@ -48,6 +49,7 @@ >> /* The size of a free page block in bytes */ >> #define VIRTIO_BALLOON_FREE_PAGE_SIZE \ >> (1 << (VIRTIO_BALLOON_FREE_PAGE_ORDER + PAGE_SHIFT)) >> +#define VIRTIO_BALLOON_PAGE_HINTING_MAX_PAGES 16 >> >> #ifdef CONFIG_BALLOON_COMPACTION >> static struct vfsmount *balloon_mnt; >> @@ -58,6 +60,7 @@ enum virtio_balloon_vq { >> VIRTIO_BALLOON_VQ_DEFLATE, >> VIRTIO_BALLOON_VQ_STATS, >> VIRTIO_BALLOON_VQ_FREE_PAGE, >> + VIRTIO_BALLOON_VQ_HINTING, >> VIRTIO_BALLOON_VQ_MAX >> }; >> >> @@ -67,7 +70,8 @@ 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, >> + *hinting_vq; >> >> /* Balloon's own wq for cpu-intensive work items */ >> struct workqueue_struct *balloon_wq; >> @@ -125,6 +129,9 @@ struct virtio_balloon { >> >> /* To register a shrinker to shrink memory upon memory pressure */ >> struct shrinker shrinker; >> + >> + /* object pointing at the array of isolated pages ready for hinting */ >> + struct hinting_data *hinting_arr; > Just make this an array of size VIRTIO_BALLOON_PAGE_HINTING_MAX_PAGES. > It will save a bunch of complexity later. Make sense. >> }; >> >> static struct virtio_device_id id_table[] = { >> @@ -132,6 +139,85 @@ static struct virtio_device_id id_table[] = { >> { 0 }, >> }; >> >> +#ifdef CONFIG_PAGE_HINTING > Instead of having CONFIG_PAGE_HINTING enable this, maybe we should > have virtio-balloon enable CONFIG_PAGE_HINTING. > >> +struct virtio_balloon *hvb; >> +bool page_hinting_flag = true; >> +module_param(page_hinting_flag, bool, 0444); >> +MODULE_PARM_DESC(page_hinting_flag, "Enable page hinting"); >> + >> +static bool virtqueue_kick_sync(struct virtqueue *vq) >> +{ >> + u32 len; >> + >> + if (likely(virtqueue_kick(vq))) { >> + while (!virtqueue_get_buf(vq, &len) && >> + !virtqueue_is_broken(vq)) >> + cpu_relax(); >> + return true; > Is this a synchronous setup? Yes. > It seems kind of wasteful to have a > thread busy waiting here like this. It might make more sense to just > make this work like the other balloon queues and have a wait event > with a wake up in the interrupt handler for the queue. I can do that. I may have to use a flag or something else to page_hinting.c as well to ensure that no other bitmap scanning is initiated until then. > >> + } >> + return false; >> +} >> + >> +static void page_hinting_report(int entries) >> +{ >> + struct scatterlist sg; >> + struct virtqueue *vq = hvb->hinting_vq; >> + int err = 0; >> + struct hinting_data *hint_req; >> + u64 gpaddr; >> + >> + hint_req = kmalloc(sizeof(*hint_req), GFP_KERNEL); >> + if (!hint_req) >> + return; > Why do we need another allocation here? Couldn't you just allocate > hint_req on the stack and then use that? I think we might be doing too > much here. All this really needs to look like is something along the > lines of tell_host() minus the wait_event. > >> + gpaddr = virt_to_phys(hvb->hinting_arr); >> + hint_req->phys_addr = cpu_to_virtio64(hvb->vdev, gpaddr); >> + hint_req->size = cpu_to_virtio32(hvb->vdev, entries); >> + sg_init_one(&sg, hint_req, sizeof(*hint_req)); >> + err = virtqueue_add_outbuf(vq, &sg, 1, hint_req, GFP_KERNEL); >> + if (!err) >> + virtqueue_kick_sync(hvb->hinting_vq); >> + >> + kfree(hint_req); >> +} >> + >> +int page_hinting_prepare(void) >> +{ >> + hvb->hinting_arr = kmalloc_array(VIRTIO_BALLOON_PAGE_HINTING_MAX_PAGES, >> + sizeof(*hvb->hinting_arr), GFP_KERNEL); >> + if (!hvb->hinting_arr) >> + return -ENOMEM; >> + return 0; >> +} >> + > Why make the hinting_arr a dynamic allocation? You should probably > just make it a static array within the virtio_balloon structure. Then > you don't have the risk of an allocation failing and messing up the > hints. I agree. >> +void hint_pages(struct list_head *pages) >> +{ >> + struct page *page, *next; >> + unsigned long pfn; >> + int idx = 0, order; >> + >> + list_for_each_entry_safe(page, next, pages, lru) { >> + pfn = page_to_pfn(page); >> + order = page_private(page); >> + hvb->hinting_arr[idx].phys_addr = pfn << PAGE_SHIFT; >> + hvb->hinting_arr[idx].size = (1 << order) * PAGE_SIZE; >> + idx++; >> + } >> + page_hinting_report(idx); >> +} >> + > Getting back to my suggestion from earlier today. It might make sense > to not bother with the PAGE_SHIFT or PAGE_SIZE multiplication if you > just record everything in VIRTIO_BALLOON_PAGES intead of using the > actual address and