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[PATCH] sparc64: Do not flush dcache for ZERO_PAGE. 

This case actually can get exercised a lot during an ELF
coredump of a process which contains a lot of non-COW'd
anonymous pages.  GDB has this test case which in partiaular
creates near terabyte process full of ZERO_PAGEes.  It takes
forever to just walk through the page tables because of
all of these spurious cache flushes on sparc64.

With this change it takes only a second or so.

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
David S. Miller 2005-04-17 18:03:09 -07:00 committed by Linus Torvalds
parent a4e884a311
commit a9546f59e9
1 changed files with 15 additions and 4 deletions
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19
arch/sparc64/mm/init.c
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@ -201,13 +201,24 @@ void update_mmu_cache(struct vm_area_struct *vma, unsigned long address, pte_t p
void flush_dcache_page(struct page *page) void flush_dcache_page(struct page *page)
{ {
struct address_space *mapping = page_mapping(page); struct address_space *mapping;
int dirty = test_bit(PG_dcache_dirty, &page->flags); int this_cpu;
int dirty_cpu = dcache_dirty_cpu(page);
int this_cpu = get_cpu();
/* Do not bother with the expensive D-cache flush if it
* is merely the zero page. The 'bigcore' testcase in GDB
* causes this case to run millions of times.
*/
if (page == ZERO_PAGE(0))
return;
this_cpu = get_cpu();
mapping = page_mapping(page);
if (mapping && !mapping_mapped(mapping)) { if (mapping && !mapping_mapped(mapping)) {
int dirty = test_bit(PG_dcache_dirty, &page->flags);
if (dirty) { if (dirty) {
int dirty_cpu = dcache_dirty_cpu(page);
if (dirty_cpu == this_cpu) if (dirty_cpu == this_cpu)
goto out; goto out;
smp_flush_dcache_page_impl(page, dirty_cpu); smp_flush_dcache_page_impl(page, dirty_cpu);