Jan Beulich
2011-Oct-13 07:27 UTC
[Xen-devel] [PATCH] xmalloc: return unused full pages on multi-page allocations
Certain (boot time) allocations are relatively large (particularly when
building with high NR_CPUS), but can also happen to be pretty far away
from a power-of-two size. Utilize the page allocator''s (other than
Linux''es) capability of allowing to return space from higher-order
allocations in smaller pieces to return the unused parts immediately.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/common/xmalloc_tlsf.c
+++ b/xen/common/xmalloc_tlsf.c
@@ -527,13 +527,21 @@ static void xmalloc_pool_put(void *p)
static void *xmalloc_whole_pages(unsigned long size)
{
struct bhdr *b;
- unsigned int pageorder = get_order_from_bytes(size + BHDR_OVERHEAD);
+ unsigned int i, pageorder = get_order_from_bytes(size + BHDR_OVERHEAD);
+ char *p;
b = alloc_xenheap_pages(pageorder, 0);
if ( b == NULL )
return NULL;
- b->size = (1 << (pageorder + PAGE_SHIFT));
+ b->size = PAGE_ALIGN(size + BHDR_OVERHEAD);
+ for ( p = (char *)b + b->size, i = 0; i < pageorder; ++i )
+ if ( (unsigned long)p & (PAGE_SIZE << i) )
+ {
+ free_xenheap_pages(p, i);
+ p += PAGE_SIZE << i;
+ }
+
return (void *)b->ptr.buffer;
}
@@ -611,7 +619,20 @@ void xfree(void *p)
}
if ( b->size >= PAGE_SIZE )
- free_xenheap_pages((void *)b, get_order_from_bytes(b->size));
+ {
+ unsigned int i, order = get_order_from_bytes(b->size);
+
+ BUG_ON((unsigned long)b & ((PAGE_SIZE << order) - 1));
+ for ( i = 0; ; ++i )
+ {
+ if ( !(b->size & (PAGE_SIZE << i)) )
+ continue;
+ b->size -= PAGE_SIZE << i;
+ free_xenheap_pages((void *)b + b->size, i);
+ if ( i + 1 >= order )
+ break;
+ }
+ }
else
xmem_pool_free(p, xenpool);
}
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Keir Fraser
2011-Oct-13 07:46 UTC
Re: [Xen-devel] [PATCH] xmalloc: return unused full pages on multi-page allocations
On 13/10/2011 08:27, "Jan Beulich" <JBeulich@suse.com> wrote:> Certain (boot time) allocations are relatively large (particularly when > building with high NR_CPUS), but can also happen to be pretty far away > from a power-of-two size. Utilize the page allocator''s (other than > Linux''es) capability of allowing to return space from higher-order > allocations in smaller pieces to return the unused parts immediately. > > Signed-off-by: Jan Beulich <jbeulich@suse.com>Acked-by: Keir Fraser <keir@xen.org>> --- a/xen/common/xmalloc_tlsf.c > +++ b/xen/common/xmalloc_tlsf.c > @@ -527,13 +527,21 @@ static void xmalloc_pool_put(void *p) > static void *xmalloc_whole_pages(unsigned long size) > { > struct bhdr *b; > - unsigned int pageorder = get_order_from_bytes(size + BHDR_OVERHEAD); > + unsigned int i, pageorder = get_order_from_bytes(size + BHDR_OVERHEAD); > + char *p; > > b = alloc_xenheap_pages(pageorder, 0); > if ( b == NULL ) > return NULL; > > - b->size = (1 << (pageorder + PAGE_SHIFT)); > + b->size = PAGE_ALIGN(size + BHDR_OVERHEAD); > + for ( p = (char *)b + b->size, i = 0; i < pageorder; ++i ) > + if ( (unsigned long)p & (PAGE_SIZE << i) ) > + { > + free_xenheap_pages(p, i); > + p += PAGE_SIZE << i; > + } > + > return (void *)b->ptr.buffer; > } > > @@ -611,7 +619,20 @@ void xfree(void *p) > } > > if ( b->size >= PAGE_SIZE ) > - free_xenheap_pages((void *)b, get_order_from_bytes(b->size)); > + { > + unsigned int i, order = get_order_from_bytes(b->size); > + > + BUG_ON((unsigned long)b & ((PAGE_SIZE << order) - 1)); > + for ( i = 0; ; ++i ) > + { > + if ( !(b->size & (PAGE_SIZE << i)) ) > + continue; > + b->size -= PAGE_SIZE << i; > + free_xenheap_pages((void *)b + b->size, i); > + if ( i + 1 >= order ) > + break; > + } > + } > else > xmem_pool_free(p, xenpool); > } > > > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel