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


Alexander Kanavin
 



On Tue, 15 Jun 2021 at 10:55, Alexander Kanavin <alex.kanavin@...> wrote:
On Tue, 15 Jun 2021 at 10:48, Richard Purdie <richard.purdie@...> 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

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

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