[PATCH 00/11] migration: Make multifd use only one write on the send path

[Juan Quintela]

Hi

Right now, multifd does a write() for the header and a writev() for
each group of pages.  Simplify it so we send the header as another
member of the IOV.

Once there, I got several simplifications:
* is_zero_range() was used only once, just use its body.
* same with is_zero_page().
* Be consintent and use offset insed the ramblock everywhere.
* Now that we have the offsets of the ramblock, we can drop the iov.
* Now that nothing uses iov's except NOCOMP method, move the iovs
  from pages to methods.
* Now we can use iov's with a single field for zlib/zstd.
* send_write() method is the same in all the implementaitons, so use
  it directly.
* Now, we can use a single writev() to write everything.

ToDo: Move zero page detection to the multifd thrteads.

With RAM in the Terabytes size, the detection of the zero page takes
too much time on the main thread.

Last patch on the series removes the detection of zero pages in the
main thread for multifd.  In the next series post, I will add how to
detect the zero pages and send them on multifd channels.

Please review.

Later, Juan.

Juan Quintela (11):
  migration: Remove is_zero_range()
  dump: Remove is_zero_page()
  multifd: Fill offset and block for reception
  multifd: Make zstd compression method not use iovs
  multifd: Make zlib compression method not use iovs
  migration: Move iov from pages to params
  multifd: Make zlib use iov's
  multifd: Make zstd use iov's
  multifd: Remove send_write() method
  multifd: Use a single writev on the send side
  migration: Use multifd before we check for the zero page

 migration/multifd.h      | 10 ++++---
 dump/dump.c              | 10 +------
 migration/multifd-zlib.c | 40 ++++++++------------------
 migration/multifd-zstd.c | 41 ++++++++------------------
 migration/multifd.c      | 62 ++++++++++++++++++----------------------
 migration/ram.c          | 31 +++++++++-----------
 6 files changed, 72 insertions(+), 122 deletions(-)

-- 
2.33.1