[dpdk-dev] [PATCH 1/8] lpm: Fix pointer aliasing issues
Aaron Conole
aconole at redhat.com
Thu Feb 25 23:00:13 CET 2016
Hi Bruce,
Bruce Richardson <bruce.richardson at intel.com> writes:
> On Thu, Feb 25, 2016 at 01:48:34PM -0500, Aaron Conole wrote:
>> The current implementation attempts to use a uint16_t to alias the lpm table
>> structures. Such aliasing can break optimizer performance. This patch uses
>> union type indirection and adds static inline functions for performing the
>> aliasing.
>>
>> Signed-off-by: Aaron Conole <aconole at redhat.com>
>> ---
>> lib/librte_lpm/rte_lpm.h | 53 +++++++++++++++++++++++++++++++++++++-----------
>> 1 file changed, 41 insertions(+), 12 deletions(-)
>>
>> diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h
>> index c299ce2..eae6ff1 100644
>> --- a/lib/librte_lpm/rte_lpm.h
>> +++ b/lib/librte_lpm/rte_lpm.h
>> @@ -157,6 +157,33 @@ struct rte_lpm {
>> };
>>
>> /**
>> + * Convert from tbl_entry types to integer types
>> + */
>> +static inline uint16_t
>> +rte_lpm_tbl24_entry_to_uint16(const struct rte_lpm_tbl24_entry *entry)
>> +{
>> + union {
>> + uint16_t i;
>> + struct rte_lpm_tbl24_entry s;
>> + } tbl_entry_u;
>> +
>> + tbl_entry_u.s = *entry;
>> + return tbl_entry_u.i;
>> +}
>> +
>> +static inline uint16_t
>> +rte_lpm_tbl8_entry_to_uint16(const struct rte_lpm_tbl8_entry *entry)
>> +{
>> + union {
>> + uint16_t i;
>> + struct rte_lpm_tbl8_entry s;
>> + } tbl_entry_u;
>> +
>> + tbl_entry_u.s = *entry;
>> + return tbl_entry_u.i;
>> +}
>> +
>
> These two new functions could be reduced to one with the help of patch:
> http://dpdk.org/dev/patchwork/patch/9087/
>
> Anyone care to go back and review or ack that patch for me and simplify all
> the lpm code just that little bit?
I definitely ack that patch; I also want to apply it in my local testing
setup and test a bit so you can add my Tested-by, but it looks sane on
the surface.
Thanks so much for the review!
> /Bruce
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