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authorRobin Holt <holt@sgi.com>2010-04-23 10:36:22 -0500
committerH. Peter Anvin <hpa@zytor.com>2010-04-23 15:57:23 -0700
commit1f9cc3cb6a27521edfe0a21abf97d2bb11c4d237 (patch)
treec9af6a71398aed690c1fa813498a0aed8abf2d7b /arch/x86/mm/pat.c
parent4daa2a8093ecd1148270a1fc64e99f072b8c2901 (diff)
x86, pat: Update the page flags for memtype atomically instead of using memtype_lock
While testing an application using the xpmem (out of kernel) driver, we noticed a significant page fault rate reduction of x86_64 with respect to ia64. For one test running with 32 cpus, one thread per cpu, it took 01:08 for each of the threads to vm_insert_pfn 2GB worth of pages. For the same test running on 256 cpus, one thread per cpu, it took 14:48 to vm_insert_pfn 2 GB worth of pages. The slowdown was tracked to lookup_memtype which acquires the spinlock memtype_lock. This heavily contended lock was slowing down vm_insert_pfn(). With the cmpxchg on page->flags method, both the 32 cpu and 256 cpu cases take approx 00:01.3 seconds to complete. Signed-off-by: Robin Holt <holt@sgi.com> LKML-Reference: <20100423153627.751194346@gulag1.americas.sgi.com> Cc: Venkatesh Pallipadi <venkatesh.pallipadi@gmail.com> Cc: Rafael Wysocki <rjw@novell.com> Reviewed-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/mm/pat.c')
-rw-r--r--arch/x86/mm/pat.c8
1 files changed, 0 insertions, 8 deletions
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 951011166ef5..501fc60e5e4d 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -190,8 +190,6 @@ static int pat_pagerange_is_ram(unsigned long start, unsigned long end)
* Here we do two pass:
* - Find the memtype of all the pages in the range, look for any conflicts
* - In case of no conflicts, set the new memtype for pages in the range
- *
- * Caller must hold memtype_lock for atomicity.
*/
static int reserve_ram_pages_type(u64 start, u64 end, unsigned long req_type,
unsigned long *new_type)
@@ -297,9 +295,7 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
is_range_ram = pat_pagerange_is_ram(start, end);
if (is_range_ram == 1) {
- spin_lock(&memtype_lock);
err = reserve_ram_pages_type(start, end, req_type, new_type);
- spin_unlock(&memtype_lock);
return err;
} else if (is_range_ram < 0) {
@@ -351,9 +347,7 @@ int free_memtype(u64 start, u64 end)
is_range_ram = pat_pagerange_is_ram(start, end);
if (is_range_ram == 1) {
- spin_lock(&memtype_lock);
err = free_ram_pages_type(start, end);
- spin_unlock(&memtype_lock);
return err;
} else if (is_range_ram < 0) {
@@ -394,10 +388,8 @@ static unsigned long lookup_memtype(u64 paddr)
if (pat_pagerange_is_ram(paddr, paddr + PAGE_SIZE)) {
struct page *page;
- spin_lock(&memtype_lock);
page = pfn_to_page(paddr >> PAGE_SHIFT);
rettype = get_page_memtype(page);
- spin_unlock(&memtype_lock);
/*
* -1 from get_page_memtype() implies RAM page is in its
* default state and not reserved, and hence of type WB