On 12/10/2014 6:41 PM, Richardson, Bruce wrote:
> On Wed, Dec 10, 2014 at 10:25:41AM +0800, Michael Qiu wrote:
>> When the first address is the compared address in the loop,
>> it will also do memory copy, which is meaningless,
>> worse more, when hugepg_tbl is mostly in order. This should
>> be a big deal in large hugepage memory systerm(like hunderd
>> or thousand GB).
> I actually doubt the time taken by this sorting is a significant part of the
> initialization time taken, even for hundreds of GBs of memory. Do you have
> any measurements to confirm this?
> [However, that's not to say that we can't merge in this patch]
I've no hardware env of so huge memory, so I haven't do measurements on
this.
This is not a big improvement, but indeed it may do lots of useless
memory copy in initialize stat.
It could, at least could save time :)
Thanks,
Michael
>
>
>> Meanwhile smallest_idx never be a value of -1,so remove this check.
>>
>> This patch also includes some coding style fix.
>>
>> Signed-off-by: Michael Qiu <michael.qiu at intel.com>
>> ---
>> lib/librte_eal/linuxapp/eal/eal_memory.c | 13 +++++--------
>> 1 file changed, 5 insertions(+), 8 deletions(-)
>>
>> diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c
>> b/lib/librte_eal/linuxapp/eal/eal_memory.c
>> index e6cb919..700aba2 100644
>> --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
>> +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
>> @@ -678,14 +678,13 @@ error:
>> static int
>> sort_by_physaddr(struct hugepage_file *hugepg_tbl, struct hugepage_info
>> *hpi)
>> {
>> - unsigned i, j;
>> - int compare_idx;
>> + unsigned i, j, compare_idx;
>> uint64_t compare_addr;
>> struct hugepage_file tmp;
>>
>> for (i = 0; i < hpi->num_pages[0]; i++) {
>> compare_addr = 0;
>> - compare_idx = -1;
>> + compare_idx = i;
>>
>> /*
>> * browse all entries starting at 'i', and find the
>> @@ -704,11 +703,9 @@ sort_by_physaddr(struct hugepage_file *hugepg_tbl,
>> struct hugepage_info *hpi)
>> }
>> }
>>
>> - /* should not happen */
>> - if (compare_idx == -1) {
>> - RTE_LOG(ERR, EAL, "%s(): error in physaddr sorting\n",
>> __func__);
>> - return -1;
>> - }
>> + /* avoid memory copy when the first entry is the compared */
>> + if (compare_idx == i)
>> + continue;
>>
>> /* swap the 2 entries in the table */
>> memcpy(&tmp, &hugepg_tbl[compare_idx],
>> --
>> 1.9.3
>>
