Re: [yocto] [poky] [PATCH] local.conf.sample: disable prelink

["Khem Raj" <raj.khem@gmail.com>]

On 6/15/21 8:21 AM, Alexander Kanavin wrote:
> 
> 
> On Tue, 15 Jun 2021 at 10:55, Alexander Kanavin <alex.kanavin@gmail.com 
> <mailto:alex.kanavin@gmail.com>> wrote:
> 
>     On Tue, 15 Jun 2021 at 10:48, Richard Purdie
>     <richard.purdie@linuxfoundation.org
>     <mailto:richard.purdie@linuxfoundation.org>> wrote:
> 
>         I appreciate the desire simply to delete/disable anything that
>         causes issues
>         but in this case I draw the line and my answer is no. It works
>         fine in the
>         vast majority of usage.
> 
> 
>     But where are the benchmarks that show it's actually beneficial? And
>     commitment from someone to maintain it and address open issues
>     (there are more than just this one)?
> 
> 
> I went ahead and ran some quick benchmarks myself. Specifically:
> 
> 1. Running 'free' after things have settled down at boot:
> 
> a) without prelink
> core-image-sato-sdk
>                 total        used        free      shared  buff/cache   
> available
> Mem:          489352      152104      236284         472      100964     
>   323824
> core-image-ptest-fast
>                total        used        free      shared  buff/cache   
> available
> Mem:        1004680       43456      927688         256       33536     
>   941156
> 
> b) with prelink
> core-image-sato-sdk
>                 total        used        free      shared  buff/cache   
> available
> Mem:          489352      153048      235544         468      100760     
>   322900
> core-image-ptest-fast
>                total        used        free      shared  buff/cache   
> available
> Mem:        1004680       44444      928128         256       32108     
>   940168
> 
> 2. Running -c testimage
> 
> a) without prelink
> core-image-sato-sdk () - Ran 66 tests in 96.693s
> core-image-sato-sdk () - Ran 66 tests in 96.469s
> core-image-sato-sdk () - Ran 66 tests in 94.994s
> core-image-ptest-fast () - Ran 66 tests in 583.767s
> core-image-ptest-fast () - Ran 66 tests in 576.564s
> core-image-ptest-fast () - Ran 66 tests in 576.797s
> 
> b) with prelink
> core-image-sato-sdk () - Ran 66 tests in 96.390s
> core-image-sato-sdk () - Ran 66 tests in 96.615s
> core-image-sato-sdk () - Ran 66 tests in 95.596s
> core-image-ptest-fast () - Ran 66 tests in 576.248s
> core-image-ptest-fast () - Ran 66 tests in 574.618s
> core-image-ptest-fast () - Ran 66 tests in 576.760s
>

I think the advantage is not on high end CPUs but more on less powerful 
ones, so perhaps trying it on something like rpi0 or lower would be good


> So the memory usage is actually *better* without prelink. And any timing 
> benefits are lost in statistical noise, in these tests at least.
> 
> So I do not think it is wrong to question the usefulness of this 
> feature. I'd like to hear Mark's take on this, as prelink-cross is 
> primarily his work, he's put a lot of effort into it, and I would want 
> to know where the benefits are. Note that Red Hat abandoned prelink in 
> 2013, and prelink-cross likewise hasn't seen any commits for two years.
> 



> Alex
> 
> 
> 
>