On Tuesday, July 13, 2021 11:59 PM, Peter Xu wrote:
> On Tue, Jul 13, 2021 at 08:40:21AM +, Wang, Wei W wrote:
>
> Didn't get a chance to document it as it's in a pull now; but as long as
> you're okay
> with no-per-page lock (which I still don't agree with), I can follow this up.
>
> Are be
On Tuesday, July 13, 2021 6:22 PM, David Hildenbrand wrote:
> Can you send an official patch for the free page hinting clean_bmap handling I
> reported?
>
> I can then give both tests in combination a quick test (before/after this
> patch
> here).
>
Yes, I'll send, thanks!
Best,
Wei
On Tue, Jul 13, 2021 at 08:40:21AM +, Wang, Wei W wrote:
> On Thursday, July 1, 2021 4:08 AM, Peter Xu wrote:
> > Taking the mutex every time for each dirty bit to clear is too slow,
> > especially we'll
> > take/release even if the dirty bit is cleared. So far it's only used to
> > sync wit
On 13.07.21 10:40, Wang, Wei W wrote:
On Thursday, July 1, 2021 4:08 AM, Peter Xu wrote:
Taking the mutex every time for each dirty bit to clear is too slow, especially
we'll
take/release even if the dirty bit is cleared. So far it's only used to sync
with
special cases with qemu_guest_free_p
On Thursday, July 1, 2021 4:08 AM, Peter Xu wrote:
> Taking the mutex every time for each dirty bit to clear is too slow,
> especially we'll
> take/release even if the dirty bit is cleared. So far it's only used to sync
> with
> special cases with qemu_guest_free_page_hint() against migration th
On Friday, July 9, 2021 10:48 PM, Peter Xu wrote:
> On Fri, Jul 09, 2021 at 08:58:08AM +, Wang, Wei W wrote:
> > On Friday, July 9, 2021 2:31 AM, Peter Xu wrote:
> > > > > Yes I think this is the place I didn't make myself clear. It's
> > > > > not about sleeping, it's about the cmpxchg being
On Fri, Jul 09, 2021 at 08:58:08AM +, Wang, Wei W wrote:
> On Friday, July 9, 2021 2:31 AM, Peter Xu wrote:
> > > > Yes I think this is the place I didn't make myself clear. It's not
> > > > about sleeping, it's about the cmpxchg being expensive already when the
> > > > vm
> > is huge.
> > >
On Friday, July 9, 2021 2:31 AM, Peter Xu wrote:
> > > Yes I think this is the place I didn't make myself clear. It's not
> > > about sleeping, it's about the cmpxchg being expensive already when the vm
> is huge.
> >
> > OK.
> > How did you root cause that it's caused by cmpxchg, instead of lock
On Thu, Jul 08, 2021 at 02:55:23AM +, Wang, Wei W wrote:
> On Thursday, July 8, 2021 12:55 AM, Peter Xu wrote:
> > On Wed, Jul 07, 2021 at 08:34:50AM +, Wang, Wei W wrote:
> > > On Wednesday, July 7, 2021 1:47 AM, Peter Xu wrote:
> > > > On Sat, Jul 03, 2021 at 02:53:27AM +, Wang, Wei W
On Thu, Jul 08, 2021 at 02:49:51AM +, Wang, Wei W wrote:
> On Thursday, July 8, 2021 12:44 AM, Peter Xu wrote:
> > > > Not to mention the hard migration issues are mostly with non-idle
> > > > guest, in that case having the balloon in the guest will be
> > > > disastrous from this pov since it'
On Thursday, July 8, 2021 12:55 AM, Peter Xu wrote:
> On Wed, Jul 07, 2021 at 08:34:50AM +, Wang, Wei W wrote:
> > On Wednesday, July 7, 2021 1:47 AM, Peter Xu wrote:
> > > On Sat, Jul 03, 2021 at 02:53:27AM +, Wang, Wei W wrote:
> > > > + do {
> > > > +page_to_clear = sta
On Thursday, July 8, 2021 12:44 AM, Peter Xu wrote:
> > > Not to mention the hard migration issues are mostly with non-idle
> > > guest, in that case having the balloon in the guest will be
> > > disastrous from this pov since it'll start to take mutex for each
> > > page, while balloon would hardl
On Wed, Jul 07, 2021 at 11:25:50PM +, Wang, Wei W wrote:
> On Thursday, July 8, 2021 12:45 AM, Peter Xu wrote:
> > On Wed, Jul 07, 2021 at 12:45:32PM +, Wang, Wei W wrote:
> > > Btw, what would you think if we change mutex to QemuSpin? It will also
> > > reduce
> > the overhead, I think.
