From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57581) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cYaA5-0007kK-U7 for qemu-devel@nongnu.org; Tue, 31 Jan 2017 10:16:03 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cYaA4-0001At-NE for qemu-devel@nongnu.org; Tue, 31 Jan 2017 10:16:01 -0500 Date: Tue, 31 Jan 2017 15:15:48 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20170131151548.GJ2395@work-vm> References: <1479837270-79005-1-git-send-email-vsementsov@virtuozzo.com> <1479837270-79005-4-git-send-email-vsementsov@virtuozzo.com> <87mvegajzv.fsf@emacs.mitica> <7890fa87-faa1-fd99-e8c8-76b51f039ad6@virtuozzo.com> <20170124195334.GF2220@work-vm> <86b7650e-de88-e058-84cc-ce22b91eabff@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86b7650e-de88-e058-84cc-ce22b91eabff@virtuozzo.com> Subject: Re: [Qemu-devel] [PATCH 03/17] migration: split common postcopy out of ram postcopy List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vladimir Sementsov-Ogievskiy Cc: quintela@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, pbonzini@redhat.com, armbru@redhat.com, eblake@redhat.com, famz@redhat.com, stefanha@redhat.com, amit.shah@redhat.com, mreitz@redhat.com, kwolf@redhat.com, peter.maydell@linaro.org, den@openvz.org, jsnow@redhat.com, lirans@il.ibm.com * Vladimir Sementsov-Ogievskiy (vsementsov@virtuozzo.com) wrote: > 24.01.2017 22:53, Dr. David Alan Gilbert wrote: > > * Vladimir Sementsov-Ogievskiy (vsementsov@virtuozzo.com) wrote: > > > 24.01.2017 12:24, Juan Quintela wrote: > > > > Vladimir Sementsov-Ogievskiy wrote: > > > > > Split common postcopy staff from ram postcopy staff. > > > > > > > > > > Signed-off-by: Vladimir Sementsov-Ogievskiy > > > > > --- > > > > > include/migration/migration.h | 1 + > > > > > migration/migration.c | 39 +++++++++++++++++++++++++++------------ > > > > > migration/postcopy-ram.c | 4 +++- > > > > > migration/savevm.c | 31 ++++++++++++++++++++++--------- > > > > > 4 files changed, 53 insertions(+), 22 deletions(-) > > > > > > > > > Hi > > > > > > > > { > > > > > MigrationState *s; > > > > > @@ -1587,9 +1592,11 @@ static int postcopy_start(MigrationState *ms, bool *old_vm_running) > > > > > * need to tell the destination to throw any pages it's already received > > > > > * that are dirty > > > > > */ > > > > > - if (ram_postcopy_send_discard_bitmap(ms)) { > > > > > - error_report("postcopy send discard bitmap failed"); > > > > > - goto fail; > > > > > + if (migrate_postcopy_ram()) { > > > > > + if (ram_postcopy_send_discard_bitmap(ms)) { > > > > > + error_report("postcopy send discard bitmap failed"); > > > > > + goto fail; > > > > > + } > > > > I will have preffered that for the ram commands, to embed the > > > > migrate_postocpy_ram() check inside them, but that is taste, and > > > > everyone has its own O:-) > > > > > > > > > diff --git a/migration/savevm.c b/migration/savevm.c > > > > > index e436cb2..c8a71c8 100644 > > > > > --- a/migration/savevm.c > > > > > +++ b/migration/savevm.c > > > > > @@ -73,7 +73,7 @@ static struct mig_cmd_args { > > > > > [MIG_CMD_INVALID] = { .len = -1, .name = "INVALID" }, > > > > > [MIG_CMD_OPEN_RETURN_PATH] = { .len = 0, .name = "OPEN_RETURN_PATH" }, > > > > > [MIG_CMD_PING] = { .len = sizeof(uint32_t), .name = "PING" }, > > > > > - [MIG_CMD_POSTCOPY_ADVISE] = { .len = 16, .name = "POSTCOPY_ADVISE" }, > > > > > + [MIG_CMD_POSTCOPY_ADVISE] = { .len = -1, .name = "POSTCOPY_ADVISE" }, > > > > > [MIG_CMD_POSTCOPY_LISTEN] = { .len = 0, .name = "POSTCOPY_LISTEN" }, > > > > > [MIG_CMD_POSTCOPY_RUN] = { .len = 0, .name = "POSTCOPY_RUN" }, > > > > > [MIG_CMD_POSTCOPY_RAM_DISCARD] = { > > > > > @@ -827,12 +827,17 @@ int qemu_savevm_send_packaged(QEMUFile *f, const uint8_t *buf, size_t len) > > > > > /* Send prior to any postcopy transfer */ > > > > > void qemu_savevm_send_postcopy_advise(QEMUFile *f) > > > > > { > > > > > - uint64_t tmp[2]; > > > > > - tmp[0] = cpu_to_be64(getpagesize()); > > > > > - tmp[1] = cpu_to_be64(1ul << qemu_target_page_bits()); > > > > > + if (migrate_postcopy_ram()) { > > > > > + uint64_t tmp[2]; > > > > > + tmp[0] = cpu_to_be64(getpagesize()); > > > > > + tmp[1] = cpu_to_be64(1ul << qemu_target_page_bits()); > > > > > - trace_qemu_savevm_send_postcopy_advise(); > > > > > - qemu_savevm_command_send(f, MIG_CMD_POSTCOPY_ADVISE, 16, (uint8_t *)tmp); > > > > > + trace_qemu_savevm_send_postcopy_advise(); > > > > > + qemu_savevm_command_send(f, MIG_CMD_POSTCOPY_ADVISE, > > > > > + 16, (uint8_t *)tmp); > > > > > + } else { > > > > > + qemu_savevm_command_send(f, MIG_CMD_POSTCOPY_ADVISE, 0, NULL); > > > > > + } > > > > > } > > > > > /* Sent prior to starting the destination running in postcopy, discard pages > > > > I haven't yet figured out why you are reusing this command with a > > > > different number of parameters. > > > > For this to pass, I need that Dave comment on this. > > > > > > > > So, > > > > > > > > Reviewed-by: Juan Quintela > > > > > > > > conditioned that Dave agrees with this. > > > These parameters are unrelated if ram postcopy is disabled. So, I should be > > > better to have a possibility of skipping them, then to send unneeded numbers > > > and write separate code to read them from the stream (rewriting > > > loadvm_postcopy_handle_advise to just read these two numbers and do nothing > > > about ram postcopy for this case). > > I think I'd prefer either a new command or keeping these fields (probably all 0 ?) > > my worry is what happens in the case if we add a 3rd postcopy subfeature; > > In your case we have three possibilities: > > > > a) Postcopy RAM only - 16 bytes > > b) Postcopy persistent-dirty-bitmap only - 0 bytes > > c) Both - 16 bytes > > > > Lets say we added postcopy-foo in the future and it wanted to add > > another 16 bytes, what would it send if it was foo+persistent-dirty-bitmap and no RAM? > > We'd end up with 16 bytes sent but you'd have to be very careful > > never to get that confused with case (a) above. > > > > (I don't feel too strongly about it though) > > Hmm.. Actually I use migrate_postcopy_ram() to distinct these thing in > loadvm_postcopy_handle_advise.. And it seem like it is a mistake. Are > migration capabilities available on target?.. On the other hand > postcopy-test doesn't fail... Libvirt does set it on the destination, and it's already useful for checking the destination host has the appropriate kernel userfault support; so I'm fine with requiring it. However it's good where possible to fail nicely if someone doesn't set it. Dave > > > > Dave > > > > > -- > > > Best regards, > > > Vladimir > > > > > -- > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK > > > -- > Best regards, > Vladimir > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK