For the set of 3:
Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
* Peter Xu (pet...@redhat.com) wrote:
> On Tue, Sep 20, 2022 at 08:47:20PM -0400, Peter Xu wrote:
> > On Tue, Sep 20, 2022 at 06:52:27PM -0400, Peter Xu wrote:
> > > With the new code to send pages in rp-return thread, there's little help
> > > to
> > > keep lots of the old code on maintaining the preempt state in migration
> > > thread, because the new way should always be faster..
> > >
> > > Then if we'll always send pages in the rp-return thread anyway, we don't
> > > need those logic to maintain preempt state anymore because now we
> > > serialize
> > > things using the mutex directly instead of using those fields.
> > >
> > > It's very unfortunate to have those code for a short period, but that's
> > > still one intermediate step that we noticed the next bottleneck on the
> > > migration thread. Now what we can do best is to drop unnecessary code as
> > > long as the new code is stable to reduce the burden. It's actually a good
> > > thing because the new "sending page in rp-return thread" model is (IMHO)
> > > even cleaner and with better performance.
> > >
> > > Remove the old code that was responsible for maintaining preempt states,
> > > at
> > > the meantime also remove x-postcopy-preempt-break-huge parameter because
> > > with concurrent sender threads we don't really need to break-huge anymore.
> > >
> > > Signed-off-by: Peter Xu <pet...@redhat.com>
> > > ---
> > > migration/migration.c | 2 -
> > > migration/ram.c | 258 +-----------------------------------------
> > > 2 files changed, 3 insertions(+), 257 deletions(-)
> > >
> > > diff --git a/migration/migration.c b/migration/migration.c
> > > index fae8fd378b..698fd94591 100644
> > > --- a/migration/migration.c
> > > +++ b/migration/migration.c
> > > @@ -4399,8 +4399,6 @@ static Property migration_properties[] = {
> > > DEFINE_PROP_SIZE("announce-step", MigrationState,
> > > parameters.announce_step,
> > > DEFAULT_MIGRATE_ANNOUNCE_STEP),
> > > - DEFINE_PROP_BOOL("x-postcopy-preempt-break-huge", MigrationState,
> > > - postcopy_preempt_break_huge, true),
> >
> > Forgot to drop the variable altogether:
> >
> > diff --git a/migration/migration.h b/migration/migration.h
> > index cdad8aceaa..ae4ffd3454 100644
> > --- a/migration/migration.h
> > +++ b/migration/migration.h
> > @@ -340,13 +340,6 @@ struct MigrationState {
> > bool send_configuration;
> > /* Whether we send section footer during migration */
> > bool send_section_footer;
> > - /*
> > - * Whether we allow break sending huge pages when postcopy preempt is
> > - * enabled. When disabled, we won't interrupt precopy within sending a
> > - * host huge page, which is the old behavior of vanilla postcopy.
> > - * NOTE: this parameter is ignored if postcopy preempt is not enabled.
> > - */
> > - bool postcopy_preempt_break_huge;
> >
> > /* Needed by postcopy-pause state */
> > QemuSemaphore postcopy_pause_sem;
> >
> > Will squash this in in next version.
>
> Two more varialbes to drop, as attached..
>
>
> --
> Peter Xu
> From b3308e34398e21c19bd36ec21aae9c7f9f623d75 Mon Sep 17 00:00:00 2001
> From: Peter Xu <pet...@redhat.com>
> Date: Wed, 21 Sep 2022 09:51:55 -0400
> Subject: [PATCH] fixup! migration: Remove old preempt code around state
> maintainance
> Content-type: text/plain
>
> Signed-off-by: Peter Xu <pet...@redhat.com>
> ---
> migration/ram.c | 33 ---------------------------------
> 1 file changed, 33 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index 03bf2324ab..2599eee070 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -97,28 +97,6 @@ struct PageSearchStatus {
> unsigned long page;
> /* Set once we wrap around */
> bool complete_round;
> - /*
> - * [POSTCOPY-ONLY] Whether current page is explicitly requested by
> - * postcopy. When set, the request is "urgent" because the dest QEMU
> - * threads are waiting for us.
> - */
> - bool postcopy_requested;
> - /*
> - * [POSTCOPY-ONLY] The target channel to use to send current page.
> - *
> - * Note: This may _not_ match with the value in postcopy_requested
> - * above. Let's imagine the case where the postcopy request is exactly
> - * the page that we're sending in progress during precopy. In this case
> - * we'll have postcopy_requested set to true but the target channel
> - * will be the precopy channel (so that we don't split brain on that
> - * specific page since the precopy channel already contains partial of
> - * that page data).
> - *
> - * Besides that specific use case, postcopy_target_channel should
> - * always be equal to postcopy_requested, because by default we send
> - * postcopy pages via postcopy preempt channel.
> - */
> - bool postcopy_target_channel;
> /* Whether we're sending a host page */
> bool host_page_sending;
> /* The start/end of current host page. Invalid if
> host_page_sending==false */
> @@ -1573,13 +1551,6 @@ retry:
> */
> static bool find_dirty_block(RAMState *rs, PageSearchStatus *pss, bool
> *again)
> {
> - /*
> - * This is not a postcopy requested page, mark it "not urgent", and use
> - * precopy channel to send it.
> - */
> - pss->postcopy_requested = false;
> - pss->postcopy_target_channel = RAM_CHANNEL_PRECOPY;
> -
> /* Update pss->page for the next dirty bit in ramblock */
> pss_find_next_dirty(pss);
>
> @@ -2091,9 +2062,6 @@ static bool get_queued_page(RAMState *rs,
> PageSearchStatus *pss)
> * really rare.
> */
> pss->complete_round = false;
> - /* Mark it an urgent request, meanwhile using POSTCOPY channel */
> - pss->postcopy_requested = true;
> - pss->postcopy_target_channel = RAM_CHANNEL_POSTCOPY;
> }
>
> return !!block;
> @@ -2190,7 +2158,6 @@ int ram_save_queue_pages(const char *rbname, ram_addr_t
> start, ram_addr_t len)
> * we should be the only one who operates on the qemufile
> */
> pss->pss_channel = migrate_get_current()->postcopy_qemufile_src;
> - pss->postcopy_requested = true;
> assert(pss->pss_channel);
>
> /*
> --
> 2.32.0
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
