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Re: [PATCH v3 23/23] migration: Use multifd before we check for the zero
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH v3 23/23] migration: Use multifd before we check for the zero page |
Date: |
Thu, 2 Dec 2021 17:49:09 +0000 |
User-agent: |
Mutt/2.1.3 (2021-09-10) |
* Juan Quintela (quintela@redhat.com) wrote:
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> > * Juan Quintela (quintela@redhat.com) wrote:
> >> So we use multifd to transmit zero pages.
> >>
> >> Signed-off-by: Juan Quintela <quintela@redhat.com>
> >> ---
> >> migration/ram.c | 22 +++++++++++-----------
> >> 1 file changed, 11 insertions(+), 11 deletions(-)
> >>
> >> diff --git a/migration/ram.c b/migration/ram.c
> >> index 57efa67f20..3ae094f653 100644
> >> --- a/migration/ram.c
> >> +++ b/migration/ram.c
> >> @@ -2138,6 +2138,17 @@ static int ram_save_target_page(RAMState *rs,
> >> PageSearchStatus *pss,
> >> ram_addr_t offset = ((ram_addr_t)pss->page) << TARGET_PAGE_BITS;
> >> int res;
> >>
> >> + /*
> >> + * Do not use multifd for:
> >> + * 1. Compression as the first page in the new block should be posted
> >> out
> >> + * before sending the compressed page
> >> + * 2. In postcopy as one whole host page should be placed
> >> + */
> >> + if (!save_page_use_compression(rs) && migrate_use_multifd()
> >> + && !migration_in_postcopy()) {
> >> + return ram_save_multifd_page(rs, block, offset);
> >> + }
> >> +
> >> if (control_save_page(rs, block, offset, &res)) {
> >> return res;
> >> }
> >
> > Although I don't think it currently matters, I think that should be
> > after the control_save_page.
>
> This needs to be improved to be compatible with old versions.
>
> But .... if we don't care about RDMA, why do we care about
> control_save_page()?
That's why I said I don't think it currently matters; but the patch
seemed a little odd since it changed this order which isn't what
it said.
Dave
> Later, Juan.
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK