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Re: [Qemu-devel] [PATCH v2] migration: skip sending ram pages released b
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From: |
Jitendra Kolhe |
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Subject: |
Re: [Qemu-devel] [PATCH v2] migration: skip sending ram pages released by virtio-balloon driver. |
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Date: |
Wed, 13 Apr 2016 16:24:55 +0530 |
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User-agent: |
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 |
On 4/10/2016 10:29 PM, Michael S. Tsirkin wrote:
> On Fri, Apr 01, 2016 at 04:38:28PM +0530, Jitendra Kolhe wrote:
>> On 3/29/2016 5:58 PM, Michael S. Tsirkin wrote:
>>> On Mon, Mar 28, 2016 at 09:46:05AM +0530, Jitendra Kolhe wrote:
>>>> While measuring live migration performance for qemu/kvm guest, it
>>>> was observed that the qemu doesn’t maintain any intelligence for the
>>>> guest ram pages which are released by the guest balloon driver and
>>>> treat such pages as any other normal guest ram pages. This has direct
>>>> impact on overall migration time for the guest which has released
>>>> (ballooned out) memory to the host.
>>>>
>>>> In case of large systems, where we can configure large guests with 1TB
>>>> and with considerable amount of memory release by balloon driver to the,
>>>> host the migration time gets worse.
>>>>
>>>> The solution proposed below is local only to qemu (and does not require
>>>> any modification to Linux kernel or any guest driver). We have verified
>>>> the fix for large guests =1TB on HPE Superdome X (which can support up
>>>> to 240 cores and 12TB of memory) and in case where 90% of memory is
>>>> released by balloon driver the migration time for an idle guests reduces
>>>> to ~600 sec's from ~1200 sec’s.
>>>>
>>>> Detail: During live migration, as part of 1st iteration in
>>>> ram_save_iterate()
>>>> -> ram_find_and_save_block () will try to migrate ram pages which are
>>>> released by vitrio-balloon driver as part of dynamic memory delete.
>>>> Even though the pages which are returned to the host by virtio-balloon
>>>> driver are zero pages, the migration algorithm will still end up
>>>> scanning the entire page ram_find_and_save_block() -> ram_save_page/
>>>> ram_save_compressed_page -> save_zero_page() -> is_zero_range(). We
>>>> also end-up sending some control information over network for these
>>>> page during migration. This adds to total migration time.
>>>>
>>>> The proposed fix, uses the existing bitmap infrastructure to create
>>>> a virtio-balloon bitmap. The bits in the bitmap represent a guest ram
>>>> page of size 1UL<< VIRTIO_BALLOON_PFN_SHIFT. The bitmap represents
>>>> entire guest ram memory till max configured memory. Guest ram pages
>>>> claimed by the virtio-balloon driver will be represented by 1 in the
>>>> bitmap. During live migration, each guest ram page (host VA offset)
>>>> is checked against the virtio-balloon bitmap, if the bit is set the
>>>> corresponding ram page will be excluded from scanning and sending
>>>> control information during migration. The bitmap is also migrated to
>>>> the target as part of every ram_save_iterate loop and after the
>>>> guest is stopped remaining balloon bitmap is migrated as part of
>>>> balloon driver save / load interface.
>>>
>>> Migrating the bitmap might help a chained migration case
>>> but will slow down the more typical case a bit.
>>> Make it optional?
>>>
>>>
>>
>> Disabling migration of balloon bitmap would disable the
>> optimization permanently for all other subsequent migrations.
>>
>> The current implementation sends offsets and lengths of 1s
>> in the bitmap. In cases where we see highly fragmented
>> bitmap which may add to the bitmap migration time, but still
>> it would be less compared to total migration time.
>>
>> Here are some values from my test setup for an idle guest
>> with 16GB memory ballooned down to 4GB memory (with no
>> ballooning operation in progress during migration).
>> - Total migration time without proposed patch set - ~7600ms
>> - Total migration time with proposed patch set - ~5700ms
>> . Adds overhead of testing against bitmap - ~320ms
>> . Adds overhead of sending the bitmap - ~1.6ms
>> - Saves zero page scan + protocol time - ~2348ms
>> We may see some higher pct for time taken to migrate bitmap
>> in case ballooning is in progress during migration.
>>
>> The patch does introduces an option to enable/disable
>> testing ram_addr against balloon bitmap during migration
>> (since that’s the major overhead), but we still end-up
>> migrating the bitmap by default.
>>
>>>>
>>>> With the proposed fix, the average migration time for an idle guest
>>>> with 1TB maximum memory and 64vCpus
>>>> - reduces from ~1200 secs to ~600 sec, with guest memory ballooned
>>>> down to 128GB (~10% of 1TB).
>>>> - reduces from ~1300 to ~1200 sec (7%), with guest memory ballooned
>>>> down to 896GB (~90% of 1TB),
>>>> - with no ballooning configured, we don’t expect to see any impact
>>>> on total migration time.
>>>>
>>>> The optimization gets temporarily disabled, if the balloon operation is
>>>> in progress. Since the optimization skips scanning and migrating control
>>>> information for ballooned out pages, we might skip guest ram pages in
>>>> cases where the guest balloon driver has freed the ram page to the guest
>>>> but not yet informed the host/qemu about the ram page
>>>> (VIRTIO_BALLOON_F_MUST_TELL_HOST). In such case with optimization, we
>>>> might skip migrating ram pages which the guest is using. Since this
>>>> problem is specific to balloon leak, we can restrict balloon operation in
>>>> progress check to only balloon leak operation in progress check.
