[v20210701,03/40] xl: fix description of migrate --debug

Commit Message

Olaf Hering July 1, 2021, 9:55 a.m. UTC

xl migrate --debug used to track every pfn in every batch of pages.
But these times are gone. The code in xc_domain_save is the consumer
of this knob, but it considers it only for the remus and colo case.

Adjust the help text to tell what --debug does today: Nothing.

Signed-off-by: Olaf Hering <[e-mail]>
Reviewed-by: Juergen Gross <[e-mail]>

v02:
- the option has no effect anymore
---
 docs/man/xl.1.pod.in   | 2 +-
 tools/xl/xl_cmdtable.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

Comments

Anthony PERARD July 1, 2021, 2:30 p.m. UTC | #1

On Thu, Jul 01, 2021 at 11:55:58AM +0200, Olaf Hering wrote:
> xl migrate --debug used to track every pfn in every batch of pages.
> But these times are gone. The code in xc_domain_save is the consumer
> of this knob, but it considers it only for the remus and colo case.
> 
> Adjust the help text to tell what --debug does today: Nothing.
> 
> Signed-off-by: Olaf Hering <[e-mail]>
> Reviewed-by: Juergen Gross <[e-mail]>
> 
> v02:
> - the option has no effect anymore

Acked-by: Anthony PERARD <[e-mail]>

Thanks,

Andrew Cooper July 1, 2021, 2:33 p.m. UTC | #2

On 01/07/2021 10:55, Olaf Hering wrote:
> xl migrate --debug used to track every pfn in every batch of pages.
> But these times are gone. The code in xc_domain_save is the consumer
> of this knob, but it considers it only for the remus and colo case.
>
> Adjust the help text to tell what --debug does today: Nothing.
>
> Signed-off-by: Olaf Hering <[e-mail]>
> Reviewed-by: Juergen Gross <[e-mail]>
>
> v02:
> - the option has no effect anymore

Since when?  It was absolutely critical to debugging issues during the
development of migration v2.

~Andrew

Olaf Hering July 1, 2021, 2:40 p.m. UTC | #3

Am Thu, 1 Jul 2021 15:33:47 +0100
schrieb Andrew Cooper <[e-mail]>:

> Since when?  It was absolutely critical to debugging issues during the
> development of migration v2.

Well, I can find out if needed.
What could would it enable today?
Last time I looked there was none.

Olaf

Olaf Hering July 1, 2021, 2:41 p.m. UTC | #4

Am Thu, 1 Jul 2021 16:40:55 +0200
schrieb Olaf Hering <[e-mail]>:

> could

"code", sorry.

Olaf

Andrew Cooper July 1, 2021, 2:49 p.m. UTC | #5

On 01/07/2021 15:41, Olaf Hering wrote:
> Am Thu, 1 Jul 2021 16:40:55 +0200
> schrieb Olaf Hering <[e-mail]>:
>
>> could
> "code", sorry.

c/s 7449fb36c6c81d2ba10a40b59e61a9f420cd8450 was buggy and inverted the
condition while making the code transformation.

--debug makes no sense at all in a checkpointed stream.

~Andrew

Olaf Hering July 1, 2021, 3:08 p.m. UTC | #6

Am Thu, 1 Jul 2021 15:49:08 +0100
schrieb Andrew Cooper <[e-mail]>:

> --debug makes no sense at all in a checkpointed stream.

This should probably have become "ctx->save.checkpointed == MIG_STREAM_NONE".

But this still leaves the question what value this code branch has when verify_frames does not, and most likely can not, work.
I think fixing it requires to expose details like which pages are grant pages.

Olaf

Patch

diff --git a/docs/man/xl.1.pod.in b/docs/man/xl.1.pod.in
index e2176bd696..70a6ebf438 100644
--- a/docs/man/xl.1.pod.in
+++ b/docs/man/xl.1.pod.in
@@ -481,7 +481,7 @@  domain.
 
 =item B<--debug>
 
-Display huge (!) amount of debug information during the migration process.
+This option has no effect. It is preserved for compatibility reasons.
 
 =item B<-p>
 
diff --git a/tools/xl/xl_cmdtable.c b/tools/xl/xl_cmdtable.c
index 661323d488..ca1dfa3525 100644
--- a/tools/xl/xl_cmdtable.c
+++ b/tools/xl/xl_cmdtable.c
@@ -172,7 +172,7 @@  const struct cmd_spec cmd_table[] = {
       "                migrate-receive [-d -e]\n"
       "-e              Do not wait in the background (on <host>) for the death\n"
       "                of the domain.\n"
-      "--debug         Print huge (!) amount of debug during the migration process.\n"
+      "--debug         Ignored.\n"
       "-p              Do not unpause domain after migrating it.\n"
       "-D              Preserve the domain id"
     },