Otto Moerbeek wrote:
> a future goal for malloc is to use multiple pools in threaded
> environments, to reduce lock contention.
>
> This is a small first step towards that goal: move two globals to the
> pool-specific struct dir_info. Currently there's only a single pool,
> but that will change one day.
>
> Lightly tested by myself on amd64, you can help by reviewing and
> testing this.
Thanks for this - I've been meaning to study the pool logic more.
One minor thing I noticed:
> Index: malloc.c
> ===================================================================
> RCS file: /cvs/src/lib/libc/stdlib/malloc.c,v
> retrieving revision 1.182
> diff -u -p -r1.182 malloc.c
> --- malloc.c 25 Feb 2016 00:38:51 -0000 1.182
> +++ malloc.c 9 Mar 2016 08:31:52 -0000
> @@ -93,13 +93,13 @@
> #define MQUERY(a, sz) mquery((a), (size_t)(sz), PROT_READ |
> PROT_WRITE, \
> MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, (off_t)0)
>
> -#define _MALLOC_LEAVE() if (__isthreaded) do { \
> - malloc_active--; \
> +#define _MALLOC_LEAVE(d) if (__isthreaded) do { \
> + (d)->active--; \
> _MALLOC_UNLOCK(); \
> } while (0)
> -#define _MALLOC_ENTER() if (__isthreaded) do { \
> +#define _MALLOC_ENTER(d) if (__isthreaded) do { \
> _MALLOC_LOCK(); \
> - malloc_active++; \
> + (d)->active++; \
> } while (0)
Are you sure these are guarded properly? I think the do-while block
should wrap the entire thing, including the if condition. Otherwise,
else conditions can still associate with the if.
