Re: [Qemu-devel] [PATCH v2 23/29] Include less of the generated modular QAPI headers

[Eric Blake]

On 02/11/2018 03:36 AM, Markus Armbruster wrote:
> In my "build everything" tree, a change to the types in
> qapi-schema.json triggers a recompile of about 4800 out of 5100
> objects.
>
> The previous commit split up qmp-commands.h, qmp-event.h, qmp-visit.h,
> qapi-types.h.  Each of these headers still includes all its shards.
> Reduce compile time by including just the shards we actually need.
>
> To illustrate the benefits: adding a type to qapi/migration.json now
> recompiles some 2300 instead of 4800 objects.  The next commit will
> improve it further.
>
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>   backends/cryptodev.c             |  1 -
>   backends/hostmem.c               |  3 ++-

How did you determine which shards to include where? Remove all shards, 
try compiling, and see what fails, then add back in the right includes? 
Or was it scripted somehow?  (Trying to figure out, in case I have to 
rebase this patch)

> +++ b/block/crypto.c
> @@ -24,9 +24,9 @@
>   #include "sysemu/block-backend.h"
>   #include "crypto/block.h"
>   #include "qapi/opts-visitor.h"
> +#include "qapi/qapi-visit-crypto.h"
>   #include "qapi/qmp/qdict.h"
>   #include "qapi/qobject-input-visitor.h"
> -#include "qapi-visit.h"
>   #include "qapi/error.h"

Any rhyme or reason to the resulting include order that I should be 
looking for (we aren't alphabetical in general, but if your changes were 
trying to honor a particular pattern among the few affected lines, 
that's useful to know).

> +++ b/scripts/qapi/commands.py

The non-mechanical portion of the patch :)

> @@ -241,6 +241,9 @@ class 
> QAPISchemaGenCommandVisitor(QAPISchemaModularCVisitor):
>   
>       def _begin_module(self, name):
>           self._visited_ret_types[self._genc] = set()
> +        commands = self._module_basename('qapi-commands', name)
> +        types = self._module_basename('qapi-types', name)
> +        visit = self._module_basename('qapi-visit', name)
>           self._genc.add(mcgen('''
>   #include "qemu/osdep.h"
>   #include "qemu-common.h"
> @@ -251,18 +254,17 @@ class 
> QAPISchemaGenCommandVisitor(QAPISchemaModularCVisitor):
>   #include "qapi/qobject-input-visitor.h"
>   #include "qapi/dealloc-visitor.h"
>   #include "qapi/error.h"
> -#include "%(prefix)sqapi-types.h"
> -#include "%(prefix)sqapi-visit.h"
> -#include "%(prefix)sqmp-commands.h"
> +#include "%(visit)s.h"
> +#include "%(commands)s.h"
>   
>   ''',
> -                             prefix=self._prefix))
> +                             commands=commands, visit=visit))
>           self._genh.add(mcgen('''
> -#include "%(prefix)sqapi-types.h"
> +#include "%(types)s.h"
>   #include "qapi/qmp/dispatch.h"
>   
>   ''',
> -                             prefix=self._prefix))
> +                             types=types))

Makes sense.

The compiler will catch anything we did wrong.

Reviewed-by: Eric Blake <address@hidden>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org