>
On Thursday, July 8, 2021 12:45 AM, Peter Xu wrote:
> On Wed, Jul 07, 2021 at 12:45:32PM +, Wang, Wei W wrote:
> > Btw, what would you think if we change mutex to QemuSpin? It will also
> > reduce
> the overhead, I think.
>
> As I replied at the other place, the bottleneck we encountered is t
On Wed, Jul 07, 2021 at 08:34:50AM +, Wang, Wei W wrote:
> On Wednesday, July 7, 2021 1:47 AM, Peter Xu wrote:
> > On Sat, Jul 03, 2021 at 02:53:27AM +, Wang, Wei W wrote:
> > > + do {
> > > +page_to_clear = start + (i++ << block->clear_bmap_shift);
> >
> > Why "i" needs
On Wed, Jul 07, 2021 at 12:45:32PM +, Wang, Wei W wrote:
> Btw, what would you think if we change mutex to QemuSpin? It will also reduce
> the overhead, I think.
As I replied at the other place, the bottleneck we encountered is the lock
taking not sleeping, so I'm afraid spinlock will have th
On Wed, Jul 07, 2021 at 08:33:21AM +, Wang, Wei W wrote:
> On Wednesday, July 7, 2021 2:00 AM, Peter Xu wrote:
> > On Fri, Jul 02, 2021 at 02:29:41AM +, Wang, Wei W wrote:
> > > With that, if free page opt is off, the mutex is skipped, isn't it?
> >
> > Yes, but when free page is on, it'll
On Wednesday, July 7, 2021 1:40 AM, Peter Xu wrote:
> On Tue, Jul 06, 2021 at 12:05:49PM +0200, David Hildenbrand wrote:
> > On 06.07.21 11:41, Wang, Wei W wrote:
> > > On Monday, July 5, 2021 9:42 PM, David Hildenbrand wrote:
> > > > On 03.07.21 04:53, Wang, Wei W wrote:
> > > > > On Friday, July
On Wednesday, July 7, 2021 2:00 AM, Peter Xu wrote:
> On Fri, Jul 02, 2021 at 02:29:41AM +, Wang, Wei W wrote:
> > With that, if free page opt is off, the mutex is skipped, isn't it?
>
> Yes, but when free page is on, it'll check once per page. As I mentioned I
> still
> don't think it's the
On Wednesday, July 7, 2021 1:47 AM, Peter Xu wrote:
> On Sat, Jul 03, 2021 at 02:53:27AM +, Wang, Wei W wrote:
> > + do {
> > +page_to_clear = start + (i++ << block->clear_bmap_shift);
>
> Why "i" needs to be shifted?
Just move to the next clear chunk, no?
For example, (1 <<
On Sun, Jul 04, 2021 at 04:14:57PM +0200, Lukas Straub wrote:
> On Sat, 3 Jul 2021 18:31:15 +0200
> Lukas Straub wrote:
>
> > On Wed, 30 Jun 2021 16:08:05 -0400
> > Peter Xu wrote:
> >
> > > Taking the mutex every time for each dirty bit to clear is too slow,
> > > especially
> > > we'll take/
On Fri, Jul 02, 2021 at 02:29:41AM +, Wang, Wei W wrote:
> On Thursday, July 1, 2021 8:51 PM, Peter Xu wrote:
> > On Thu, Jul 01, 2021 at 04:42:38AM +, Wang, Wei W wrote:
> > > On Thursday, July 1, 2021 4:08 AM, Peter Xu wrote:
> > > > Taking the mutex every time for each dirty bit to clear
On Sat, Jul 03, 2021 at 02:53:27AM +, Wang, Wei W wrote:
> On Friday, July 2, 2021 3:07 PM, David Hildenbrand wrote:
> > On 02.07.21 04:48, Wang, Wei W wrote:
> > > On Thursday, July 1, 2021 10:22 PM, David Hildenbrand wrote:
> > >> On 01.07.21 14:51, Peter Xu wrote:
> >
> > I think that clear
On Tue, Jul 06, 2021 at 12:05:49PM +0200, David Hildenbrand wrote:
> On 06.07.21 11:41, Wang, Wei W wrote:
> > On Monday, July 5, 2021 9:42 PM, David Hildenbrand wrote:
> > > On 03.07.21 04:53, Wang, Wei W wrote:
> > > > On Friday, July 2, 2021 3:07 PM, David Hildenbrand wrote:
> > > > > On 02.07.2
On 06.07.21 11:41, Wang, Wei W wrote:
On Monday, July 5, 2021 9:42 PM, David Hildenbrand wrote:
On 03.07.21 04:53, Wang, Wei W wrote:
On Friday, July 2, 2021 3:07 PM, David Hildenbrand wrote:
On 02.07.21 04:48, Wang, Wei W wrote:
On Thursday, July 1, 2021 10:22 PM, David Hildenbrand wrote:
O
On Monday, July 5, 2021 9:42 PM, David Hildenbrand wrote:
> On 03.07.21 04:53, Wang, Wei W wrote:
> > On Friday, July 2, 2021 3:07 PM, David Hildenbrand wrote:
> >> On 02.07.21 04:48, Wang, Wei W wrote:
> >>> On Thursday, July 1, 2021 10:22 PM, David Hildenbrand wrote:
> On 01.07.21 14:51, Pet
On 03.07.21 04:53, Wang, Wei W wrote:
On Friday, July 2, 2021 3:07 PM, David Hildenbrand wrote:
On 02.07.21 04:48, Wang, Wei W wrote:
On Thursday, July 1, 2021 10:22 PM, David Hildenbrand wrote:
On 01.07.21 14:51, Peter Xu wrote:
I think that clearly shows the issue.
