Re: [PATCH 1/1] memblock cleanup: Remove unnecessary check in memblock_find_in_range_node()
On 08/15/2013 11:27 AM, Tejun Heo wrote: Hello, Tang. On Thu, Aug 15, 2013 at 11:23:19AM +0800, Tang Chen wrote: Furthermore, we don't need to check "if (this_end< size)" actually. Without this confusing check, we only waste some loops. So this patch removes the check. Signed-off-by: Tang Chen --- mm/memblock.c |3 --- 1 files changed, 0 insertions(+), 3 deletions(-) diff --git a/mm/memblock.c b/mm/memblock.c index a847bfe..e0c626e 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -114,9 +114,6 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start, this_start = clamp(this_start, start, end); this_end = clamp(this_end, start, end); - if (this_end< size) - continue; - cand = round_down(this_end - size, align); if (cand>= this_start) return cand; Hmmm... maybe I'm missing something but are you sure? "this_end - size" can underflow and "cand>= this_start" will be true incorrectly. Oh, you are right... Please ignore this. I didn't read it carefully. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 1/1] memblock cleanup: Remove unnecessary check in memblock_find_in_range_node()
Hello, Tang. On Thu, Aug 15, 2013 at 11:23:19AM +0800, Tang Chen wrote: > Furthermore, we don't need to check "if (this_end < size)" actually. Without > this confusing check, we only waste some loops. So this patch removes the > check. > > Signed-off-by: Tang Chen > --- > mm/memblock.c |3 --- > 1 files changed, 0 insertions(+), 3 deletions(-) > > diff --git a/mm/memblock.c b/mm/memblock.c > index a847bfe..e0c626e 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > @@ -114,9 +114,6 @@ phys_addr_t __init_memblock > memblock_find_in_range_node(phys_addr_t start, > this_start = clamp(this_start, start, end); > this_end = clamp(this_end, start, end); > > - if (this_end < size) > - continue; > - > cand = round_down(this_end - size, align); > if (cand >= this_start) > return cand; Hmmm... maybe I'm missing something but are you sure? "this_end - size" can underflow and "cand >= this_start" will be true incorrectly. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 1/1] memblock cleanup: Remove unnecessary check in memblock_find_in_range_node()
In memblock_find_in_range_node(), it has the following check at line 117 and
118:
113 for_each_free_mem_range_reverse(i, nid, &this_start, &this_end,
NULL) {
114 this_start = clamp(this_start, start, end);
115 this_end = clamp(this_end, start, end);
116
117 if (this_end < size)
118 continue;
119
120 cand = round_down(this_end - size, align);
121 if (cand >= this_start)
122 return cand;
123 }
Since it finds memory from higher memory downwards, if this_end < size,
we can break because the rest memory will all under size. It won't satisfy
us ang more.
Furthermore, we don't need to check "if (this_end < size)" actually. Without
this confusing check, we only waste some loops. So this patch removes the
check.
Signed-off-by: Tang Chen
---
mm/memblock.c |3 ---
1 files changed, 0 insertions(+), 3 deletions(-)
diff --git a/mm/memblock.c b/mm/memblock.c
index a847bfe..e0c626e 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -114,9 +114,6 @@ phys_addr_t __init_memblock
memblock_find_in_range_node(phys_addr_t start,
this_start = clamp(this_start, start, end);
this_end = clamp(this_end, start, end);
- if (this_end < size)
- continue;
-
cand = round_down(this_end - size, align);
if (cand >= this_start)
return cand;
--
1.7.1
--
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