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Re: [PATCH 5/6] migration/postcopy: enable random order target page arri
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH 5/6] migration/postcopy: enable random order target page arrival |
Date: |
Thu, 7 Nov 2019 09:14:05 +0000 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
* Wei Yang (address@hidden) wrote:
> On Wed, Nov 06, 2019 at 08:08:28PM +0000, Dr. David Alan Gilbert wrote:
> >* Wei Yang (address@hidden) wrote:
> >> After using number of target page received to track one host page, we
> >> could have the capability to handle random order target page arrival in
> >> one host page.
> >>
> >> This is a preparation for enabling compress during postcopy.
> >>
> >> Signed-off-by: Wei Yang <address@hidden>
> >> ---
> >> migration/ram.c | 16 +++-------------
> >> 1 file changed, 3 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/migration/ram.c b/migration/ram.c
> >> index b5759793a9..da0596411c 100644
> >> --- a/migration/ram.c
> >> +++ b/migration/ram.c
> >> @@ -4015,7 +4015,6 @@ static int ram_load_postcopy(QEMUFile *f)
> >> MigrationIncomingState *mis = migration_incoming_get_current();
> >> /* Temporary page that is later 'placed' */
> >> void *postcopy_host_page = mis->postcopy_tmp_page;
> >> - void *last_host = NULL;
> >> bool all_zero = false;
> >> int target_pages = 0;
> >>
> >> @@ -4062,24 +4061,15 @@ static int ram_load_postcopy(QEMUFile *f)
> >> * that's moved into place later.
> >> * The migration protocol uses, possibly smaller,
> >> target-pages
> >> * however the source ensures it always sends all the
> >> components
> >> - * of a host page in order.
> >> + * of a host page in one chunk.
> >> */
> >> page_buffer = postcopy_host_page +
> >> ((uintptr_t)host & (block->page_size - 1));
> >> /* If all TP are zero then we can optimise the place */
> >> if (target_pages == 1) {
> >> all_zero = true;
> >> - } else {
> >> - /* not the 1st TP within the HP */
> >> - if (host != (last_host + TARGET_PAGE_SIZE)) {
> >> - error_report("Non-sequential target page %p/%p",
> >> - host, last_host);
> >> - ret = -EINVAL;
> >> - break;
> >> - }
> >
> >I think this is losing more protection than needed.
> >I think you can still protect against a page from a different host-page
> >arriving until we've placed the current host-page.
> >So something like:
> >
> > if (((uintptr_t)host & ~(block->page_size - 1)) !=
> > last_host)
> >
>
> OK, looks reasonable.
>
> >and then set last_host to the start of the host page.
> >
>
> I think it is not necessary to update the last_host on each target page. We
> can just set it at the first target page.
Yes, that would be fine.
Dave
> >Then you'll check if that flush is really working.
> >
> >Dave
> >
> >> }
> >>
> >> -
> >> /*
> >> * If it's the last part of a host page then we place the host
> >> * page
> >> @@ -4090,7 +4080,6 @@ static int ram_load_postcopy(QEMUFile *f)
> >> }
> >> place_source = postcopy_host_page;
> >> }
> >> - last_host = host;
> >>
> >> switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
> >> case RAM_SAVE_FLAG_ZERO:
> >> @@ -4143,7 +4132,8 @@ static int ram_load_postcopy(QEMUFile *f)
> >>
> >> if (!ret && place_needed) {
> >> /* This gets called at the last target page in the host page
> >> */
> >> - void *place_dest = host + TARGET_PAGE_SIZE - block->page_size;
> >> + void *place_dest = (void *)QEMU_ALIGN_DOWN((unsigned
> >> long)host,
> >> + block->page_size);
> >>
> >> if (all_zero) {
> >> ret = postcopy_place_page_zero(mis, place_dest,
> >> --
> >> 2.17.1
> >>
> >--
> >Dr. David Alan Gilbert / address@hidden / Manchester, UK
>
> --
> Wei Yang
> Help you, Help me
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK