Le 06/03/2018 à 14:25, Nicholas Piggin a écrit :
Rather than build slice masks from a range then use that to check for
fit in a candidate mask, implement slice_check_range_fits that checks
if a range fits in a mask directly.
This allows several structures to be removed from stacks, and also we
don't expect a huge range in a lot of these cases, so building and
comparing a full mask is going to be more expensive than testing just
one or two bits of the range.
On POWER8, this increases vfork+exec+exit performance by 0.3%
and reduces time to mmap+munmap a 64kB page by 5%.
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
arch/powerpc/mm/slice.c | 63 ++++++++++++++++++++++++++-----------------------
1 file changed, 34 insertions(+), 29 deletions(-)
diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 2115efe5e869..3841fca75006 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -179,26 +179,35 @@ static struct slice_mask *slice_mask_for_size(struct
mm_struct *mm, int psize)
#error "Must define the slice masks for page sizes supported by the platform"
#endif
-static int slice_check_fit(struct mm_struct *mm,
- const struct slice_mask *mask,
- const struct slice_mask *available)
+static bool slice_check_range_fits(struct mm_struct *mm,
+ const struct slice_mask *available,
+ unsigned long start, unsigned long len)
{
- DECLARE_BITMAP(result, SLICE_NUM_HIGH);
- /*
- * Make sure we just do bit compare only to the max
- * addr limit and not the full bit map size.
- */
- unsigned long slice_count =
GET_HIGH_SLICE_INDEX(mm->context.slb_addr_limit);
+ unsigned long end = start + len - 1;
+ u64 low_slices = 0;
- if (!SLICE_NUM_HIGH)
- return (mask->low_slices & available->low_slices) ==
- mask->low_slices;
+ if (start < SLICE_LOW_TOP) {
+ unsigned long mend = min(end, (SLICE_LOW_TOP - 1));
See slice_range_to_mask()
You'll have an issue here with PPC32, you have to cast (SLICE_LOW_TOP -
1) to unsigned long because SLICE_LOW_TOP is unsigned long long on PPC32
+
+ low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1))
+ - (1u << GET_LOW_SLICE_INDEX(start));
+ }
+ if ((low_slices & available->low_slices) != low_slices)
+ return false;
+
+ if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
+ unsigned long start_index = GET_HIGH_SLICE_INDEX(start);
+ unsigned long align_end = ALIGN(end, (1UL << SLICE_HIGH_SHIFT));
+ unsigned long count = GET_HIGH_SLICE_INDEX(align_end) -
start_index;
+ unsigned long i;
- bitmap_and(result, mask->high_slices,
- available->high_slices, slice_count);
+ for (i = start_index; i < start_index + count; i++) {
+ if (!test_bit(i, available->high_slices))
+ return false;
+ }
What about using bitmap_find_next_zero_area()
+ }
- return (mask->low_slices & available->low_slices) == mask->low_slices &&
- bitmap_equal(result, mask->high_slices, slice_count);
+ return true;
}
static void slice_flush_segments(void *parm)
@@ -562,15 +571,11 @@ unsigned long slice_get_unmapped_area(unsigned long addr,
unsigned long len,
#endif
/* First check hint if it's valid or if we have MAP_FIXED */
- if (addr != 0 || fixed) {
- /* Build a mask for the requested range */
- slice_range_to_mask(addr, len, &mask);
- slice_print_mask(" mask", &mask);
-
+ if (addr || fixed) {
It is cleanup, should it really be part of this patch ?
/* Check if we fit in the good mask. If we do, we just return,
* nothing else to do
*/
- if (slice_check_fit(mm, &mask, &good_mask)) {
+ if (slice_check_range_fits(mm, &good_mask, addr, len)) {
slice_dbg(" fits good !\n");
return addr;
}
@@ -596,10 +601,11 @@ unsigned long slice_get_unmapped_area(unsigned long addr,
unsigned long len,
slice_or_mask(&potential_mask, &good_mask);
slice_print_mask(" potential", &potential_mask);
- if ((addr != 0 || fixed) &&
- slice_check_fit(mm, &mask, &potential_mask)) {
- slice_dbg(" fits potential !\n");
- goto convert;
+ if (addr || fixed) {
+ if (slice_check_range_fits(mm, &potential_mask, addr, len)) {
+ slice_dbg(" fits potential !\n");
+ goto convert;
+ }
Why not keep the original structure and just replacing slice_check_fit()
by slice_check_range_fits() ?
I believe cleanups should not be mixed with real feature changes. If
needed, you should have a cleanup patch up front the serie.
Christophe
}
/* If we have MAP_FIXED and failed the above steps, then error out */
@@ -772,13 +778,12 @@ void slice_set_range_psize(struct mm_struct *mm, unsigned
long start,
int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,
unsigned long len)
{
- struct slice_mask mask, available;
+ struct slice_mask available;
unsigned int psize = mm->context.user_psize;
if (radix_enabled())
return 0;
- slice_range_to_mask(addr, len, &mask);
available = *slice_mask_for_size(mm, psize);
#ifdef CONFIG_PPC_64K_PAGES
/* We need to account for 4k slices too */
@@ -795,6 +800,6 @@ int is_hugepage_only_range(struct mm_struct *mm, unsigned
long addr,
slice_print_mask(" mask", &mask);
slice_print_mask(" available", &available);
#endif
- return !slice_check_fit(mm, &mask, &available);
+ return !slice_check_range_fits(mm, &available, addr, len);
}
#endif
