[dpdk-dev] [PATCH] librte_lpm: use field access instead of type conversion.

[Xuelin Shi]

Hi,

Needs more consideration.

RTE_LPM_VALID_EXT_ENTRY_BITMASK is defined as 0x0030, also little endian 
assumed.
Seems like the struct bit field also need some position conversion.

I would like to send v2 patch to fix that.

Thanks,
Shi Xuelin

> -Original Message-
> From: Bruce Richardson [mailto:bruce.richardson at intel.com]
> Sent: Thursday, February 12, 2015 19:18
> To: Shi Xuelin-B29237
> Cc: thomas.monjalon at 6wind.com; dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] librte_lpm: use field access instead of
> type conversion.
> 
> On Wed, Feb 11, 2015 at 02:12:59PM +0800, xuelin.shi at freescale.com wrote:
> > From: Xuelin Shi 
> >
> > struct tbl_entry{
> > uint8_t next_hop;
> > uint8_t valid :1;
> > uint8_t valid_group :1;
> > uint8_t depth :6
> > }
> > uint16_t tbl = (uint16_t)tbl_entry;
> > next_hop = (uint8_t)tbl;
> >
> > next_hop cannot get the correct value of the field if the cpu arch is
> > BIG_ENDIAN.
> >
> > change it to field access.
> >
> > Signed-off-by: Xuelin Shi 
> > ---
> >  lib/librte_lpm/rte_lpm.h | 7 +--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h index
> > 586300b..1af150c 100644
> > --- a/lib/librte_lpm/rte_lpm.h
> > +++ b/lib/librte_lpm/rte_lpm.h
> > @@ -273,6 +273,7 @@ rte_lpm_lookup(struct rte_lpm *lpm, uint32_t ip,
> > uint8_t *next_hop)  {
> > unsigned tbl24_index = (ip >> 8);
> > uint16_t tbl_entry;
> > +   struct rte_lpm_tbl8_entry *entry;
> >
> > /* DEBUG: Check user input arguments. */
> > RTE_LPM_RETURN_IF_TRUE(((lpm == NULL) || (next_hop == NULL)),
> > -EINVAL); @@ -290,8 +291,10 @@ rte_lpm_lookup(struct rte_lpm *lpm,
> uint32_t ip, uint8_t *next_hop)
> > tbl_entry = *(const uint16_t *)>tbl8[tbl8_index];
> > }
> >
> > -   *next_hop = (uint8_t)tbl_entry;
> > -   return (tbl_entry & RTE_LPM_LOOKUP_SUCCESS) ? 0 : -ENOENT;
> > +   entry = (struct rte_lpm_tbl8_entry *)_entry;
> > +   *next_hop = entry->next_hop;
> > +
> > +   return (entry->valid) ? 0 : -ENOENT;
> >  }
> >
> >  /**
> > --
> > 1.9.1
> >
> I've run a quick test using "lpm_autotest" inside the test app, and on my
> (Intel) platform, this patch has a small (but none-the-less significant)
> performance regression. How about the below as an alternative fix?
> 
> /Bruce
> 
> diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h index
> 586300b..de6f1cb 100644
> --- a/lib/librte_lpm/rte_lpm.h
> +++ b/lib/librte_lpm/rte_lpm.h
> @@ -44,6 +44,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  #include 
>  #include 
> @@ -287,7 +288,8 @@ rte_lpm_lookup(struct rte_lpm *lpm, uint32_t ip,
> uint8_t *next_hop)
> unsigned tbl8_index = (uint8_t)ip +
> ((uint8_t)tbl_entry *
> RTE_LPM_TBL8_GROUP_NUM_ENTRIES);
> 
> -   tbl_entry = *(const uint16_t *)>tbl8[tbl8_index];
> +   tbl_entry = rte_cpu_to_le_16(
> +   *(const uint16_t
> + *)>tbl8[tbl8_index]);
> }
> 
> *next_hop = (uint8_t)tbl_entry;

[dpdk-dev] [PATCH] librte_lpm: use field access instead of type conversion.

