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authorJohn Dykstra <jdykstra@cray.com>2012-05-25 16:12:46 -0500
committerIngo Molnar <mingo@kernel.org>2012-05-30 10:57:11 +0200
commitfa83523f45fbb403eba4ebc5704bf98aa4da0163 (patch)
tree35466e5e2e9e5ed8171ef596d63690ed42621fca /arch
parent1b38a3a10f2ad96a3c0130f63b7f3610bab7090d (diff)
downloadlinux-fa83523f45fbb403eba4ebc5704bf98aa4da0163.tar.gz
x86/mm/pat: Improve scaling of pat_pagerange_is_ram()
Function pat_pagerange_is_ram() scales poorly to large address ranges, because it probes the resource tree for each page. On a 2.6 GHz Opteron, this function consumes 34 ms for a 1 GB range. It is called twice during untrack_pfn_vma(), slowing process cleanup and handicapping the OOM killer. This replacement consumes less than 1ms, under the same conditions. Signed-off-by: John Dykstra <jdykstra@cray.com> on behalf of Cray Inc. Acked-by: Suresh Siddha <suresh.b.siddha@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1337980366.1979.6.camel@redwood [ Small stylistic cleanups and renames ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/mm/pat.c56
1 files changed, 36 insertions, 20 deletions
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index f6ff57b7efa..bea6e573e02 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -158,31 +158,47 @@ static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type)
return req_type;
}
+struct pagerange_state {
+ unsigned long cur_pfn;
+ int ram;
+ int not_ram;
+};
+
+static int
+pagerange_is_ram_callback(unsigned long initial_pfn, unsigned long total_nr_pages, void *arg)
+{
+ struct pagerange_state *state = arg;
+
+ state->not_ram |= initial_pfn > state->cur_pfn;
+ state->ram |= total_nr_pages > 0;
+ state->cur_pfn = initial_pfn + total_nr_pages;
+
+ return state->ram && state->not_ram;
+}
+
static int pat_pagerange_is_ram(resource_size_t start, resource_size_t end)
{
- int ram_page = 0, not_rampage = 0;
- unsigned long page_nr;
+ int ret = 0;
+ unsigned long start_pfn = start >> PAGE_SHIFT;
+ unsigned long end_pfn = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ struct pagerange_state state = {start_pfn, 0, 0};
- for (page_nr = (start >> PAGE_SHIFT); page_nr < (end >> PAGE_SHIFT);
- ++page_nr) {
- /*
- * For legacy reasons, physical address range in the legacy ISA
- * region is tracked as non-RAM. This will allow users of
- * /dev/mem to map portions of legacy ISA region, even when
- * some of those portions are listed(or not even listed) with
- * different e820 types(RAM/reserved/..)
- */
- if (page_nr >= (ISA_END_ADDRESS >> PAGE_SHIFT) &&
- page_is_ram(page_nr))
- ram_page = 1;
- else
- not_rampage = 1;
-
- if (ram_page == not_rampage)
- return -1;
+ /*
+ * For legacy reasons, physical address range in the legacy ISA
+ * region is tracked as non-RAM. This will allow users of
+ * /dev/mem to map portions of legacy ISA region, even when
+ * some of those portions are listed(or not even listed) with
+ * different e820 types(RAM/reserved/..)
+ */
+ if (start_pfn < ISA_END_ADDRESS >> PAGE_SHIFT)
+ start_pfn = ISA_END_ADDRESS >> PAGE_SHIFT;
+
+ if (start_pfn < end_pfn) {
+ ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn,
+ &state, pagerange_is_ram_callback);
}
- return ram_page;
+ return (ret > 0) ? -1 : (state.ram ? 1 : 0);
}
/*