Re: [PATCH 4/5] kmemtrace: SLUB hooks.

Pekka Enberg
2008-08-11T14:16:17Z

On Mon, 2008-08-11 at 09:13 -0500, Christoph Lameter wrote:
> Pekka Enberg wrote:
> > On Mon, 2008-08-11 at 09:04 -0500, Christoph Lameter wrote:
> >> Eduard - Gabriel Munteanu wrote:
> >>
> >>
> >>
> >>> static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
> >>> {
> >>> + void *ret;
> >>> +
> >>> if (__builtin_constant_p(size) &&
> >>> size <= PAGE_SIZE && !(flags & SLUB_DMA)) {
> >>> struct kmem_cache *s = kmalloc_slab(size);
> >>> @@ -239,7 +280,13 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
> >>> if (!s)
> >>> return ZERO_SIZE_PTR;
> >>>
> >>> - return kmem_cache_alloc_node(s, flags, node);
> >>> + ret = kmem_cache_alloc_node_notrace(s, flags, node);
> >>> +
> >>> + kmemtrace_mark_alloc_node(KMEMTRACE_TYPE_KMALLOC,
> >>> + _THIS_IP_, ret,
> >>> + size, s->size, flags, node);
> >>> +
> >>> + return ret;
> >> You could simplify the stuff in slub.h if you would fall back to the uninlined
> >> functions in the case that kmemtrace is enabled. IMHO adding additional inline
> >> code here does grow these function to a size where inlining is not useful anymore.
> >
> > So, if CONFIG_KMEMTRACE is enabled, make the inlined version go away
> > completely? I'm okay with that though I wonder if that means we now take
> > a performance hit when CONFIG_KMEMTRACE is enabled but tracing is
> > disabled at run-time...
>
> We already take a performance hit because of the additional function calls.
>
> With the above approach the kernel binary will grow significantly because you
> are now inserting an additional function call at all call sites.

The function call is supposed to go away when we convert kmemtrace to
use Mathieu's markers but I suppose even then we have a problem with
inlining?