Re: [Qemu-devel] [PATCH v3 2/5] util: introduce threaded workqueue

[Emilio G. Cota]

On Mon, Nov 26, 2018 at 15:57:25 +0800, Xiao Guangrong wrote:
> 
> 
> On 11/23/18 7:02 PM, Dr. David Alan Gilbert wrote:
> 
> > > +#include "qemu/osdep.h"
> > > +#include "qemu/bitmap.h"
> > > +#include "qemu/threaded-workqueue.h"
> > > +
> > > +#define SMP_CACHE_BYTES 64
> > 
> > That's architecture dependent isn't it?
> > 
> 
> Yes, it's arch dependent indeed.
> 
> I just used 64 for simplification and i think it is <= 64 on most CPU arch-es
> so that can work.
> 
> Should i introduce statically defined CACHE LINE SIZE for all arch-es? :(

No, at compile-time this is impossible to know.

We do query this info at run-time though (see util/cacheinfo.c),
but using that info here would complicate things too much.

You can just give it a different name, and perhaps add a comment.
See for instance what we do in qht.c with QHT_BUCKET_ALIGN.

Thanks,

                Emilio