Hi Keqian,
> -----Original Message-----
> From: zhukeqian
> Sent: Monday, June 15, 2020 11:19 AM
> To: qemu-devel@nongnu.org; qemu-...@nongnu.org; Paolo Bonzini
> <pbonz...@redhat.com>; Zhoujian (jay) <jianjay.z...@huawei.com>
> Cc: Juan Quintela <quint...@redhat.com>; Chao Fan <fanc.f...@cn.fujitsu.com>;
> Wanghaibin (D) <wanghaibin.w...@huawei.com>
> Subject: Re: [PATCH] migration: Count new_dirty instead of real_dirty
>
> Hi Paolo and Jian Zhou,
>
> Do you have any suggestion on this patch?
>
> Thanks,
> Keqian
>
> On 2020/6/1 12:02, Keqian Zhu wrote:
> > DIRTY_LOG_INITIALLY_ALL_SET feature is on the queue. This fixs the
s/fixs/fixes
> > dirty rate calculation for this feature. After introducing this
> > feature, real_dirty_pages is equal to total memory size at begining.
> > This causing wrong dirty rate and false positive throttling.
I think it should be tested whether DIRTY_LOG_INITIALLY_ALL_SET is enabled
in ram_init_bitmaps(maybe?) in order to be compatible with the old path.
Thanks,
Jay Zhou
> >
> > BTW, real dirty rate is not suitable and not very accurate.
> >
> > 1. For not suitable: We mainly concern on the relationship between
> > dirty rate and network bandwidth. Net increasement of dirty pages
> > makes more sense.
> > 2. For not very accurate: With manual dirty log clear, some dirty pages
> > will be cleared during each peroid, our "real dirty rate" is less
> > than real "real dirty rate".
> >
> > Signed-off-by: Keqian Zhu <zhukeqi...@huawei.com>
> > ---
> > include/exec/ram_addr.h | 5 ++---
> > 1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h index
> > 5e59a3d8d7..af9677e291 100644
> > --- a/include/exec/ram_addr.h
> > +++ b/include/exec/ram_addr.h
> > @@ -443,7 +443,7 @@ static inline
> > uint64_t cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb,
> > ram_addr_t start,
> > ram_addr_t length,
> > - uint64_t
> *real_dirty_pages)
> > + uint64_t
> > + *accu_dirty_pages)
> > {
> > ram_addr_t addr;
> > unsigned long word = BIT_WORD((start + rb->offset) >>
> > TARGET_PAGE_BITS); @@ -469,7 +469,6 @@ uint64_t
> cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb,
> > if (src[idx][offset]) {
> > unsigned long bits = atomic_xchg(&src[idx][offset], 0);
> > unsigned long new_dirty;
> > - *real_dirty_pages += ctpopl(bits);
> > new_dirty = ~dest[k];
> > dest[k] |= bits;
> > new_dirty &= bits;
> > @@ -502,7 +501,6 @@ uint64_t
> cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb,
> > start + addr + offset,
> > TARGET_PAGE_SIZE,
> > DIRTY_MEMORY_MIGRATION)) {
> > - *real_dirty_pages += 1;
> > long k = (start + addr) >> TARGET_PAGE_BITS;
> > if (!test_and_set_bit(k, dest)) {
> > num_dirty++;
> > @@ -511,6 +509,7 @@ uint64_t
> cpu_physical_memory_sync_dirty_bitmap(RAMBlock *rb,
> > }
> > }
> >
> > + *accu_dirty_pages += num_dirty;
> > return num_dirty;
> > }
> > #endif
> >
