Re: [PATCH v3 21/23] multifd: Support for zero pages transmission

[Dr. David Alan Gilbert]

* Juan Quintela (quintela@redhat.com) wrote:
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> > * Juan Quintela (quintela@redhat.com) wrote:
> >> "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> >> > * Juan Quintela (quintela@redhat.com) wrote:
> >> >> This patch adds counters and similar.  Logic will be added on the
> >> >> following patch.
> >> >> 
> >> >> Signed-off-by: Juan Quintela <quintela@redhat.com>
> >> >> ---
> >> >>  migration/multifd.h    | 13 ++++++++++++-
> >> >>  migration/multifd.c    | 22 +++++++++++++++++++---
> >> >>  migration/trace-events |  2 +-
> >> >>  3 files changed, 32 insertions(+), 5 deletions(-)
> >> >> 
> >> >> diff --git a/migration/multifd.h b/migration/multifd.h
> >> >> index 39e55d7f05..973315b545 100644
> >> >> --- a/migration/multifd.h
> >> >> +++ b/migration/multifd.h
> >> >> @@ -49,7 +49,10 @@ typedef struct {
> >> >>      /* size of the next packet that contains pages */
> >> >>      uint32_t next_packet_size;
> >> >>      uint64_t packet_num;
> >> >> -    uint64_t unused[4];    /* Reserved for future use */
> >> >> +    /* zero pages */
> >> >> +    uint32_t zero_pages;
> >> >
> >> > Had you considered just adding a flag, MULTIFD_FLAG_ZERO to the packet?
> >> 
> >> I *have* to also add the flag.
> >
> > I meant can't you add a flag to say that this whole packet is zero pages
> > and then you only need one counter.
> 
> No, in general packets are going to transmit *both*, zero pages and
> normal pages.  It depends on the content that one receives.

OK, I'd wondered if it was just easier to send two packets; but fine.

Dave

> Later, Juan.
> 
> > Dave
> >
> >> I was waiting for 7.0 to get out, because I still have to do the
> >> compatibility bits.  Otherwise you can't migrate to an old multifd version.
> >> 
> >> >
> >> >> +    uint32_t unused32[1];    /* Reserved for future use */
> >> >> +    uint64_t unused64[3];    /* Reserved for future use */
> >> >>      char ramblock[256];
> >> >>      uint64_t offset[];
> >> >>  } __attribute__((packed)) MultiFDPacket_t;
> >> >> @@ -117,6 +120,10 @@ typedef struct {
> >> >>      ram_addr_t *normal;
> >> >>      /* num of non zero pages */
> >> >>      uint32_t normal_num;
> >> >> +    /* Pages that are  zero */
> >> >> +    ram_addr_t *zero;
> >> >> +    /* num of zero pages */
> >> >> +    uint32_t zero_num;
> >> >>      /* used for compression methods */
> >> >>      void *data;
> >> >>  }  MultiFDSendParams;
> >> >> @@ -162,6 +169,10 @@ typedef struct {
> >> >>      ram_addr_t *normal;
> >> >>      /* num of non zero pages */
> >> >>      uint32_t normal_num;
> >> >> +    /* Pages that are  zero */
> >> >> +    ram_addr_t *zero;
> >> >> +    /* num of zero pages */
> >> >> +    uint32_t zero_num;
> >> >>      /* used for de-compression methods */
> >> >>      void *data;
> >> >>  } MultiFDRecvParams;
> >> >> diff --git a/migration/multifd.c b/migration/multifd.c
> >> >> index d1ab823f98..2e4dffd6c6 100644
> >> >> --- a/migration/multifd.c
> >> >> +++ b/migration/multifd.c
> >> >> @@ -265,6 +265,7 @@ static void 
> >> >> multifd_send_fill_packet(MultiFDSendParams *p)
> >> >>      packet->normal_pages = cpu_to_be32(p->normal_num);
> >> >>      packet->next_packet_size = cpu_to_be32(p->next_packet_size);
> >> >>      packet->packet_num = cpu_to_be64(p->packet_num);
> >> >> +    packet->zero_pages = cpu_to_be32(p->zero_num);
> >> >>  
> >> >>      if (p->pages->block) {
> >> >>          strncpy(packet->ramblock, p->pages->block->idstr, 256);
> >> >> @@ -327,7 +328,15 @@ static int 
> >> >> multifd_recv_unfill_packet(MultiFDRecvParams *p, Error **errp)
> >> >>      p->next_packet_size = be32_to_cpu(packet->next_packet_size);
> >> >>      p->packet_num = be64_to_cpu(packet->packet_num);
> >> >>  
> >> >> -    if (p->normal_num == 0) {
> >> >> +    p->zero_num = be32_to_cpu(packet->zero_pages);
> >> >> +    if (p->zero_num > packet->pages_alloc - p->normal_num) {
> >> >> +        error_setg(errp, "multifd: received packet "
> >> >> +                   "with %d zero pages and expected maximum pages are 
> >> >> %d",
> >> >> +                   p->normal_num, packet->pages_alloc - p->zero_num) ;
> >> >
> >> > should that be p->zero_num, packet->pages_alloc - p->normal_num ?
> >> > (and be %u)
> >> 
> >> Copy and paste error.  You are right on both cases.
> >> 
> >> Thanks.
> >> 
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK