[Qemu-devel] [PATCHv3 0/9] buffer_is_zero / migration optimizations

[Peter Lieven <pl@kamp.de>]

this is v3 of my patch series with various optimizations in
zero buffer checking and migration tweaks.

thanks especially to Eric Blake for reviewing.

v3:
 - remove asserts, inline functions and add a check
   function if buffer_find_nonzero_offset() can be used.
 - use above check function in buffer_is_zero() and
   find_next_bit().
 - use buffer_is_nonzero_offset() directly to find
   zero pages. we know that all requirements are met
   for memory pages.
 - fix C89 violation in buffer_is_zero().
 - avoid derefencing p in ram_save_block() if we already
   know the page is zero.
 - fix initialization of last_offset in reset_ram_globals().
 - avoid skipping pages with offset == 0 in bulk stage in
   migration_bitmap_find_and_reset_dirty().
 - compared to v1 check for zero pages also after bulk
   ram migration as there are guests (e.g. Windows) which
   zero out large amount of memory while running.

v2:
 - fix description, add trivial zero check and add asserts 
   to buffer_find_nonzero_offset.
 - add a constant for the unroll factor of buffer_find_nonzero_offset
 - replace is_dup_page() by buffer_is_zero()
 - added test results to xbzrle patch
 - optimize descriptions

Peter Lieven (9):
  move vector definitions to qemu-common.h
  cutils: add a function to find non-zero content in a buffer
  buffer_is_zero: use vector optimizations if possible
  bitops: use vector algorithm to optimize find_next_bit()
  migration: search for zero instead of dup pages
  migration: add an indicator for bulk state of ram migration
  migration: do not sent zero pages in bulk stage
  migration: do not search dirty pages in bulk stage
  migration: use XBZRLE only after bulk stage

 arch_init.c           |   62 ++++++++++++++++++-------------------------------
 include/qemu-common.h |   27 +++++++++++++++++++++
 util/bitops.c         |   22 +++++++++++++++---
 util/cutils.c         |   55 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 123 insertions(+), 43 deletions(-)

-- 
1.7.9.5