linux-kernel - Re: Re: [PATCH bpf-next v10 3/3] selftests/bpf: make usdt

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Message-ID: <aKLOuLGY93zYXbxA@krava>
Date: Mon, 18 Aug 2025 08:56:56 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: 赵佳炜 <phoenix500526@....com>
Cc: Jiri Olsa <olsajiri@...il.com>, ast@...nel.org, daniel@...earbox.net,
	andrii@...nel.org, yonghong.song@...ux.dev, bpf@...r.kernel.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH bpf-next v10 3/3] selftests/bpf: make usdt_o2
 reliably generate SIB USDT arg spec

On Sat, Aug 16, 2025 at 03:04:17PM +0800, 赵佳炜 wrote:
> 
> 
> 
> 
> 
> 
> Hi, Jiri. Sorry for my oversight, the optimized compile condition didn't work properly.
> 
> Could you try to replace the `__attribute__((optimize("O2")))` with `#pragma GCC optimize("O2")`
> in usdt_o2.c and verify it one more time?  I guess it'll help. In fact, the usdt1 argument spec generated 
> by the `__attribute__((optimize("O2")))` on my machine was `8@...x`, not `8@(%rdx,%rax,8)`.
> 
> For more detail:
> 
> > - #if defined(__GNUC__) && !defined(__clang__)
> > - __attribute__((optimize("O2")))
> >
> > +#if (defined(__GNUC__) && !defined(__clang__))
> > +#pragma GCC optimize("O2")
> > +#else
> > +#pragma message("non-gcc compiler: the correct probes might not be installed")
> > +#endif
> 
> Thanks

yep, that helped

  stapsdt              0x00000033       NT_STAPSDT (SystemTap probe descriptors)
    Provider: test
    Name: usdt1
    Location: 0x00000000007674d9, Base: 0x00000000035bc698, Semaphore: 0x0000000000000000
    Arguments: 8@(%rdx,%rax,8)


thanks,
jirka