>>>>
>>>> The optimization also get permanently disabled (for all subsequent
>>>> migrations) in case any of the migration uses postcopy capability. In case
>>>> of postcopy the balloon bitmap would be required to send after vm_stop,
>>>> which has significant impact on the downtime. Moreover, the applications
>>>> in the guest space won’t be actually faulting on the ram pages which are
>>>> already ballooned out, the proposed optimization will not show any
>>>> improvement in migration time during postcopy.
>>>
>>>
>>> I think this optimization can work for post copy with some
>>> modifications.
>>>
>>
>> So is there any way to migrate the bitmap without impacting
>> downtime before starting the vm on dest in case of post-copy?
>
> With balloon inflated pre-migration? Yes. Put bitmap in a ram block,
> and use post-copy on it: whenever you detect a fault, and before
> fetching it, look at bitmap. If the relevant page is not yet on
> destination, migrate it.
>
> But you can also inflate the balloon on destination, after migration.
>
Ok, will explore post-copy migration to send the bitmap and make it
available before or as part of user fault. Also need to check if there
are any consequences in case ballooning operation is in progress on
destination.
Can we extend support for post-copy in a different patch set? and use
current patch set to support other remaining protocols?
>> In which case we can migrate bitmap to dest so that subsequent
>> migrations which are not using post-copy can use the optimization.
>> In pre-copy case, most of the bitmap is migrated as a part of
>> ram_save_iterate(), thus having a minimal impact on downtime.
>>
>> I am still unclear on how the patch set will benefit post-migration
>> case as guest on the dest should never fault on ballooned out pages,
>> So we won’t be saving on zero page scan time?
>
> That too. But you seem to assume balloon stays inflated forever.
> It does not, and we currently fault when guest on dest takes page out
> of the balloon.
>
> Finally, if balloon is inflated after migration, not migrating
> the pages in balloon will skip scanning non-zero pages
> since pages on source are non-zero.
>
>>>
>>> For post-copy, when guest takes page out of the balloon,
>>> it notifies the host.
>>>
>>
>> Yes, this will help in maintaining balloon bitmap up-to-date.
>>
>>> This only happens when MUST_TELL_HOST feature has been
>>> negotiated but most guests do negotiate it nowdays.
>>> (It also seems that your code assumes MUST_TELL_HOST - I think
>>> you must check and disable the bitmap management otherwise).
>>>
>>> At that point we can mark page as migrated to avoid
>>> requesting it from source.
>>>
>>
>> qemu no longer seem to add MUST_TELL_HOST feature
>> to dev->host_features.
>> Unless qemu set’s the feature,
>> how can it be negotiated it with the guest.
>> virtio_vdev_has_feature(vdev, VIRTIO_BALLOON_F_MUST_TELL_HOST)
>> always returns false to me. Am I missing something here?
>
> It never did because it never cared. If you care, you
> can set it.
>
Great thanks, was doubting that VIRTIO_BALLOON_F_MUST_TELL_HOST
was not set for some reason. Will set the flag in qemu and ask
guest to share feature list based on which will enable/disable
the optimization.
>>
>> Latest linux guest balloon driver >= 3.0, have stopped
>> checking for MUST_TELL_HOST feature, but they implement
>> functionality as if the feature is set.
>>
>> To address cases where guest may start using pages before
>> host is aware of them, I am disabling the test against bitmap
>> If ballooning is in progress (during migration). (I think
>> we can restrict ballooning in progress check to balloon
>> deflate condition only?). This will make sure that the pages
>> will be migrated.
>>
>> Thanks,
>> - Jitendra
>
> I don't know what does "ballooning is in progress" mean. Pages can be
> taken out of the balloon cause of compaction at any time. I don't think
> piling up special-cases like that is a good idea, just ask guest
> to talk to you before using pages.
>
Sure, the special-case check would no longer be required after
introducing check for VIRTIO_BALLOON_F_MUST_TELL_HOST flag.
Will post patch set with these changes.
Thanks,
- Jitendra
>>>
>>>
>>>> Signed-off-by: Jitendra Kolhe <address@hidden>
>>>> ---
>>>> Changed in v2:
>>>> - Resolved compilation issue for qemu-user binaries in exec.c
>>>> - Localize balloon bitmap test to save_zero_page().
>>>> - Updated version string for newly added migration capability to 2.7.
>>>> - Made minor modifications to patch commit text.
