On 01/04/2013 11:01 PM, Tejun Heo wrote:
> On Fri, Jan 04, 2013 at 05:24:53PM +0800, Lin Feng wrote:
>> The memblock array is in ascending order and we traverse the memblock array in
>> reverse order so we can add some simple check to reduce the search work.
>>
>> Tejun fix a underflow bug in 5d53cb27d8, but I think we could break there for
>> the same reason.
>>
>> Cc: Tejun Heo <tj@xxxxxxxxxx>
>> Signed-off-by: Lin Feng <linfeng@xxxxxxxxxxxxxx>
>> ---
>> mm/memblock.c | 9 ++++++++-
>> 1 file changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/memblock.c b/mm/memblock.c
>> index 6259055..a710557 100644
>> --- a/mm/memblock.c
>> +++ b/mm/memblock.c
>> @@ -111,11 +111,18 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start,
>> end = max(start, end);
>>
>> for_each_free_mem_range_reverse(i, nid, &this_start, &this_end, NULL) {
>> + /*
>> + * exclude the regions out of the candidate range, since it's
>> + * likely to find a suitable range, we ignore the worst case.
>> + */
>> + if (this_start >= end)
>> + continue;
>> +
>> this_start = clamp(this_start, start, end);
>> this_end = clamp(this_end, start, end);
>>
>> if (this_end < size)
>> - continue;
>> + break;
>
> I don't know. This only saves looping when memblocks are below the
> requested size, right? I don't think it would matter in any way and
> would prefer to keep the logic as simple as possible.
Hi Tejun,
You're right, when we hit the 'if (this_end < size)' branch, it's nearly
the end of the whole search loops. I just got an impression that is
there any candidate range after we hit the if clause when I first read
this code, so... ;-)
thanks,
linfeng
>
> Thanks.
>
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