[Bruce Richardson]

On Wed, Feb 11, 2015 at 02:12:59PM +0800, xuelin.shi at freescale.com wrote:
> From: Xuelin Shi 
> 
> struct tbl_entry{
> uint8_t next_hop;
> uint8_t valid :1;
> uint8_t valid_group :1;
> uint8_t depth :6
> }
> uint16_t tbl = (uint16_t)tbl_entry;
> next_hop = (uint8_t)tbl;
> 
> next_hop cannot get the correct value of the field
> if the cpu arch is BIG_ENDIAN.
> 
> change it to field access.
> 
> Signed-off-by: Xuelin Shi 
> ---
>  lib/librte_lpm/rte_lpm.h | 7 +--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h
> index 586300b..1af150c 100644
> --- a/lib/librte_lpm/rte_lpm.h
> +++ b/lib/librte_lpm/rte_lpm.h
> @@ -273,6 +273,7 @@ rte_lpm_lookup(struct rte_lpm *lpm, uint32_t ip, uint8_t 
> *next_hop)
>  {
>   unsigned tbl24_index = (ip >> 8);
>   uint16_t tbl_entry;
> + struct rte_lpm_tbl8_entry *entry;
>  
>   /* DEBUG: Check user input arguments. */
>   RTE_LPM_RETURN_IF_TRUE(((lpm == NULL) || (next_hop == NULL)), -EINVAL);
> @@ -290,8 +291,10 @@ rte_lpm_lookup(struct rte_lpm *lpm, uint32_t ip, uint8_t 
> *next_hop)
>   tbl_entry = *(const uint16_t *)>tbl8[tbl8_index];
>   }
>  
> - *next_hop = (uint8_t)tbl_entry;
> - return (tbl_entry & RTE_LPM_LOOKUP_SUCCESS) ? 0 : -ENOENT;
> + entry = (struct rte_lpm_tbl8_entry *)_entry;
> + *next_hop = entry->next_hop;
> +
> + return (entry->valid) ? 0 : -ENOENT;
>  }
>  
>  /**
> -- 
> 1.9.1
> 
I've run a quick test using "lpm_autotest" inside the test app, and on my 
(Intel)
platform, this patch has a small (but none-the-less significant) performance
regression. How about the below as an alternative fix?

/Bruce

diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h
index 586300b..de6f1cb 100644
--- a/lib/librte_lpm/rte_lpm.h
+++ b/lib/librte_lpm/rte_lpm.h
@@ -44,6 +44,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -287,7 +288,8 @@ rte_lpm_lookup(struct rte_lpm *lpm, uint32_t ip, uint8_t 
*next_hop)
unsigned tbl8_index = (uint8_t)ip +
((uint8_t)tbl_entry * 
RTE_LPM_TBL8_GROUP_NUM_ENTRIES);

-   tbl_entry = *(const uint16_t *)>tbl8[tbl8_index];
+   tbl_entry = rte_cpu_to_le_16(
+   *(const uint16_t *)>tbl8[tbl8_index]);
}

*next_hop = (uint8_t)tbl_entry;

[dpdk-dev] [PATCH] librte_lpm: use field access instead of type conversion.

[xuelin....@freescale.com]

From: Xuelin Shi 

struct tbl_entry{
uint8_t next_hop;
uint8_t valid :1;
uint8_t valid_group :1;
uint8_t depth :6
}
uint16_t tbl = (uint16_t)tbl_entry;
next_hop = (uint8_t)tbl;

next_hop cannot get the correct value of the field
if the cpu arch is BIG_ENDIAN.

change it to field access.

Signed-off-by: Xuelin Shi 
---
 lib/librte_lpm/rte_lpm.h | 7 +--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h
index 586300b..1af150c 100644
--- a/lib/librte_lpm/rte_lpm.h
+++ b/lib/librte_lpm/rte_lpm.h
@@ -273,6 +273,7 @@ rte_lpm_lookup(struct rte_lpm *lpm, uint32_t ip, uint8_t 
*next_hop)
 {
unsigned tbl24_index = (ip >> 8);
uint16_t tbl_entry;
+   struct rte_lpm_tbl8_entry *entry;

/* DEBUG: Check user input arguments. */
RTE_LPM_RETURN_IF_TRUE(((lpm == NULL) || (next_hop == NULL)), -EINVAL);
@@ -290,8 +291,10 @@ rte_lpm_lookup(struct rte_lpm *lpm, uint32_t ip, uint8_t 
*next_hop)
tbl_entry = *(const uint16_t *)>tbl8[tbl8_index];
}

-   *next_hop = (uint8_t)tbl_entry;
-   return (tbl_entry & RTE_LPM_LOOKUP_SUCCESS) ? 0 : -ENOENT;
+   entry = (struct rte_lpm_tbl8_entry *)_entry;
+   *next_hop = entry->next_hop;
+
+   return (entry->valid) ? 0 : -ENOENT;
 }

 /**
-- 
1.9.1