* Bohdan Trach (bohdan.tr...@mailbox.tu-dresden.de) wrote: > > On 11/17/2015 05:05 PM, Dr. David Alan Gilbert wrote: > > Why is the hash needed on the destination; if it's a page which the source > > has decided isn't in a matching page, what does the destination use the > > hash for? > > > > After the migration has finished, the hashes are still stored in RAM > for the next migration, when the current destination becomes the new > migration source. This way there is no need to recompute the checksums > on the next migration -- they are already in RAM. > > >>> I think there's a problem here that given the source is still running > >>> it's CPU and changing > >>> memory; it can be writing to the page at the same time, so the page you > >>> send might not > >>> match the hash you send; we're guaranteed to resend the page again if it > >>> was written > >>> to, but that still doesn't make these two things match; although as I say > >>> above > >>> I'm not sure why SAVE_FLAG_PAGE_HASH exists. > >> > >> This is true. In this case, we will just delete the SAVE_FLAG_PAGE_HASH > >> flag. > > > > But how do you know to delete the SAVE_FLAG_PAGE_HASH flag? > > > > Sorry for not stating this clear enough. We will remove this flag from > the code, and send pages with SAVE_FLAG_PAGE instead. In this case the > destination will compute the hash.
OK, that's fine. Dave > > > -- > > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK > > > > -- > With best regards, > Bohdan Trach -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
