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authorDavid S. Miller <davem@davemloft.net>2005-04-17 18:03:09 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-17 18:03:09 -0700
commita9546f59e90d6ec1b65952c547302e0678e3a5ac (patch)
treed3660490ac539970b875a49c9032c5c946282cbf /arch
parenta4e884a311893b476893739901bed382cd62b4fe (diff)
downloadop-kernel-dev-a9546f59e90d6ec1b65952c547302e0678e3a5ac.zip
op-kernel-dev-a9546f59e90d6ec1b65952c547302e0678e3a5ac.tar.gz
[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>
Diffstat (limited to 'arch')
-rw-r--r--arch/sparc64/mm/init.c19
1 files changed, 15 insertions, 4 deletions
diff --git a/arch/sparc64/mm/init.c b/arch/sparc64/mm/init.c
index 89022cc..db6fa77 100644
--- a/arch/sparc64/mm/init.c
+++ b/arch/sparc64/mm/init.c
@@ -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)
{
- struct address_space *mapping = page_mapping(page);
- int dirty = test_bit(PG_dcache_dirty, &page->flags);
- int dirty_cpu = dcache_dirty_cpu(page);
- int this_cpu = get_cpu();
+ struct address_space *mapping;
+ int this_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)) {
+ int dirty = test_bit(PG_dcache_dirty, &page->flags);
if (dirty) {
+ int dirty_cpu = dcache_dirty_cpu(page);
+
if (dirty_cpu == this_cpu)
goto out;
smp_flush_dcache_page_impl(page, dirty_cpu);
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