Re: [PATCH v3] slab_arena: Enhance slab_arena_create to support madvise hints

[Cyrill Gorcunov <gorcunov@gmail.com>]

On Wed, May 15, 2019 at 03:37:56PM +0300, Vladimir Davydov wrote:
> 
> I'd also patch all places (tests, etc) where old flags (MAP_*) are used
> to switch them to new flags. Sooner or later we should drop this compat
> layer.

Maybe we should do this in a separate patch? I would like the tests to sit
for some time with MAP_ flags to make sure everything works. And I'll prepare
the patch covering MAP_ next week, sounds OK?

> > -#if !defined(MAP_ANONYMOUS)
> > -#define MAP_ANONYMOUS MAP_ANON
> > +static void
> > +madvise_checked(void *ptr, size_t size, int flags)
> > +{
> > +#ifdef TARANTOOL_SMALL_USE_MADVISE
> 
> It would be nice to have a warning in case MADV_DONTDUMP is unavailable.
> It should be printed only once. May be, here, or, even better, in
> Tarantool itself (via say_warn()).

You know I thought if we could use small/conf.h inside tarantool.
For this sake I prefixed symbols with TARANROOL_SMALL_ to not interfere
with any other symbols.

Another option -- provide something like

static const uint64_t small_features = (bitset of features);

bool small_have_feature(uint64_t mask)
{
	return small_features & mask;
}

?

> >  
> >  static void
> >  munmap_checked(void *addr, size_t size)
> >  {
> >  	if (munmap(addr, size)) {
> >  		char buf[64];
> > -		intptr_t ignore_it = (intptr_t)strerror_r(errno, buf,
> > -							  sizeof(buf));
> > +		char *ignore_it = strerror_r(errno, buf, sizeof(buf));
> 
> This wouldn't compile on OS X. Please leave it as is. Same's fair for
> madvise_checked.

The problem is that if I leave it as is it doesn't compile on linux,
due to _GNU_SOURCE definition, which is required for MADV_ flags :/