>>>>
>>>> balloon.c | 253
>>>> ++++++++++++++++++++++++++++++++++++-
>>>> exec.c | 3 +
>>>> hw/virtio/virtio-balloon.c | 35 ++++-
>>>> include/hw/virtio/virtio-balloon.h | 1 +
>>>> include/migration/migration.h | 1 +
>>>> include/sysemu/balloon.h | 15 ++-
>>>> migration/migration.c | 9 ++
>>>> migration/ram.c | 31 ++++-
>>>> qapi-schema.json | 5 +-
>>>> 9 files changed, 341 insertions(+), 12 deletions(-)
>>>>
>>>> diff --git a/balloon.c b/balloon.c
>>>> index f2ef50c..1c2d228 100644
>>>> --- a/balloon.c
>>>> +++ b/balloon.c
>>>> @@ -33,11 +33,34 @@
>>>> #include "qmp-commands.h"
>>>> #include "qapi/qmp/qerror.h"
>>>> #include "qapi/qmp/qjson.h"
>>>> +#include "exec/ram_addr.h"
>>>> +#include "migration/migration.h"
>>>> +
>>>> +#define BALLOON_BITMAP_DISABLE_FLAG -1UL
>>>> +
>>>> +typedef enum {
>>>> + BALLOON_BITMAP_DISABLE_NONE = 1, /* Enabled */
>>>> + BALLOON_BITMAP_DISABLE_CURRENT,
>>>> + BALLOON_BITMAP_DISABLE_PERMANENT,
>>>> +} BalloonBitmapDisableState;
>>>>
>>>> static QEMUBalloonEvent *balloon_event_fn;
>>>> static QEMUBalloonStatus *balloon_stat_fn;
>>>> +static QEMUBalloonInProgress *balloon_in_progress_fn;
>>>> static void *balloon_opaque;
>>>> static bool balloon_inhibited;
>>>> +static unsigned long balloon_bitmap_pages;
>>>> +static unsigned int balloon_bitmap_pfn_shift;
>>>> +static QemuMutex balloon_bitmap_mutex;
>>>> +static bool balloon_bitmap_xfered;
>>>> +static unsigned long balloon_min_bitmap_offset;
>>>> +static unsigned long balloon_max_bitmap_offset;
>>>> +static BalloonBitmapDisableState balloon_bitmap_disable_state;
>>>> +
>>>> +static struct BitmapRcu {
>>>> + struct rcu_head rcu;
>>>> + unsigned long *bmap;
>>>> +} *balloon_bitmap_rcu;
>>>>
>>>> bool qemu_balloon_is_inhibited(void)
>>>> {
>>>> @@ -49,6 +72,21 @@ void qemu_balloon_inhibit(bool state)
>>>> balloon_inhibited = state;
>>>> }
>>>>
>>>> +void qemu_mutex_lock_balloon_bitmap(void)
>>>> +{
>>>> + qemu_mutex_lock(&balloon_bitmap_mutex);
>>>> +}
>>>> +
>>>> +void qemu_mutex_unlock_balloon_bitmap(void)
>>>> +{
>>>> + qemu_mutex_unlock(&balloon_bitmap_mutex);
>>>> +}
>>>> +
>>>> +void qemu_balloon_reset_bitmap_data(void)
>>>> +{
>>>> + balloon_bitmap_xfered = false;
>>>> +}
>>>> +
>>>> static bool have_balloon(Error **errp)
>>>> {
>>>> if (kvm_enabled() && !kvm_has_sync_mmu()) {
>>>> @@ -65,9 +103,12 @@ static bool have_balloon(Error **errp)
>>>> }
>>>>
>>>> int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
>>>> - QEMUBalloonStatus *stat_func, void *opaque)
>>>> + QEMUBalloonStatus *stat_func,
>>>> + QEMUBalloonInProgress *in_progress_func,
>>>> + void *opaque, int pfn_shift)
>>>> {
>>>> - if (balloon_event_fn || balloon_stat_fn || balloon_opaque) {
>>>> + if (balloon_event_fn || balloon_stat_fn ||
>>>> + balloon_in_progress_fn || balloon_opaque) {
>>>> /* We're already registered one balloon handler. How many can
>>>> * a guest really have?
>>>> */
>>>> @@ -75,17 +116,39 @@ int qemu_add_balloon_handler(QEMUBalloonEvent
>>>> *event_func,
>>>> }
>>>> balloon_event_fn = event_func;
>>>> balloon_stat_fn = stat_func;
>>>> + balloon_in_progress_fn = in_progress_func;
>>>> balloon_opaque = opaque;
>>>> +
>>>> + qemu_mutex_init(&balloon_bitmap_mutex);
>>>> + balloon_bitmap_disable_state = BALLOON_BITMAP_DISABLE_NONE;
>>>> + balloon_bitmap_pfn_shift = pfn_shift;
>>>> + balloon_bitmap_pages = (last_ram_offset() >>
>>>> balloon_bitmap_pfn_shift);
>>>> + balloon_bitmap_rcu = g_new0(struct BitmapRcu, 1);
>>>> + balloon_bitmap_rcu->bmap = bitmap_new(balloon_bitmap_pages);
>>>> + bitmap_clear(balloon_bitmap_rcu->bmap, 0, balloon_bitmap_pages);
>>>> +
>>>> return 0;
>>>> }
>>>>
>>>> +static void balloon_bitmap_free(struct BitmapRcu *bmap)
