On Tue, Mar 28, 2017 at 08:43:37PM +0200, Juan Quintela wrote:
> Peter Xu <pet...@redhat.com> wrote:
> > On Thu, Mar 23, 2017 at 09:45:04PM +0100, Juan Quintela wrote:
> >> Once there rename it to its actual meaning, zero_pages.
> >>
> >> Signed-off-by: Juan Quintela <quint...@redhat.com>
> >> Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> >
> > Reviewed-by: Peter Xu <pet...@redhat.com>
> >
> > Will post a question below though (not directly related to this patch
> > but context-wide)...
> >> {
> >> int pages = -1;
> >>
> >> if (is_zero_range(p, TARGET_PAGE_SIZE)) {
> >> - acct_info.dup_pages++;
> >> + rs->zero_pages++;
> >> *bytes_transferred += save_page_header(f, block,
> >> offset |
> >> RAM_SAVE_FLAG_COMPRESS);
> >> qemu_put_byte(f, 0);
> >> @@ -822,11 +826,11 @@ static int ram_save_page(RAMState *rs,
> >> MigrationState *ms, QEMUFile *f,
> >> if (bytes_xmit > 0) {
> >> acct_info.norm_pages++;
> >> } else if (bytes_xmit == 0) {
> >> - acct_info.dup_pages++;
> >> + rs->zero_pages++;
> >
> > This code path looks suspicous... since iiuc currently it should only
> > be triggered by RDMA case, and I believe here qemu_rdma_save_page()
> > should have met something wrong (so that it didn't return with
> > RAM_SAVE_CONTROL_DELAYED). Then is it correct we do increase zero page
> > counting unconditionally here? (hmm, the default bytes_xmit is zero as
> > well...)
>
> My head hurts at this point.
Sorry about that! :(
> ok. bytse_xmit can only be zero if we called qemu_rdma_save_page() with
> size=0 or there has been an RDMA error. We ver call the function with
> size = 0. And if there is one error, we are in very bady shape already.
>
> > Another thing is that I see when RDMA is enabled we are updating
> > accounting info with acct_update_position(), while we updated it here
> > as well. Is this an issue of duplicated accounting?
>
> I think stats and rdma are not right. I have to check more that.
Sorry to have led the discussion too far away from the topic. I guess
it'll be perfectly okay to just mark this as TODO item, and we can
just move on with current series (and I believe you have further
patches after this big one :).
Out of curiosity - to what extent are people using migration with
RDMA? Should that be "very rare"? Thanks,
-- peterx
