Re: [RFC] kbuild: bpf: Do not run pahole with -j on 32bit userspace

[Jiri Slaby <jirislaby@kernel.org>]

On 20. 08. 24, 10:59, Jiri Slaby (SUSE) wrote:
> From: Jiri Slaby <jslaby@suse.cz>
> 
> == WARNING ==
> This is only a PoC. There are deficiencies like CROSS_COMPILE or LLVM
> are completely unhandled.
> 
> The simple version is just do there:
>    ifeq ($(CONFIG_64BIT,y)
> but it has its own deficiencies, of course.
> 
> So any ideas, inputs?

Also as Shung-Hsi Yu suggests, we can cap -j to 1 in pahole proper when 
sizeof(long) == 4.

> == WARNING ==
> 
> When pahole is run with -j on 32bit userspace (32bit pahole in
> particular), it randomly fails with OOM:
>> btf_encoder__tag_kfuncs: Failed to get ELF section(62) data: out of memory.
>> btf_encoder__encode: failed to tag kfuncs!
> 
> or simply SIGSEGV (failed to allocate the btf encoder).
> 
> It very depends on how many threads are created.

I forgot to add, that it depends on the kernel version too. It happens 
much often with 6.11-rc now (vmlinux got big enough, apparently).

thanks,
-- 
js
suse labs