linux-kernel - Re: [PATCH v1 3/7] tools: Partial import of prefetch.h

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Message-ID: <aIr2-7842FIi2_8V@google.com>
Date: Wed, 30 Jul 2025 21:54:19 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Yuzhuo Jing <yuzhuo@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Liang Kan <kan.liang@...ux.intel.com>, Yuzhuo Jing <yzj@...ch.edu>,
	Andrea Parri <parri.andrea@...il.com>,
	Palmer Dabbelt <palmer@...osinc.com>,
	Charlie Jenkins <charlie@...osinc.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Kumar Kartikeya Dwivedi <memxor@...il.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Barret Rhoden <brho@...gle.com>,
	Alexandre Ghiti <alexghiti@...osinc.com>,
	Guo Ren <guoren@...nel.org>, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH v1 3/7] tools: Partial import of prefetch.h

On Mon, Jul 28, 2025 at 07:26:36PM -0700, Yuzhuo Jing wrote:
> Import only prefetch and prefetchw but not page and range related
> methods.
> 
> Signed-off-by: Yuzhuo Jing <yuzhuo@...gle.com>
> ---
>  tools/include/linux/prefetch.h | 41 ++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
>  create mode 100644 tools/include/linux/prefetch.h
> 
> diff --git a/tools/include/linux/prefetch.h b/tools/include/linux/prefetch.h
> new file mode 100644
> index 000000000000..1ed8678f4824
> --- /dev/null
> +++ b/tools/include/linux/prefetch.h
> @@ -0,0 +1,41 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + *  Generic cache management functions. Everything is arch-specific,  
> + *  but this header exists to make sure the defines/functions can be
> + *  used in a generic way.
> + *
> + *  2000-11-13  Arjan van de Ven   <arjan@...rus.demon.nl>
> + *
> + */
> +
> +#ifndef _LINUX_PREFETCH_H
> +#define _LINUX_PREFETCH_H
> +
> +/*
> +	prefetch(x) attempts to pre-emptively get the memory pointed to
> +	by address "x" into the CPU L1 cache. 
> +	prefetch(x) should not cause any kind of exception, prefetch(0) is
> +	specifically ok.
> +
> +	prefetch() should be defined by the architecture, if not, the 
> +	#define below provides a no-op define.	
> +	
> +	There are 2 prefetch() macros:
> +	
> +	prefetch(x)  	- prefetches the cacheline at "x" for read
> +	prefetchw(x)	- prefetches the cacheline at "x" for write
> +	
> +	there is also PREFETCH_STRIDE which is the architecure-preferred 
> +	"lookahead" size for prefetching streamed operations.
> +	
> +*/
> +
> +#ifndef ARCH_HAS_PREFETCH
> +#define prefetch(x) __builtin_prefetch(x)
> +#endif

Do we have ARCH_HAS_PREFETCH somewhere?

Thanks,
Namhyung

> +
> +#ifndef ARCH_HAS_PREFETCHW
> +#define prefetchw(x) __builtin_prefetch(x,1)
> +#endif
> +
> +#endif
> -- 
> 2.50.1.487.gc89ff58d15-goog
>