>>>> +{
>>>> + g_free(bmap->bmap);
>>>> + g_free(bmap);
>>>> +}
>>>> +
>>>> void qemu_remove_balloon_handler(void *opaque)
>>>> {
>>>> + struct BitmapRcu *bitmap = balloon_bitmap_rcu;
>>>> if (balloon_opaque != opaque) {
>>>> return;
>>>> }
>>>> + atomic_rcu_set(&balloon_bitmap_rcu, NULL);
>>>> + if (bitmap) {
>>>> + call_rcu(bitmap, balloon_bitmap_free, rcu);
>>>> + }
>>>> balloon_event_fn = NULL;
>>>> balloon_stat_fn = NULL;
>>>> + balloon_in_progress_fn = NULL;
>>>> balloon_opaque = NULL;
>>>> }
>>>>
>>>> @@ -116,3 +179,189 @@ void qmp_balloon(int64_t target, Error **errp)
>>>> trace_balloon_event(balloon_opaque, target);
>>>> balloon_event_fn(balloon_opaque, target);
>>>> }
>>>> +
>>>> +/* Handle Ram hotplug case, only called in case old < new */
>>>> +int qemu_balloon_bitmap_extend(ram_addr_t old, ram_addr_t new)
>>>> +{
>>>> + struct BitmapRcu *old_bitmap = balloon_bitmap_rcu, *bitmap;
>>>> + unsigned long old_offset, new_offset;
>>>> +
>>>> + if (!balloon_bitmap_rcu) {
>>>> + return -1;
>>>> + }
>>>> +
>>>> + old_offset = (old >> balloon_bitmap_pfn_shift);
>>>> + new_offset = (new >> balloon_bitmap_pfn_shift);
>>>> +
>>>> + bitmap = g_new(struct BitmapRcu, 1);
>>>> + bitmap->bmap = bitmap_new(new_offset);
>>>> +
>>>> + qemu_mutex_lock_balloon_bitmap();
>>>> + bitmap_clear(bitmap->bmap, 0,
>>>> + balloon_bitmap_pages + new_offset - old_offset);
>>>> + bitmap_copy(bitmap->bmap, old_bitmap->bmap, old_offset);
>>>> +
>>>> + atomic_rcu_set(&balloon_bitmap_rcu, bitmap);
>>>> + balloon_bitmap_pages += new_offset - old_offset;
>>>> + qemu_mutex_unlock_balloon_bitmap();
>>>> + call_rcu(old_bitmap, balloon_bitmap_free, rcu);
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> +/* Should be called with balloon bitmap mutex lock held */
>>>> +int qemu_balloon_bitmap_update(ram_addr_t addr, int deflate)
>>>> +{
>>>> + unsigned long *bitmap;
>>>> + unsigned long offset = 0;
>>>> +
>>>> + if (!balloon_bitmap_rcu) {
>>>> + return -1;
>>>> + }
>>>> + offset = (addr >> balloon_bitmap_pfn_shift);
>>>> + if (balloon_bitmap_xfered) {
>>>> + if (offset < balloon_min_bitmap_offset) {
>>>> + balloon_min_bitmap_offset = offset;
>>>> + }
>>>> + if (offset > balloon_max_bitmap_offset) {
>>>> + balloon_max_bitmap_offset = offset;
>>>> + }
>>>> + }
>>>> +
>>>> + rcu_read_lock();
>>>> + bitmap = atomic_rcu_read(&balloon_bitmap_rcu)->bmap;
>>>> + if (deflate == 0) {
>>>> + set_bit(offset, bitmap);
>>>> + } else {
>>>> + clear_bit(offset, bitmap);
>>>> + }
>>>> + rcu_read_unlock();
>>>> + return 0;
>>>> +}
>>>> +
>>>> +void qemu_balloon_bitmap_setup(void)
>>>> +{
>>>> + if (migrate_postcopy_ram()) {
>>>> + balloon_bitmap_disable_state = BALLOON_BITMAP_DISABLE_PERMANENT;
>>>> + } else if ((!balloon_bitmap_rcu || !migrate_skip_balloon()) &&
>>>> + (balloon_bitmap_disable_state !=
>>>> + BALLOON_BITMAP_DISABLE_PERMANENT)) {
>>>> + balloon_bitmap_disable_state = BALLOON_BITMAP_DISABLE_CURRENT;
>>>> + }
>>>> +}
>>>> +
>>>> +int qemu_balloon_bitmap_test(RAMBlock *rb, ram_addr_t addr)
>>>> +{
>>>> + unsigned long *bitmap;
>>>> + ram_addr_t base;
>>>> + unsigned long nr = 0;
>>>> + int ret = 0;
>>>> +
>>>> + if (balloon_bitmap_disable_state == BALLOON_BITMAP_DISABLE_CURRENT ||
>>>> + balloon_bitmap_disable_state == BALLOON_BITMAP_DISABLE_PERMANENT)
>>>> {
>>>> + return 0;
>>>> + }
>>>> + balloon_in_progress_fn(balloon_opaque, &ret);
>>>> + if (ret == 1) {
>>>> + return 0;
>>>> + }
>>>> +
>>>> + rcu_read_lock();
>>>> + bitmap = atomic_rcu_read(&balloon_bitmap_rcu)->bmap;
>>>> + base = rb->offset >> balloon_bitmap_pfn_shift;
>>>> + nr = base + (addr >> balloon_bitmap_pfn_shift);
>>>> + if (test_bit(nr, bitmap)) {
>>>> + ret = 1;
>>>> + }
>>>> + rcu_read_unlock();
>>>> + return ret;
>>>> +}
>>>> +
>>>> +int qemu_balloon_bitmap_save(QEMUFile *f)
>>>> +{
>>>> + unsigned long *bitmap;
>>>> + unsigned long offset = 0, next = 0, len = 0;
>>>> + unsigned long tmpoffset = 0, tmplimit = 0;
>>>> +
>>>> + if (balloon_bitmap_disable_state == BALLOON_BITMAP_DISABLE_PERMANENT)
>>>> {
>>>> + qemu_put_be64(f, BALLOON_BITMAP_DISABLE_FLAG);
>>>> + return 0;
>>>> + }
>>>> +
>>>> + qemu_mutex_lock_balloon_bitmap();
>>>> + if (balloon_bitmap_xfered) {
>>>> + tmpoffset = balloon_min_bitmap_offset;
>>>> + tmplimit = balloon_max_bitmap_offset;
>>>> + } else {
>>>> + balloon_bitmap_xfered = true;
>>>> + tmpoffset = offset;
>>>> + tmplimit = balloon_bitmap_pages;
>>>> + }
>>>> +
>>>> + balloon_min_bitmap_offset = balloon_bitmap_pages;
>>>> + balloon_max_bitmap_offset = 0;
>>>> +
>>>> + qemu_put_be64(f, balloon_bitmap_pages);
>>>> + qemu_put_be64(f, tmpoffset);
>>>> + qemu_put_be64(f, tmplimit);
>>>> + rcu_read_lock();
>>>> + bitmap = atomic_rcu_read(&balloon_bitmap_rcu)->bmap;
>>>> + while (tmpoffset < tmplimit) {
>>>> + unsigned long next_set_bit, start_set_bit;
>>>> + next_set_bit = find_next_bit(bitmap, balloon_bitmap_pages,
>>>> tmpoffset);
>>>> + start_set_bit = next_set_bit;
>>>> + if (next_set_bit == balloon_bitmap_pages) {
>>>> + len = 0;
>>>> + next = start_set_bit;
>>>> + qemu_put_be64(f, next);
>>>> + qemu_put_be64(f, len);
>>>> + break;
>>>> + }
>>>> + next_set_bit = find_next_zero_bit(bitmap,
>>>> + balloon_bitmap_pages,
>>>> + ++next_set_bit);
>>>> + len = (next_set_bit - start_set_bit);
>>>> + next = start_set_bit;
>>>> + qemu_put_be64(f, next);
>>>> + qemu_put_be64(f, len);
>>>> + tmpoffset = next + len;
>>>> + }
>>>> + rcu_read_unlock();
>>>> + qemu_mutex_unlock_balloon_bitmap();
>>>> + return 0;
>>>> +}
>>>> +
>>>> +int qemu_balloon_bitmap_load(QEMUFile *f)
>>>> +{
>>>> + unsigned long *bitmap;
>>>> + unsigned long next = 0, len = 0;
>>>> + unsigned long tmpoffset = 0, tmplimit = 0;
>>>> +
>>>> + if (!balloon_bitmap_rcu) {
>>>> + return -1;
>>>> + }
>>>> +
>>>> + qemu_mutex_lock_balloon_bitmap();
>>>> + balloon_bitmap_pages = qemu_get_be64(f);
>>>> + if (balloon_bitmap_pages == BALLOON_BITMAP_DISABLE_FLAG) {
>>>> + balloon_bitmap_disable_state = BALLOON_BITMAP_DISABLE_PERMANENT;
>>>> + qemu_mutex_unlock_balloon_bitmap();
>>>> + return 0;
>>>> + }
>>>> + tmpoffset = qemu_get_be64(f);
>>>> + tmplimit = qemu_get_be64(f);
>>>> + rcu_read_lock();
>>>> + bitmap = atomic_rcu_read(&balloon_bitmap_rcu)->bmap;
>>>> + while (tmpoffset < tmplimit) {
>>>> + next = qemu_get_be64(f);
>>>> + len = qemu_get_be64(f);
>>>> + if (len == 0) {
>>>> + break;
>>>> + }
>>>> + bitmap_set(bitmap, next, len);
>>>> + tmpoffset = next + len;
>>>> + }
>>>> + rcu_read_unlock();
>>>> + qemu_mutex_unlock_balloon_bitmap();
>>>> + return 0;
>>>> +}
>>>> diff --git a/exec.c b/exec.c
>>>> index f398d21..7a448e5 100644
>>>> --- a/exec.c
>>>> +++ b/exec.c
>>>> @@ -43,6 +43,7 @@
>>>> #else /* !CONFIG_USER_ONLY */
>>>> #include "sysemu/xen-mapcache.h"
>>>> #include "trace.h"
>>>> +#include "sysemu/balloon.h"
>>>> #endif
>>>> #include "exec/cpu-all.h"
>>>> #include "qemu/rcu_queue.h"
>>>> @@ -1610,6 +1611,8 @@ static void ram_block_add(RAMBlock *new_block, Error
>>>> **errp)
>>>> if (new_ram_size > old_ram_size) {
>>>> migration_bitmap_extend(old_ram_size, new_ram_size);
>>>> dirty_memory_extend(old_ram_size, new_ram_size);
>>>> + qemu_balloon_bitmap_extend(old_ram_size << TARGET_PAGE_BITS,
>>>> + new_ram_size << TARGET_PAGE_BITS);
>>>> }
>>>> /* Keep the list sorted from biggest to smallest block. Unlike
>>>> QTAILQ,
>>>> * QLIST (which has an RCU-friendly variant) does not have insertion
>>>> at
>>>> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
>>>> index 22ad25c..9f3a4c8 100644
>>>> --- a/hw/virtio/virtio-balloon.c
>>>> +++ b/hw/virtio/virtio-balloon.c
>>>> @@ -27,6 +27,7 @@
>>>> #include "qapi/visitor.h"
>>>> #include "qapi-event.h"
>>>> #include "trace.h"
>>>> +#include "migration/migration.h"
>>>>
>>>> #if defined(__linux__)
>>>> #include <sys/mman.h>
>>>> @@ -214,11 +215,13 @@ static void
>>>> virtio_balloon_handle_output(VirtIODevice *vdev, VirtQueue *vq)
>>>> VirtQueueElement *elem;
>>>> MemoryRegionSection section;
>>>>
>>>> + qemu_mutex_lock_balloon_bitmap();
>>>> for (;;) {
>>>> size_t offset = 0;
>>>> uint32_t pfn;
>>>> elem = virtqueue_pop(vq, sizeof(VirtQueueElement));
>>>> if (!elem) {
>>>> + qemu_mutex_unlock_balloon_bitmap();
>>>> return;
>>>> }
>>>>
>>>> @@ -242,6 +245,7 @@ static void virtio_balloon_handle_output(VirtIODevice
>>>> *vdev, VirtQueue *vq)
>>>> addr = section.offset_within_region;
>>>> balloon_page(memory_region_get_ram_ptr(section.mr) + addr,
>>>> !!(vq == s->dvq));
>>>> + qemu_balloon_bitmap_update(addr, !!(vq == s->dvq));
>>>> memory_region_unref(section.mr);
>>>> }
>>>>
>>>> @@ -249,6 +253,7 @@ static void virtio_balloon_handle_output(VirtIODevice
>>>> *vdev, VirtQueue *vq)
>>>> virtio_notify(vdev, vq);
>>>> g_free(elem);
>>>> }
>>>> + qemu_mutex_unlock_balloon_bitmap();
>>>> }
>>>>
>>>> static void virtio_balloon_receive_stats(VirtIODevice *vdev, VirtQueue
>>>> *vq)
>>>> @@ -303,6 +308,16 @@ out:
>>>> }
>>>> }
>>>>
>>>> +static void virtio_balloon_migration_state_changed(Notifier *notifier,
>>>> + void *data)
>>>> +{
>>>> + MigrationState *mig = data;
>>>> +
>>>> + if (migration_has_failed(mig)) {
>>>> + qemu_balloon_reset_bitmap_data();
>>>> + }
>>>> +}
>>>> +
>>>> static void virtio_balloon_get_config(VirtIODevice *vdev, uint8_t
>>>> *config_data)
>>>> {
>>>> VirtIOBalloon *dev = VIRTIO_BALLOON(vdev);
>>>> @@ -382,6 +397,16 @@ static void virtio_balloon_stat(void *opaque,
>>>> BalloonInfo *info)
>>>> VIRTIO_BALLOON_PFN_SHIFT);
>>>> }
>>>>
>>>> +static void virtio_balloon_in_progress(void *opaque, int *status)
>>>> +{
>>>> + VirtIOBalloon *dev = VIRTIO_BALLOON(opaque);
>>>> + if (cpu_to_le32(dev->actual) != cpu_to_le32(dev->num_pages)) {
>>>> + *status = 1;
>>>> + return;
>>>> + }
>>>> + *status = 0;
>>>> +}
>>>> +
>>>> static void virtio_balloon_to_target(void *opaque, ram_addr_t target)
>>>> {
>>>> VirtIOBalloon *dev = VIRTIO_BALLOON(opaque);
>>>> @@ -409,6 +434,7 @@ static void virtio_balloon_save_device(VirtIODevice
>>>> *vdev, QEMUFile *f)
>>>>
>>>> qemu_put_be32(f, s->num_pages);
>>>> qemu_put_be32(f, s->actual);
>>>> + qemu_balloon_bitmap_save(f);
>>>> }
>>>>
>>>> static int virtio_balloon_load(QEMUFile *f, void *opaque, int version_id)
>>>> @@ -426,6 +452,7 @@ static int virtio_balloon_load_device(VirtIODevice
>>>> *vdev, QEMUFile *f,
>>>>
>>>> s->num_pages = qemu_get_be32(f);
>>>> s->actual = qemu_get_be32(f);
>>>> + qemu_balloon_bitmap_load(f);
>>>> return 0;
>>>> }
>>>>
>>>> @@ -439,7 +466,9 @@ static void virtio_balloon_device_realize(DeviceState
>>>> *dev, Error **errp)
>>>> sizeof(struct virtio_balloon_config));
>>>>
>>>> ret = qemu_add_balloon_handler(virtio_balloon_to_target,
>>>> - virtio_balloon_stat, s);
>>>> + virtio_balloon_stat,
>>>> + virtio_balloon_in_progress, s,
>>>> + VIRTIO_BALLOON_PFN_SHIFT);
>>>>
>>>> if (ret < 0) {
>>>> error_setg(errp, "Only one balloon device is supported");
>>>> @@ -453,6 +482,9 @@ static void virtio_balloon_device_realize(DeviceState
>>>> *dev, Error **errp)
>>>>
>>>> reset_stats(s);
>>>>
>>>> + s->migration_state_notifier.notify =
>>>> virtio_balloon_migration_state_changed;
