2022-10-25 07:54:32

by Yajun Deng

Subject: [PATCH v2] memblock: don't run loop in memblock_add_range() twice

There is no need round twice in memblock_add_range().

We can call memblock_double_array() to extend the size if type->cnt
greater or equal to type->max before memblock_insert_region(); otherwise,
we can insert the new region directly.

v2:
- Add a comment when the allocation is required.

Signed-off-by: Yajun Deng <[email protected]>
---
mm/memblock.c | 69 ++++++++++++++++++---------------------------------
1 file changed, 24 insertions(+), 45 deletions(-)

diff --git a/mm/memblock.c b/mm/memblock.c
index 511d4783dcf1..602fa8ee9b71 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -578,10 +578,10 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
phys_addr_t base, phys_addr_t size,
int nid, enum memblock_flags flags)
{
- bool insert = false;
phys_addr_t obase = base;
phys_addr_t end = base + memblock_cap_size(base, &size);
- int idx, nr_new;
+ unsigned long ocnt = type->cnt;
+ int idx;
struct memblock_region *rgn;

if (!size)
@@ -598,25 +598,6 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
return 0;
}

- /*
- * The worst case is when new range overlaps all existing regions,
- * then we'll need type->cnt + 1 empty regions in @type. So if
- * type->cnt * 2 + 1 is less than type->max, we know
- * that there is enough empty regions in @type, and we can insert
- * regions directly.
- */
- if (type->cnt * 2 + 1 < type->max)
- insert = true;
-
-repeat:
- /*
- * The following is executed twice. Once with %false @insert and
- * then with %true. The first counts the number of regions needed
- * to accommodate the new area. The second actually inserts them.
- */
- base = obase;
- nr_new = 0;
-
for_each_memblock_type(idx, type, rgn) {
phys_addr_t rbase = rgn->base;
phys_addr_t rend = rbase + rgn->size;
@@ -634,11 +615,18 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,
WARN_ON(nid != memblock_get_region_node(rgn));
#endif
WARN_ON(flags != rgn->flags);
- nr_new++;
- if (insert)
- memblock_insert_region(type, idx++, base,
- rbase - base, nid,
- flags);
+
+ /*
+ * if type->cnt greater or equal to type->max,
+ * resize array; otherwise, insert directly.
+ */
+ if ((type->cnt >= type->max) &&
+ memblock_double_array(type, obase, size))
+ return -ENOMEM;
+
+ memblock_insert_region(type, idx++, base,
+ rbase - base, nid,
+ flags);
}
/* area below @rend is dealt with, forget about it */
base = min(rend, end);
@@ -646,29 +634,20 @@ static int __init_memblock memblock_add_range(struct memblock_type *type,

/* insert the remaining portion */
if (base < end) {
- nr_new++;
- if (insert)
- memblock_insert_region(type, idx, base, end - base,
- nid, flags);
+ if ((type->cnt >= type->max) &&
+ memblock_double_array(type, obase, size))
+ return -ENOMEM;
+
+ memblock_insert_region(type, idx, base, end - base,
+ nid, flags);
}

- if (!nr_new)
+ if (ocnt == type->cnt)
return 0;

- /*
- * If this was the first round, resize array and repeat for actual
- * insertions; otherwise, merge and return.
- */
- if (!insert) {
- while (type->cnt + nr_new > type->max)
- if (memblock_double_array(type, obase, size) < 0)
- return -ENOMEM;
- insert = true;
- goto repeat;
- } else {
- memblock_merge_regions(type);
- return 0;
- }
+ memblock_merge_regions(type);
+
+ return 0;
}

/**
--
2.25.1

2022-10-31 08:34:12

by Mike Rapoport

Subject: Re: [PATCH v2] memblock: don't run loop in memblock_add_range() twice

On Tue, Oct 25, 2022 at 03:09:43PM +0800, Yajun Deng wrote:
> There is no need round twice in memblock_add_range().
>
> We can call memblock_double_array() to extend the size if type->cnt
> greater or equal to type->max before memblock_insert_region(); otherwise,
> we can insert the new region directly.
>
> v2:
> - Add a comment when the allocation is required.
>
> Signed-off-by: Yajun Deng <[email protected]>
> ---
> mm/memblock.c | 69 ++++++++++++++++++---------------------------------
> 1 file changed, 24 insertions(+), 45 deletions(-)

Applied, thanks!