Re: [Qemu-devel] [PATCH v5 13/45] ram_debug_dump_bitmap: Dump a migration bitmap as text

[Dr. David Alan Gilbert]

* David Gibson (address@hidden) wrote:
> On Wed, Feb 25, 2015 at 04:51:36PM +0000, Dr. David Alan Gilbert (git) wrote:
> > From: "Dr. David Alan Gilbert" <address@hidden>
> > 
> > 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 <address@hidden>
> > ---
> >  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 91645cc..fe0df0d 100644
> > --- a/arch_init.c
> > +++ b/arch_init.c
> > @@ -776,6 +776,45 @@ 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 = 128;
> > +    char linebuf[129];
> > +
> > +    if (!todump) {
> > +        todump = migration_bitmap;
> 
> Any reason not to just have the caller pass migration_bitmap, if
> that's what they want?

migration_bitmap is a static in this file; I wanted to be
able to add calls to this debug function from elsewhere, e.g.
before aborts/crashes whereever I was testing things that
were going wrong.

> > +    }
> > +
> > +    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 = found || (thisbit != expected);
> > +        }
> > +        if (found) {
> > +            linebuf[curb] = '\0';
> > +            fprintf(stderr,  "0x%08" PRIx64 " : %s\n", cur, linebuf);
> 
> Might be slightly more readable if it printed GPAs instead of page
> numbers.

Indeed it would; but translating bitmap position into GPA is non-trivial
anyway; RAM blocks aren't necessarily in order within the bitmap
and indeed may be mixed on any one line.

Dave

> 
> > +        }
> > +    }
> > +}
> > +
> >  static int ram_save_setup(QEMUFile *f, void *opaque)
> >  {
> >      RAMBlock *block;
> > diff --git a/include/migration/migration.h b/include/migration/migration.h
> > index 5242ead..3776e86 100644
> > --- a/include/migration/migration.h
> > +++ b/include/migration/migration.h
> > @@ -156,6 +156,7 @@ uint64_t xbzrle_mig_pages_cache_miss(void);
> >  double xbzrle_mig_cache_miss_rate(void);
> >  
> >  void ram_handle_compressed(void *host, uint8_t ch, uint64_t size);
> > +void ram_debug_dump_bitmap(unsigned long *todump, bool expected);
> >  
> >  /**
> >   * @migrate_add_blocker - prevent migration from proceeding
> 
> -- 
> 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 / address@hidden / Manchester, UK