>>>> + add_migration_state_change_notifier(&s->migration_state_notifier);
>>>> +
>>>> register_savevm(dev, "virtio-balloon", -1, 1,
>>>> virtio_balloon_save, virtio_balloon_load, s);
>>>> }
>>>> @@ -462,6 +494,7 @@ static void
>>>> virtio_balloon_device_unrealize(DeviceState *dev, Error **errp)
>>>> VirtIODevice *vdev = VIRTIO_DEVICE(dev);
>>>> VirtIOBalloon *s = VIRTIO_BALLOON(dev);
>>>>
>>>> + remove_migration_state_change_notifier(&s->migration_state_notifier);
>>>> balloon_stats_destroy_timer(s);
>>>> qemu_remove_balloon_handler(s);
>>>> unregister_savevm(dev, "virtio-balloon", s);
>>>> diff --git a/include/hw/virtio/virtio-balloon.h
>>>> b/include/hw/virtio/virtio-balloon.h
>>>> index 35f62ac..1ded5a9 100644
>>>> --- a/include/hw/virtio/virtio-balloon.h
>>>> +++ b/include/hw/virtio/virtio-balloon.h
>>>> @@ -43,6 +43,7 @@ typedef struct VirtIOBalloon {
>>>> int64_t stats_last_update;
>>>> int64_t stats_poll_interval;
>>>> uint32_t host_features;
>>>> + Notifier migration_state_notifier;
>>>> } VirtIOBalloon;
>>>>
>>>> #endif
>>>> diff --git a/include/migration/migration.h b/include/migration/migration.h
>>>> index ac2c12c..6c1d1af 100644
>>>> --- a/include/migration/migration.h
>>>> +++ b/include/migration/migration.h
>>>> @@ -267,6 +267,7 @@ void migrate_del_blocker(Error *reason);
>>>>
>>>> bool migrate_postcopy_ram(void);
>>>> bool migrate_zero_blocks(void);
>>>> +bool migrate_skip_balloon(void);
>>>>
>>>> bool migrate_auto_converge(void);
>>>>
>>>> diff --git a/include/sysemu/balloon.h b/include/sysemu/balloon.h
>>>> index 3f976b4..5325c38 100644
>>>> --- a/include/sysemu/balloon.h
>>>> +++ b/include/sysemu/balloon.h
>>>> @@ -15,14 +15,27 @@
>>>> #define _QEMU_BALLOON_H
>>>>
>>>> #include "qapi-types.h"
>>>> +#include "migration/qemu-file.h"
>>>>
>>>> typedef void (QEMUBalloonEvent)(void *opaque, ram_addr_t target);
>>>> typedef void (QEMUBalloonStatus)(void *opaque, BalloonInfo *info);
>>>> +typedef void (QEMUBalloonInProgress) (void *opaque, int *status);
>>>>
>>>> int qemu_add_balloon_handler(QEMUBalloonEvent *event_func,
>>>> - QEMUBalloonStatus *stat_func, void *opaque);
>>>> + QEMUBalloonStatus *stat_func,
>>>> + QEMUBalloonInProgress *progress_func,
>>>> + void *opaque, int pfn_shift);
>>>> void qemu_remove_balloon_handler(void *opaque);
>>>> bool qemu_balloon_is_inhibited(void);
>>>> void qemu_balloon_inhibit(bool state);
>>>> +void qemu_mutex_lock_balloon_bitmap(void);
>>>> +void qemu_mutex_unlock_balloon_bitmap(void);
>>>> +void qemu_balloon_reset_bitmap_data(void);
>>>> +void qemu_balloon_bitmap_setup(void);
>>>> +int qemu_balloon_bitmap_extend(ram_addr_t old, ram_addr_t new);
>>>> +int qemu_balloon_bitmap_update(ram_addr_t addr, int deflate);
>>>> +int qemu_balloon_bitmap_test(RAMBlock *rb, ram_addr_t addr);
>>>> +int qemu_balloon_bitmap_save(QEMUFile *f);
>>>> +int qemu_balloon_bitmap_load(QEMUFile *f);
>>>>
>>>> #endif
>>>> diff --git a/migration/migration.c b/migration/migration.c
>>>> index 034a918..cb86307 100644
>>>> --- a/migration/migration.c
>>>> +++ b/migration/migration.c
>>>> @@ -1200,6 +1200,15 @@ int migrate_use_xbzrle(void)
>>>> return s->enabled_capabilities[MIGRATION_CAPABILITY_XBZRLE];
>>>> }
>>>>
>>>> +bool migrate_skip_balloon(void)
>>>> +{
>>>> + MigrationState *s;
>>>> +
>>>> + s = migrate_get_current();
>>>> +
>>>> + return s->enabled_capabilities[MIGRATION_CAPABILITY_SKIP_BALLOON];
>>>> +}
>>>> +
>>>> int64_t migrate_xbzrle_cache_size(void)
>>>> {
>>>> MigrationState *s;
>>>> diff --git a/migration/ram.c b/migration/ram.c
>>>> index 704f6a9..161ab73 100644
>>>> --- a/migration/ram.c
>>>> +++ b/migration/ram.c
>>>> @@ -40,6 +40,7 @@
>>>> #include "trace.h"
>>>> #include "exec/ram_addr.h"
