Performance - linking against DPDK shared vs static libraries

Performance - linking against DPDK shared vs static libraries

[Kavanagh, Mark B]

Hi,

I build a switching application, which links against DPDK shared libraries; when I run the application, I see throughput of X.  I then build the application again, except this time I link against DPDK shared libraries, having modified the application's build parameters appropriately.  In this case, I see a performance drop of around .04%, which given the high throughput of the application is significant.

Is such performance degradation to be expected when using DPDK shared libraries, and if not, are there any best-known methods for preventing performance degradation, assuming that I may be constrained to using shared libraries going forward?

Thanks,
Mark
--------------------------------------------------------------
Intel Shannon Limited
Registered in Ireland
Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
Registered Number: 308263
Business address: Dromore House, East Park, Shannon, Co. Clare

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Re: Performance - linking against DPDK shared vs static libraries

[Antti Kantee]

On 23/07/14 15:58, Kavanagh, Mark B wrote:
> Hi,
>
> I build a switching application, which links against DPDK shared libraries; when I run the application, I see throughput of X.  I then build the application again, except this time I link against DPDK shared libraries, having modified the application's build parameters appropriately.  In this case, I see a performance drop of around .04%, which given the high throughput of the application is significant.
>
> Is such performance degradation to be expected when using DPDK shared libraries, and if not, are there any best-known methods for preventing performance degradation, assuming that I may be constrained to using shared libraries going forward?

Do you mean .04% or 4%?  I would be more inclined to believe the latter. 
  Shared libraries are inherently slower due to indirection from PIC, 
and being required to use them seems like a silly constraint in the 
context of high-performance computing.

   - antti

Re: Performance - linking against DPDK shared vs static libraries

[Kavanagh, Mark B]

-----Original Message-----
From: Antti Kantee [mailto:pooka-jIVgJlTk8bs@public.gmane.org] 
Sent: Wednesday, July 23, 2014 5:37 PM
To: Kavanagh, Mark B; dev-VfR2kkLFssw@public.gmane.org
Subject: Re: [dpdk-dev] Performance - linking against DPDK shared vs static libraries

On 23/07/14 15:58, Kavanagh, Mark B wrote:
>> Hi,
>>
>> I build a switching application, which links against DPDK shared libraries; when I run the application, I see throughput of X.  I then build the application again, except this time I link against DPDK shared libraries, having modified the application's build parameters appropriately.  In this case, I see a performance drop of around .04%, which given the high throughput of the application is significant.
>>
>> Is such performance degradation to be expected when using DPDK shared libraries, and if not, are there any best-known methods for preventing performance degradation, assuming that I may be constrained to using shared libraries going forward?

>Do you mean .04% or 4%?  I would be more inclined to believe the latter. 
>Shared libraries are inherently slower due to indirection from PIC, and being required to use them seems like a silly constraint in the context of high-performance computing.
 > - antti

It's actually the former, and I agree with your assertion regarding the constraint! 
I take it from your response then that the performance drop when using shared libraries is expected behavior?
--------------------------------------------------------------
Intel Shannon Limited
Registered in Ireland
Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
Registered Number: 308263
Business address: Dromore House, East Park, Shannon, Co. Clare

This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.

Re: Performance - linking against DPDK shared vs static libraries

[Matthew Hall]

On Wed, Jul 23, 2014 at 09:43:49PM +0000, Kavanagh, Mark B wrote:
> I take it ... that the performance drop when using shared libraries is 
> expected behavior?

s/expected behavior/and unavoidable consequence/g

;)

Matthew Hall.

Re: Performance - linking against DPDK shared vs static libraries

[Kavanagh, Mark B]

Many thanks to all for your help.

-----Original Message-----
From: Matthew Hall [mailto:mhall-Hv3ogNYU3JfZZajBQzqCxQ@public.gmane.org] 
Sent: Wednesday, July 23, 2014 10:56 PM
To: Kavanagh, Mark B
Cc: Antti Kantee; dev-VfR2kkLFssw@public.gmane.org
Subject: Re: [dpdk-dev] Performance - linking against DPDK shared vs static libraries

On Wed, Jul 23, 2014 at 09:43:49PM +0000, Kavanagh, Mark B wrote:
> I take it ... that the performance drop when using shared libraries is 
> expected behavior?

s/expected behavior/and unavoidable consequence/g

;)

Matthew Hall.
--------------------------------------------------------------
Intel Shannon Limited
Registered in Ireland
Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
Registered Number: 308263
Business address: Dromore House, East Park, Shannon, Co. Clare

This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.

Re: Performance - linking against DPDK shared vs static libraries

[Stephen Hemminger]

On Wed, 23 Jul 2014 15:58:06 +0000
"Kavanagh, Mark B" <mark.b.kavanagh-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> wrote:

> Hi,
> 
> I build a switching application, which links against DPDK shared libraries; when I run the application, I see throughput of X.  I then build the application again, except this time I link against DPDK shared libraries, having modified the application's build parameters appropriately.  In this case, I see a performance drop of around .04%, which given the high throughput of the application is significant.
> 
> Is such performance degradation to be expected when using DPDK shared libraries, and if not, are there any best-known methods for preventing performance degradation, assuming that I may be constrained to using shared libraries going forward?
> 
> Thanks,
> Mark
> --------------------------------------------------------------
> Intel Shannon Limited
> Registered in Ireland
> Registered Office: Collinstown Industrial Park, Leixlip, County Kildare
> Registered Number: 308263
> Business address: Dromore House, East Park, Shannon, Co. Clare
> 
> This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.
> 

Shared libraries live on different pages and cause more TLB misses.