[dpdk-dev] [PATCH, v2] mempool: avoid memory waste with large pagesize

[dpdk-dev] [PATCH, v2] mempool: avoid memory waste with large pagesize

[Stephen Hemminger]

If page size is large (like 64K on ARM) and object size is small
then don't waste lots of memory by rounding up to page size.
Instead, round up so that 1 or more objects all fit in a page.

This preserves the requirement that an object must not a page
or virt2phys would break, and makes sure 62K is not wasted per mbuf.

Also, fix invalid use of printf (versus log) for error reporting.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
v2 - fix trailer_size calculation, and replace printf with log

 lib/librte_mempool/rte_mempool.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
index f8781e1..ff08a1a 100644
--- a/lib/librte_mempool/rte_mempool.c
+++ b/lib/librte_mempool/rte_mempool.c
@@ -300,18 +300,23 @@ rte_mempool_calc_obj_size(uint32_t elt_size, uint32_t flags,
 	if (! rte_eal_has_hugepages()) {
 		/*
 		 * compute trailer size so that pool elements fit exactly in
-		 * a standard page
+		 * a standard page. If elements are smaller than a page
+		 * then allow multiple elements per page
 		 */
-		int page_size = getpagesize();
-		int new_size = page_size - sz->header_size - sz->elt_size;
-		if (new_size < 0 || (unsigned int)new_size < sz->trailer_size) {
-			printf("When hugepages are disabled, pool objects "
-			       "can't exceed PAGE_SIZE: %d + %d + %d > %d\n",
-			       sz->header_size, sz->elt_size, sz->trailer_size,
-			       page_size);
+		unsigned new_size, orig_size, page_size;
+
+		page_size = getpagesize();
+		orig_size = sz->header_size + sz->elt_size;
+		new_size = rte_align32pow2(orig_size);
+		if (new_size > page_size) {
+			RTE_LOG(ERR, MEMPOOL,
+				"When hugepages are disabled, pool objects "
+				"can't exceed PAGE_SIZE: %u + %u + %u > %u\n",
+				sz->header_size, sz->elt_size, sz->trailer_size,
+				page_size);
 			return 0;
 		}
-		sz->trailer_size = new_size;
+		sz->trailer_size = new_size - orig_size;
 	}
 
 	/* this is the size of an object, including header and trailer */
-- 
2.1.4

Re: [dpdk-dev] [PATCH, v2] mempool: avoid memory waste with large pagesize

[Olivier MATZ]

Hello,

On 03/09/2016 10:12 PM, Stephen Hemminger wrote:
> If page size is large (like 64K on ARM) and object size is small
> then don't waste lots of memory by rounding up to page size.
> Instead, round up so that 1 or more objects all fit in a page.
> 
> This preserves the requirement that an object must not a page
> or virt2phys would break, and makes sure 62K is not wasted per mbuf.
> 
> Also, fix invalid use of printf (versus log) for error reporting.
> 
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
> v2 - fix trailer_size calculation, and replace printf with log
> 
>  lib/librte_mempool/rte_mempool.c | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
> index f8781e1..ff08a1a 100644
> --- a/lib/librte_mempool/rte_mempool.c
> +++ b/lib/librte_mempool/rte_mempool.c
> @@ -300,18 +300,23 @@ rte_mempool_calc_obj_size(uint32_t elt_size, uint32_t flags,
>  	if (! rte_eal_has_hugepages()) {
>  		/*
>  		 * compute trailer size so that pool elements fit exactly in
> -		 * a standard page
> +		 * a standard page. If elements are smaller than a page
> +		 * then allow multiple elements per page
>  		 */
> -		int page_size = getpagesize();
> -		int new_size = page_size - sz->header_size - sz->elt_size;
> -		if (new_size < 0 || (unsigned int)new_size < sz->trailer_size) {
> -			printf("When hugepages are disabled, pool objects "
> -			       "can't exceed PAGE_SIZE: %d + %d + %d > %d\n",
> -			       sz->header_size, sz->elt_size, sz->trailer_size,
> -			       page_size);
> +		unsigned new_size, orig_size, page_size;
> +
> +		page_size = getpagesize();
> +		orig_size = sz->header_size + sz->elt_size;
> +		new_size = rte_align32pow2(orig_size);
> +		if (new_size > page_size) {
> +			RTE_LOG(ERR, MEMPOOL,
> +				"When hugepages are disabled, pool objects "
> +				"can't exceed PAGE_SIZE: %u + %u + %u > %u\n",
> +				sz->header_size, sz->elt_size, sz->trailer_size,
> +				page_size);
>  			return 0;
>  		}
> -		sz->trailer_size = new_size;
> +		sz->trailer_size = new_size - orig_size;
>  	}
>  
>  	/* this is the size of an object, including header and trailer */
> 

It still does not work. When CONFIG_RTE_LIBRTE_MEMPOOL_DEBUG=y:

mp = rte_mempool_create("test", 128,
	64, 0, 0, NULL, NULL, NULL, NULL, SOCKET_ID_ANY, 0);
rte_mempool_dump(stdout, mp);

  populated_size=128
  header_size=64
  elt_size=64
  trailer_size=64
  total_obj_size=192


Regards,
Olivier

Re: [dpdk-dev] [PATCH, v2] mempool: avoid memory waste with large pagesize

[Ferruh Yigit]