>>>> #include "qemu/rcu_queue.h"
>>>> +#include "sysemu/balloon.h"
>>>>
>>>> #ifdef DEBUG_MIGRATION_RAM
>>>> #define DPRINTF(fmt, ...) \
>>>> @@ -65,6 +66,7 @@ static uint64_t bitmap_sync_count;
>>>> #define RAM_SAVE_FLAG_XBZRLE 0x40
>>>> /* 0x80 is reserved in migration.h start with 0x100 next */
>>>> #define RAM_SAVE_FLAG_COMPRESS_PAGE 0x100
>>>> +#define RAM_SAVE_FLAG_BALLOON 0x200
>>>>
>>>> static const uint8_t ZERO_TARGET_PAGE[TARGET_PAGE_SIZE];
>>>>
>>>> @@ -702,13 +704,17 @@ static int save_zero_page(QEMUFile *f, RAMBlock
>>>> *block, ram_addr_t offset,
>>>> {
>>>> int pages = -1;
>>>>
>>>> - if (is_zero_range(p, TARGET_PAGE_SIZE)) {
>>>> - acct_info.dup_pages++;
>>>> - *bytes_transferred += save_page_header(f, block,
>>>> + if (qemu_balloon_bitmap_test(block, offset) != 1) {
>>>> + if (is_zero_range(p, TARGET_PAGE_SIZE)) {
>>>> + acct_info.dup_pages++;
>>>> + *bytes_transferred += save_page_header(f, block,
>>>> offset |
>>>> RAM_SAVE_FLAG_COMPRESS);
>>>> - qemu_put_byte(f, 0);
>>>> - *bytes_transferred += 1;
>>>> - pages = 1;
>>>> + qemu_put_byte(f, 0);
>>>> + *bytes_transferred += 1;
>>>> + pages = 1;
>>>> + }
>>>> + } else {
>>>> + pages = 0;
>>>> }
>>>>
>>>> return pages;
>>>> @@ -773,7 +779,7 @@ static int ram_save_page(QEMUFile *f, PageSearchStatus
>>>> *pss,
>>>> * page would be stale
>>>> */
>>>> xbzrle_cache_zero_page(current_addr);
>>>> - } else if (!ram_bulk_stage && migrate_use_xbzrle()) {
>>>> + } else if (pages != 0 && !ram_bulk_stage && migrate_use_xbzrle())
>>>> {
>>>> pages = save_xbzrle_page(f, &p, current_addr, block,
>>>> offset, last_stage,
>>>> bytes_transferred);
>>>> if (!last_stage) {
>>>> @@ -1355,6 +1361,9 @@ static int ram_find_and_save_block(QEMUFile *f, bool
>>>> last_stage,
>>>> }
>>>>
>>>> if (found) {
>>>> + /* skip saving ram host page if the corresponding guest page
>>>> + * is ballooned out
>>>> + */
>>>> pages = ram_save_host_page(ms, f, &pss,
>>>> last_stage, bytes_transferred,
>>>> dirty_ram_abs);
>>>> @@ -1959,6 +1968,7 @@ static int ram_save_setup(QEMUFile *f, void *opaque)
>>>>
>>>> rcu_read_unlock();
>>>>
>>>> + qemu_balloon_bitmap_setup();
>>>> ram_control_before_iterate(f, RAM_CONTROL_SETUP);
>>>> ram_control_after_iterate(f, RAM_CONTROL_SETUP);
>>>>
>>>> @@ -1984,6 +1994,9 @@ static int ram_save_iterate(QEMUFile *f, void
>>>> *opaque)
>>>>
>>>> ram_control_before_iterate(f, RAM_CONTROL_ROUND);
>>>>
>>>> + qemu_put_be64(f, RAM_SAVE_FLAG_BALLOON);
>>>> + qemu_balloon_bitmap_save(f);
>>>> +
>>>> t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
>>>> i = 0;
>>>> while ((ret = qemu_file_rate_limit(f)) == 0) {
>>>> @@ -2493,6 +2506,10 @@ static int ram_load(QEMUFile *f, void *opaque, int
>>>> version_id)
>>>> }
>>>> break;
>>>>
>>>> + case RAM_SAVE_FLAG_BALLOON:
>>>> + qemu_balloon_bitmap_load(f);
>>>> + break;
>>>> +
>>>> case RAM_SAVE_FLAG_COMPRESS:
>>>> ch = qemu_get_byte(f);
>>>> ram_handle_compressed(host, ch, TARGET_PAGE_SIZE);
>>>> diff --git a/qapi-schema.json b/qapi-schema.json
>>>> index 7f8d799..38163ca 100644
>>>> --- a/qapi-schema.json
>>>> +++ b/qapi-schema.json
>>>> @@ -544,11 +544,14 @@
>>>> # been migrated, pulling the remaining pages along as needed.
>>>> NOTE: If
>>>> # the migration fails during postcopy the VM will fail. (since
>>>> 2.6)
>>>> #
>>>> +# @skip-balloon: Skip scanning ram pages released by virtio-balloon
>>>> driver.
>>>> +# (since 2.7)
>>>> +#
>>>> # Since: 1.2
>>>> ##
>>>> { 'enum': 'MigrationCapability',
>>>> 'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
>>>> - 'compress', 'events', 'postcopy-ram'] }
>>>> + 'compress', 'events', 'postcopy-ram', 'skip-balloon'] }
>>>>
>>>> ##
>>>> # @MigrationCapabilityStatus
>>>> --
>>>> 1.8.3.1