My theory I did not ver
On Sat, 3 Jul 2021 18:31:15 +0200
Lukas Straub wrote:
> On Wed, 30 Jun 2021 16:08:05 -0400
> Peter Xu wrote:
>
> > Taking the mutex every time for each dirty bit to clear is too slow,
> > especially
> > we'll take/release even if the dirty bit is cleared. So far it's only used
> > to
> > syn
On Wed, 30 Jun 2021 16:08:05 -0400
Peter Xu wrote:
> Taking the mutex every time for each dirty bit to clear is too slow,
> especially
> we'll take/release even if the dirty bit is cleared. So far it's only used to
> sync with special cases with qemu_guest_free_page_hint() against migration
> t
On Friday, July 2, 2021 3:07 PM, David Hildenbrand wrote:
> On 02.07.21 04:48, Wang, Wei W wrote:
> > On Thursday, July 1, 2021 10:22 PM, David Hildenbrand wrote:
> >> On 01.07.21 14:51, Peter Xu wrote:
>
> I think that clearly shows the issue.
>
> My theory I did not verify yet: Assume we have 1
On 02.07.21 04:48, Wang, Wei W wrote:
On Thursday, July 1, 2021 10:22 PM, David Hildenbrand wrote:
On 01.07.21 14:51, Peter Xu wrote:
Spoiler alert: the introduction of clean bitmaps partially broke free page
hinting
already (as clearing happens deferred -- and might never happen if we don't
mi
On Thursday, July 1, 2021 10:22 PM, David Hildenbrand wrote:
> On 01.07.21 14:51, Peter Xu wrote:
> Spoiler alert: the introduction of clean bitmaps partially broke free page
> hinting
> already (as clearing happens deferred -- and might never happen if we don't
> migrate *any* page within a clean
On Thursday, July 1, 2021 8:51 PM, Peter Xu wrote:
> On Thu, Jul 01, 2021 at 04:42:38AM +, Wang, Wei W wrote:
> > On Thursday, July 1, 2021 4:08 AM, Peter Xu wrote:
> > > Taking the mutex every time for each dirty bit to clear is too slow,
> > > especially we'll take/release even if the dirty b
On 01.07.21 14:51, Peter Xu wrote:
On Thu, Jul 01, 2021 at 04:42:38AM +, Wang, Wei W wrote:
On Thursday, July 1, 2021 4:08 AM, Peter Xu wrote:
Taking the mutex every time for each dirty bit to clear is too slow, especially
we'll
take/release even if the dirty bit is cleared. So far it's o
On Thu, Jul 01, 2021 at 04:42:38AM +, Wang, Wei W wrote:
> On Thursday, July 1, 2021 4:08 AM, Peter Xu wrote:
> > Taking the mutex every time for each dirty bit to clear is too slow,
> > especially we'll
> > take/release even if the dirty bit is cleared. So far it's only used to
> > sync wit
On Thursday, July 1, 2021 4:08 AM, Peter Xu wrote:
> Taking the mutex every time for each dirty bit to clear is too slow,
> especially we'll
> take/release even if the dirty bit is cleared. So far it's only used to sync
> with
> special cases with qemu_guest_free_page_hint() against migration th
Taking the mutex every time for each dirty bit to clear is too slow, especially
we'll take/release even if the dirty bit is cleared. So far it's only used to
sync with special cases with qemu_guest_free_page_hint() against migration
thread, nothing really that serious yet. Let's move the lock to
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