On 3/10/2016 8:37 AM, Olivier MATZ wrote:
> Hello,
> 
> On 03/09/2016 10:12 PM, Stephen Hemminger wrote:
>> If page size is large (like 64K on ARM) and object size is small
>> then don't waste lots of memory by rounding up to page size.
>> Instead, round up so that 1 or more objects all fit in a page.
>>
>> This preserves the requirement that an object must not a page
>> or virt2phys would break, and makes sure 62K is not wasted per mbuf.
>>
>> Also, fix invalid use of printf (versus log) for error reporting.
>>
>> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
>> ---
>> v2 - fix trailer_size calculation, and replace printf with log
>>
>>  lib/librte_mempool/rte_mempool.c | 23 ++++++++++++++---------
>>  1 file changed, 14 insertions(+), 9 deletions(-)
>>
>> diff --git a/lib/librte_mempool/rte_mempool.c b/lib/librte_mempool/rte_mempool.c
>> index f8781e1..ff08a1a 100644
>> --- a/lib/librte_mempool/rte_mempool.c
>> +++ b/lib/librte_mempool/rte_mempool.c
>> @@ -300,18 +300,23 @@ rte_mempool_calc_obj_size(uint32_t elt_size, uint32_t flags,
>>  	if (! rte_eal_has_hugepages()) {
>>  		/*
>>  		 * compute trailer size so that pool elements fit exactly in
>> -		 * a standard page
>> +		 * a standard page. If elements are smaller than a page
>> +		 * then allow multiple elements per page
>>  		 */
>> -		int page_size = getpagesize();
>> -		int new_size = page_size - sz->header_size - sz->elt_size;
>> -		if (new_size < 0 || (unsigned int)new_size < sz->trailer_size) {
>> -			printf("When hugepages are disabled, pool objects "
>> -			       "can't exceed PAGE_SIZE: %d + %d + %d > %d\n",
>> -			       sz->header_size, sz->elt_size, sz->trailer_size,
>> -			       page_size);
>> +		unsigned new_size, orig_size, page_size;
>> +
>> +		page_size = getpagesize();
>> +		orig_size = sz->header_size + sz->elt_size;
>> +		new_size = rte_align32pow2(orig_size);
>> +		if (new_size > page_size) {
>> +			RTE_LOG(ERR, MEMPOOL,
>> +				"When hugepages are disabled, pool objects "
>> +				"can't exceed PAGE_SIZE: %u + %u + %u > %u\n",
>> +				sz->header_size, sz->elt_size, sz->trailer_size,
>> +				page_size);
>>  			return 0;
>>  		}
>> -		sz->trailer_size = new_size;
>> +		sz->trailer_size = new_size - orig_size;
>>  	}
>>  
>>  	/* this is the size of an object, including header and trailer */
>>
> 
> It still does not work. When CONFIG_RTE_LIBRTE_MEMPOOL_DEBUG=y:
> 
> mp = rte_mempool_create("test", 128,
> 	64, 0, 0, NULL, NULL, NULL, NULL, SOCKET_ID_ANY, 0);
> rte_mempool_dump(stdout, mp);
> 
>   populated_size=128
>   header_size=64
>   elt_size=64
>   trailer_size=64
>   total_obj_size=192
> 
With --no-huge (since patch updates that part), it gives:
  header_size=64
  elt_size=64
  trailer_size=0
  total_obj_size=128
  private_data_size=3904

1- private_data still rounds to page size, not sure if this is a problem.
2- with MEMPOOL_DEBUG=y, trailer_size is 0, comment in code says it
should keep cookie, not sure if this is a problem.

Regards,
ferruh

Re: [dpdk-dev] [PATCH, v2] mempool: avoid memory waste with large pagesize

[Olivier MATZ]

>> It still does not work. When CONFIG_RTE_LIBRTE_MEMPOOL_DEBUG=y:
>>
>> mp = rte_mempool_create("test", 128,
>> 	64, 0, 0, NULL, NULL, NULL, NULL, SOCKET_ID_ANY, 0);
>> rte_mempool_dump(stdout, mp);
>>
>>   populated_size=128
>>   header_size=64
>>   elt_size=64
>>   trailer_size=64
>>   total_obj_size=192
>>
> With --no-huge (since patch updates that part), it gives:
>   header_size=64
>   elt_size=64
>   trailer_size=0
>   total_obj_size=128
>   private_data_size=3904
> 
> 1- private_data still rounds to page size, not sure if this is a problem.
> 2- with MEMPOOL_DEBUG=y, trailer_size is 0, comment in code says it
> should keep cookie, not sure if this is a problem.

Yes the trailer should at least be 8 bytes to store the cookie.

Re: [dpdk-dev] [PATCH, v2] mempool: avoid memory waste with large pagesize

[Stephen Hemminger]

On Thu, 10 Mar 2016 12:12:12 +0100
Olivier MATZ <olivier.matz@6wind.com> wrote:

> >> It still does not work. When CONFIG_RTE_LIBRTE_MEMPOOL_DEBUG=y:
> >>
> >> mp = rte_mempool_create("test", 128,
> >> 	64, 0, 0, NULL, NULL, NULL, NULL, SOCKET_ID_ANY, 0);
> >> rte_mempool_dump(stdout, mp);
> >>
> >>   populated_size=128
> >>   header_size=64
> >>   elt_size=64
> >>   trailer_size=64
> >>   total_obj_size=192
> >>
> > With --no-huge (since patch updates that part), it gives:
> >   header_size=64
> >   elt_size=64
> >   trailer_size=0
> >   total_obj_size=128
> >   private_data_size=3904
> > 
> > 1- private_data still rounds to page size, not sure if this is a problem.
> > 2- with MEMPOOL_DEBUG=y, trailer_size is 0, comment in code says it
> > should keep cookie, not sure if this is a problem.
> 
> Yes the trailer should at least be 8 bytes to store the cookie.
> 

Ok, will fix. that.