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Re: [Qemu-devel] [PATCH v4 4/4] migration: use the free page hint featur
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH v4 4/4] migration: use the free page hint feature from balloon |
Date: |
Wed, 14 Mar 2018 04:51:05 +0200 |
On Wed, Mar 14, 2018 at 10:41:36AM +0800, Wei Wang wrote:
> On 03/14/2018 12:35 AM, Michael S. Tsirkin wrote:
> > On Wed, Mar 07, 2018 at 08:34:25PM +0800, Wei Wang wrote:
> > > Start the free page optimization after the migration bitmap is
> > > synchronized. This can't be used in the stop© phase since the guest
> > > is paused. Make sure the guest reporting has stopped before
> > > synchronizing the migration dirty bitmap. Currently, the optimization is
> > > added to precopy only.
> > >
> > > Signed-off-by: Wei Wang <address@hidden>
> > > CC: Dr. David Alan Gilbert <address@hidden>
> > > CC: Juan Quintela <address@hidden>
> > > CC: Michael S. Tsirkin <address@hidden>
> > > ---
> > > migration/ram.c | 19 ++++++++++++++++++-
> > > 1 file changed, 18 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/migration/ram.c b/migration/ram.c
> > > index e172798..7b4c9b1 100644
> > > --- a/migration/ram.c
> > > +++ b/migration/ram.c
> > > @@ -51,6 +51,8 @@
> > > #include "qemu/rcu_queue.h"
> > > #include "migration/colo.h"
> > > #include "migration/block.h"
> > > +#include "sysemu/balloon.h"
> > > +#include "sysemu/sysemu.h"
> > > /***********************************************************/
> > > /* ram save/restore */
> > > @@ -208,6 +210,8 @@ struct RAMState {
> > > uint32_t last_version;
> > > /* We are in the first round */
> > > bool ram_bulk_stage;
> > > + /* The free pages optimization feature is supported */
> > > + bool free_page_support;
> > > /* How many times we have dirty too many pages */
> > > int dirty_rate_high_cnt;
> > > /* these variables are used for bitmap sync */
> > > @@ -775,7 +779,7 @@ unsigned long migration_bitmap_find_dirty(RAMState
> > > *rs, RAMBlock *rb,
> > > unsigned long *bitmap = rb->bmap;
> > > unsigned long next;
> > > - if (rs->ram_bulk_stage && start > 0) {
> > > + if (rs->ram_bulk_stage && start > 0 && !rs->free_page_support) {
> > > next = start + 1;
> > > } else {
> > > next = find_next_bit(bitmap, size, start);
> > > @@ -833,6 +837,10 @@ static void migration_bitmap_sync(RAMState *rs)
> > > int64_t end_time;
> > > uint64_t bytes_xfer_now;
> > > + if (rs->free_page_support) {
> > > + balloon_free_page_stop();
> > > + }
> > > +
> > > ram_counters.dirty_sync_count++;
> > > if (!rs->time_last_bitmap_sync) {
> > > @@ -899,6 +907,10 @@ static void migration_bitmap_sync(RAMState *rs)
> > > if (migrate_use_events()) {
> > > qapi_event_send_migration_pass(ram_counters.dirty_sync_count,
> > > NULL);
> > > }
> > > +
> > > + if (rs->free_page_support && runstate_is_running()) {
> > > + balloon_free_page_start();
> > > + }
> > > }
> > I think some of these conditions should go into
> > balloon_free_page_start/stop.
> >
> > Checking runstate is generally problematic unless you
> > also handle run state change notifiers as it can
> > be manipulated from QMP.
>
> How about moving the check of runstate to
> virtio_balloon_poll_free_page_hints:
>
> while (dev->free_page_report_status < FREE_PAGE_REPORT_S_STOP &&
> runstate_is_running()) {
> ...
> }
Hard to tell on the outset. E.g. why is just stop affected? Pls add
comments explaining what happens if VM is not running when start or stop
is called.
> In this case, I think we won't need a notifier - if the run state is changed
> by qmp, the optimization thread will just exist.
But you need to wake it up and notify the guest presumably?
>
> > > /**
> > > @@ -1656,6 +1668,8 @@ static void ram_state_reset(RAMState *rs)
> > > rs->last_page = 0;
> > > rs->last_version = ram_list.version;
> > > rs->ram_bulk_stage = true;
> > > + rs->free_page_support = balloon_free_page_support() &
> > > + !migration_in_postcopy();
> > Probably &&?
> >
>
> OK, will use &&. (Both work well here actually, since all of the values here
> are boolean)
>
>
> Best,
> Wei
- Re: [Qemu-devel] [PATCH v4 2/4] migration: API to clear bits of guest free pages from the dirty bitmap, (continued)
- Re: [Qemu-devel] [PATCH v4 2/4] migration: API to clear bits of guest free pages from the dirty bitmap, Michael S. Tsirkin, 2018/03/14
- Re: [Qemu-devel] [PATCH v4 2/4] migration: API to clear bits of guest free pages from the dirty bitmap, Wei Wang, 2018/03/15
- Re: [Qemu-devel] [PATCH v4 2/4] migration: API to clear bits of guest free pages from the dirty bitmap, Wei Wang, 2018/03/15
- Re: [Qemu-devel] [PATCH v4 2/4] migration: API to clear bits of guest free pages from the dirty bitmap, Michael S. Tsirkin, 2018/03/15
- Re: [Qemu-devel] [PATCH v4 2/4] migration: API to clear bits of guest free pages from the dirty bitmap, Wei Wang, 2018/03/16
[Qemu-devel] [PATCH v4 1/4] bitmap: bitmap_count_one_with_offset, Wei Wang, 2018/03/07
[Qemu-devel] [PATCH v4 4/4] migration: use the free page hint feature from balloon, Wei Wang, 2018/03/07
Re: [Qemu-devel] [PATCH v4 4/4] migration: use the free page hint feature from balloon, Dr. David Alan Gilbert, 2018/03/14
[Qemu-devel] [PATCH v4 3/4] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT, Wei Wang, 2018/03/07