[dpdk-dev] mk: using initial-exec model for thread local variable

  When building share library, thread-local storage model will be changed
to global-dynamic. It will cost additional protect for read thread local
variable. By now only lcore id is this kind of varaible and not need to
dynamic share with other threads. So make TLS model back to initial-exec
like static library for better performance.

Signed-off-by: Marvin Liu <yong.liu@intel.com>
  

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Marvin Liu
> Sent: Saturday, April 28, 2018 5:54 PM
> To: dev@dpdk.org
> Cc: Liu, Yong <yong.liu@intel.com>
> Subject: [dpdk-dev] [PATCH] mk: using initial-exec model for thread local
> variable
> 
> When building share library, thread-local storage model will be changed to
> global-dynamic. It will cost additional protect for read thread local variable. By
> now only lcore id is this kind of varaible and not need to dynamic share with
> other threads. So make TLS model back to initial-exec like static library for
> better performance.
> 
> Signed-off-by: Marvin Liu <yong.liu@intel.com>
> 

For vhost-user, 
If no this pach, vhost user in shared lib perf drops 14.3% than working in static.
after applying the patch , vhost-user in shared lib can achieve the similar perf as  in static lib.

Tested-by:  Zhiyong Yang <zhiyong.yang@intel.com>
  

28/04/2018 06:39, Yang, Zhiyong:
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Marvin Liu
> Sent: Saturday, April 28, 2018 5:54 PM
> > 
> > When building share library, thread-local storage model will be changed to
> > global-dynamic. It will cost additional protect for read thread local variable. By
> > now only lcore id is this kind of varaible and not need to dynamic share with
> > other threads. So make TLS model back to initial-exec like static library for
> > better performance.
> > 
> > Signed-off-by: Marvin Liu <yong.liu@intel.com>
> > 
> 
> For vhost-user, 
> If no this pach, vhost user in shared lib perf drops 14.3% than working in static.
> after applying the patch , vhost-user in shared lib can achieve the similar perf as  in static lib.
> 
> Tested-by:  Zhiyong Yang <zhiyong.yang@intel.com>

For the record, I have decided to not try this optimization
in the last weeks of the 18.05 release.
However we could try it in 18.08 by applying the patch early in the cycle.
Is there anyone against this patch?