[Qemu-devel] [PATCH 0/3] memory: an optimization

[Gonglei]

Perf top tells me qemu_get_ram_ptr consume too much cpu cycles.
> 22.56%  qemu-kvm                 [.] address_space_translate
>  13.29%  qemu-kvm                 [.] qemu_get_ram_ptr
>   4.71%  qemu-kvm                 [.] phys_page_find
>   4.43%  qemu-kvm                 [.] address_space_translate_internal
>   3.47%  libpthread-2.19.so       [.] __pthread_mutex_unlock_usercnt
>   3.08%  qemu-kvm                 [.] qemu_ram_addr_from_host
>   2.62%  qemu-kvm                 [.] address_space_map
>   2.61%  libc-2.19.so             [.] _int_malloc
>   2.58%  libc-2.19.so             [.] _int_free
>   2.38%  libc-2.19.so             [.] malloc
>   2.06%  libpthread-2.19.so       [.] pthread_mutex_lock
>   1.68%  libc-2.19.so             [.] malloc_consolidate
>   1.35%  libc-2.19.so             [.] __memcpy_sse2_unaligned
>   1.23%  qemu-kvm                 [.] lduw_le_phys
>   1.18%  qemu-kvm                 [.] find_next_zero_bit
>   1.02%  qemu-kvm                 [.] object_unref

And Paolo suggested that we can get rid of qemu_get_ram_ptr
by storing the RAMBlock pointer into the memory region,
instead of the ram_addr_t value. And after appling this change,
I got much better performance indeed.

BTW, PATCH 3 is an occasional find.

Gonglei (3):
  exec: store RAMBlock pointer into memory region
  memory: optimize qemu_get_ram_ptr and qemu_ram_ptr_length
  memory: Remove the superfluous code

 exec.c                | 48 ++++++++++++++++++++++++++++++------------------
 include/exec/memory.h |  7 +++----
 memory.c              |  3 ++-
 3 files changed, 35 insertions(+), 23 deletions(-)

-- 
1.8.5.2