size. > >> +void page_hinting_cleanup(void) >> +{ >> + kfree(hvb->hinting_arr); >> +} >> + > Same comment here. Make this array a part of virtio_balloon and you > don't have to free it. +1 > >> +static const struct page_hinting_cb hcb = { >> + .prepare = page_hinting_prepare, >> + .hint_pages = hint_pages, >> + .cleanup = page_hinting_cleanup, >> + .max_pages = VIRTIO_BALLOON_PAGE_HINTING_MAX_PAGES, >> +}; > With the above changes prepare and cleanup can be dropped. > >> +#endif >> + >> static u32 page_to_balloon_pfn(struct page *page) >> { >> unsigned long pfn = page_to_pfn(page); >> @@ -488,6 +574,7 @@ static int init_vqs(struct virtio_balloon *vb) >> names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate"; >> names[VIRTIO_BALLOON_VQ_STATS] = NULL; >> names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; >> + names[VIRTIO_BALLOON_VQ_HINTING] = NULL; >> >> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { >> names[VIRTIO_BALLOON_VQ_STATS] = "stats"; >> @@ -499,11 +586,18 @@ static int init_vqs(struct virtio_balloon *vb) >> callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL; >> } >> >> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) { >> + names[VIRTIO_BALLOON_VQ_HINTING] = "hinting_vq"; >> + callbacks[VIRTIO_BALLOON_VQ_HINTING] = NULL; >> + } >> err = vb->vdev->config->find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, >> vqs, callbacks, names, NULL, NULL); >> if (err) >> return err; >> >> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) >> + vb->hinting_vq = vqs[VIRTIO_BALLOON_VQ_HINTING]; >> + >> vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE]; >> vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE]; >> if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) { >> @@ -942,6 +1036,14 @@ static int virtballoon_probe(struct virtio_device *vdev) >> if (err) >> goto out_del_balloon_wq; >> } >> + >> +#ifdef CONFIG_PAGE_HINTING >> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING) && >> + page_hinting_flag) { >> + hvb = vb; >> + page_hinting_enable(&hcb); >> + } >> +#endif >> virtio_device_ready(vdev); >> >> if (towards_target(vb)) >> @@ -989,6 +1091,12 @@ static void virtballoon_remove(struct virtio_device *vdev) >> destroy_workqueue(vb->balloon_wq); >> } >> >> +#ifdef CONFIG_PAGE_HINTING >> + if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_HINTING)) { >> + hvb = NULL; >> + page_hinting_disable(); >> + } >> +#endif >> remove_common(vb); >> #ifdef CONFIG_BALLOON_COMPACTION >> if (vb->vb_dev_info.inode) >> @@ -1043,8 +1151,10 @@ static unsigned int features[] = { >> VIRTIO_BALLOON_F_MUST_TELL_HOST, >> VIRTIO_BALLOON_F_STATS_VQ, >> VIRTIO_BALLOON_F_DEFLATE_ON_OOM, >> + VIRTIO_BALLOON_F_HINTING, >> VIRTIO_BALLOON_F_FREE_PAGE_HINT, >> VIRTIO_BALLOON_F_PAGE_POISON, >> + VIRTIO_BALLOON_F_HINTING, >> }; >> >> static struct virtio_driver virtio_balloon_driver = { >> diff --git a/include/uapi/linux/virtio_balloon.h b/include/uapi/linux/virtio_balloon.h >> index a1966cd7b677..25e4f817c660 100644 >> --- a/include/uapi/linux/virtio_balloon.h >> +++ b/include/uapi/linux/virtio_balloon.h >> @@ -29,6 +29,7 @@ >> #include >> #include >> #include >> +#include >> >> /* The feature bitmap for virtio balloon */ >> #define VIRTIO_BALLOON_F_MUST_TELL_HOST 0 /* Tell before reclaiming pages */ >> @@ -36,6 +37,7 @@ >> #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_HINTING 5 /* Page hinting virtqueue */ >> >> /* Size of a PFN in the balloon interface. */ >> #define VIRTIO_BALLOON_PFN_SHIFT 12 >> @@ -108,4 +110,16 @@ struct virtio_balloon_stat { >> __virtio64 val; >> } __attribute__((packed)); >> >> +#ifdef CONFIG_PAGE_HINTING >> +/* >> + * struct hinting_data- holds the information associated with hinting. >> + * @phys_add: physical address associated with a page or the array holding >> + * the array of isolated pages. >> + * @size: total size associated with the phys_addr. >> + */ >> +struct hinting_data { >> + __virtio64 phys_addr; >> + __virtio32 size; >> +}; > So in order to avoid errors this should either have > "__attribute__((packed))" added or it should be changed to a pair of > u32 or u64 values so that it will always be the same size regardless > of what platform it is built on. I will take a look at this. Thanks. >> +#endif >> #endif /* _LINUX_VIRTIO_BALLOON_H */ >> -- >> 2.21.0 >> -- Regards Nitesh