Re: [yocto] Limiting Yocto Memory Usage

Hi,

Op 14-07-2026 om 23:33 schreef Randy MacLeod:
> Hi Luis,
> 
> On 2026-07-10 17:26, Luis Merayo via lists.yoctoproject.org wrote:
>> Hi,
>>
>> I would like to know if there is a way to limit Bitbake's Memory usage 
>> to a specific percentage of the available RAM. For example, can the 
>> Yocto build be limited to use a maximum of 70% of RAM?
> Not without using a container to do the build.
>>
>> Could these three variables achieve this?
>>
>> BB_PRESSURE_MAX_CPU <https://docs.yoctoproject.org/dev/ref-manual/ 
>> variables.html#term-BB_PRESSURE_MAX_CPU>, BB_PRESSURE_MAX_IO <https:// 
>> docs.yoctoproject.org/dev/ref-manual/variables.html#term- 
>> BB_PRESSURE_MAX_IO> , BB_PRESSURE_MAX_MEMORY <https:// 
>> docs.yoctoproject.org/dev/ref-manual/variables.html#term- 
>> BB_PRESSURE_MAX_MEMORY>
>>
>> I see the range for these variables is from 1 to 1000000, so I would 
>> like to understand if there is a way to specify their values as a 
>> function of the available RAM.
> No, there is only pressure when resources are over-commited so if you 
> have free memory, there's no over-commit.
> https://docs.kernel.org/accounting/psi.html
> 
> That's the design intent of the bitbake PRESSURE regulation system.
> 
> There are plans to work on additional build system regulation.
> 
> The first idea is to use the jobserver design:
> https://lore.kernel.org/openembedded-core/?q=GNU+AND+jobserver+ 
> +AND+f%3Amacleod
> and that would indirectly limit memory consumption since there would be 
> fewer instances of gcc / rustc / ... running
> at once.

I do that, since 2 years or so. 
https://github.com/htot/meta-intel-edison/commits/whinlatter/

In principle you need to catch the call to make and ninja (to force them 
to use the jobserver) and patch bitbake (see setup.sh) to act as a 
jobserver.

Now got it working on wrynose, still need to push that. Maybe later 
today.With wrynose ninja has support for jobserver so doesn't need 
patching, just a bbappend.

With this you can limit the number of compile jobs. On my builds I found 
g++ compiles are the heaviest, about 1GB RAM each. So, with 16 cores I 
need 16 GB.
Separately I found linking nodejs takes 5 x 5GB (5 jobs linking with 
LTO?). So, I limited that to just one (since both nodejs and 
nodejs-native can be built at the same time).

I'm not building rust so there may be other bottlenecks to resolve.

> There's also an even less clear idea about being able to restrict the 
> build by specifying memory usage.
> That shouldn't be too hard to implement in bitbake in the same point 
> where the pressure checks happen.
> Are you interested in working on that ?
> 
> There are of course other levers to pull to reduce CPU/memory consumption:
> https://docs.yoctoproject.org/dev-manual/limiting-resources.html
> 
> Have you tried them ?
> 
> 
>>
>> Regards,
>>
>> Luis
>>
>>
>>
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> -- 
> # Randy MacLeod
> # Wind River Linux
>