[v4,18/47] ram_debug_dump_bitmap: Dump a migration bitmap as text

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Misses out lines that are all the expected value so the output
can be quite compact depending on the circumstance.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 arch_init.c                   | 39 +++++++++++++++++++++++++++++++++++++++
 include/migration/migration.h |  1 +
 2 files changed, 40 insertions(+)

On Fri, Oct 03, 2014 at 06:47:24PM +0100, Dr. David Alan Gilbert (git) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Misses out lines that are all the expected value so the output
> can be quite compact depending on the circumstance.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> ---
>  arch_init.c                   | 39 +++++++++++++++++++++++++++++++++++++++
>  include/migration/migration.h |  1 +
>  2 files changed, 40 insertions(+)
> 
> diff --git a/arch_init.c b/arch_init.c
> index 772de36..6970733 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -769,6 +769,45 @@ static void reset_ram_globals(void)
>  
>  #define MAX_WAIT 50 /* ms, half buffered_file limit */
>  
> +/*
> + * 'expected' is the value you expect the bitmap mostly to be full
> + * of and it won't bother printing lines that are all this value
> + * if 'todump' is null the migration bitmap is dumped.
> + */
> +void ram_debug_dump_bitmap(unsigned long *todump, bool expected)
> +{
> +    int64_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS;
> +
> +    int64_t cur;
> +    int64_t linelen = 128l;

I don't think there's any point to the 'l' there.  "long" isn't
necessarily correct for an int64_t, and normal type promotion should
get this right anyway.

Assuming the user has a >128 character wide terminal seems a little
obnoxious, too.

> +    char linebuf[129];
> +
> +    if (!todump) {
> +        todump = migration_bitmap;
> +    }
> +
> +    for (cur = 0; cur < ram_pages; cur += linelen) {
> +        int64_t curb;
> +        bool found = false;
> +        /*
> +         * Last line; catch the case where the line length
> +         * is longer than remaining ram
> +         */
> +        if (cur+linelen > ram_pages) {
> +            linelen = ram_pages - cur;
> +        }
> +        for (curb = 0; curb < linelen; curb++) {
> +            bool thisbit = test_bit(cur+curb, todump);
> +            linebuf[curb] = thisbit ? '1' : '.';
> +            found |= (thisbit ^ expected);

I guess this will have the right result with the obvious encoding of a
bool, but I don't think it's conceptually correct.  It should be
logical, not bitwise operations so:
	found = found || (thisbit != expected);

* David Gibson (david@gibson.dropbear.id.au) wrote:
> On Fri, Oct 03, 2014 at 06:47:24PM +0100, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> > 
> > Misses out lines that are all the expected value so the output
> > can be quite compact depending on the circumstance.
> > 
> > Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  arch_init.c                   | 39 +++++++++++++++++++++++++++++++++++++++
> >  include/migration/migration.h |  1 +
> >  2 files changed, 40 insertions(+)
> > 
> > diff --git a/arch_init.c b/arch_init.c
> > index 772de36..6970733 100644
> > --- a/arch_init.c
> > +++ b/arch_init.c
> > @@ -769,6 +769,45 @@ static void reset_ram_globals(void)
> >  
> >  #define MAX_WAIT 50 /* ms, half buffered_file limit */
> >  
> > +/*
> > + * 'expected' is the value you expect the bitmap mostly to be full
> > + * of and it won't bother printing lines that are all this value
> > + * if 'todump' is null the migration bitmap is dumped.
> > + */
> > +void ram_debug_dump_bitmap(unsigned long *todump, bool expected)
> > +{
> > +    int64_t ram_pages = last_ram_offset() >> TARGET_PAGE_BITS;
> > +
> > +    int64_t cur;
> > +    int64_t linelen = 128l;
> 
> I don't think there's any point to the 'l' there.  "long" isn't
> necessarily correct for an int64_t, and normal type promotion should
> get this right anyway.

Fixed.

> Assuming the user has a >128 character wide terminal seems a little
> obnoxious, too.

This is a debug routine primarily to help me, but it seems right to leave
it in for the next person who has to debug it; it's easy enough for them
to tweak it to whatever their preference is.

> > +    char linebuf[129];
> > +
> > +    if (!todump) {
> > +        todump = migration_bitmap;
> > +    }
> > +
> > +    for (cur = 0; cur < ram_pages; cur += linelen) {
> > +        int64_t curb;
> > +        bool found = false;
> > +        /*
> > +         * Last line; catch the case where the line length
> > +         * is longer than remaining ram
> > +         */
> > +        if (cur+linelen > ram_pages) {
> > +            linelen = ram_pages - cur;
> > +        }
> > +        for (curb = 0; curb < linelen; curb++) {
> > +            bool thisbit = test_bit(cur+curb, todump);
> > +            linebuf[curb] = thisbit ? '1' : '.';
> > +            found |= (thisbit ^ expected);
> 
> I guess this will have the right result with the obvious encoding of a
> bool, but I don't think it's conceptually correct.  It should be
> logical, not bitwise operations so:
> 	found = found || (thisbit != expected);

Fixed.

Dave

> 
> -- 
> David Gibson			| I'll have my music baroque, and my code
> david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
> 				| _way_ _around_!
> http://www.ozlabs.org/~dgibson


--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK