@@ -972,6 +972,54 @@ release_pages (void)
page_entry *p, *start_p;
char *start;
size_t len;
+ size_t mapped_len;
+ page_entry *next, *prev, *newprev;
+ size_t free_unit = (GGC_QUIRE_SIZE/2) * G.pagesize;
+
+ /* First free larger continuous areas to the OS.
+ This allows other allocators to grab these areas if needed.
+ This is only done on larger chunks to avoid fragmentation.
+ This does not always work because the free_pages list is only
+ sorted over a single GC cycle. */
+
+ p = G.free_pages;
+ prev = NULL;
+ while (p)
+ {
+ start = p->page;
+ start_p = p;
+ len = 0;
+ mapped_len = 0;
+ newprev = prev;
+ while (p && p->page == start + len)
+ {
+ len += p->bytes;
+ if (!p->discarded)
+ mapped_len += p->bytes;
+ newprev = p;
+ p = p->next;
+ }
+ if (len >= free_unit)
+ {
+ while (start_p != p)
+ {
+ next = start_p->next;
+ free (start_p);
+ start_p = next;
+ }
+ munmap (start, len);
+ if (prev)
+ prev->next = p;
+ else
+ G.free_pages = p;
+ G.bytes_mapped -= mapped_len;
+ continue;
+ }
+ prev = newprev;
+ }
+
+ /* Now give back the fragmented pages to the OS, but keep the address
+ space to reuse it next time. */
for (p = G.free_pages; p; )
{
From: Andi Kleen <ak@linux.intel.com> This implements the freeing back of large chunks in the ggc madvise path Richard Guenther asked for. This way on systems with limited address space malloc() and other allocators still have a chance to get back at some of the memory ggc freed. The fragmented pages are still just given back, but the address space stays allocated. I tried freeing only aligned 2MB areas to optimize for 2MB huge pages, but the hit rate was quite low, so I switched to 1MB+ unaligned areas. Passed bootstrap and testing on x86_64-linux v2: Hardcode free unit size instead of param gcc/: 2011-10-18 Andi Kleen <ak@linux.intel.com> * ggc-page (release_pages): First free large continuous chunks in the madvise path. --- gcc/ggc-page.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 48 insertions(+), 0 deletions(-)