linux-kernel - Re: [PATCH RFC 3/4] mm, slab: add static key for should

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Message-ID: <Zlpg0OFOsOSxrh9I@P9FQF9L96D.corp.robot.car>
Date: Fri, 31 May 2024 16:44:16 -0700
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Akinobu Mita <akinobu.mita@...il.com>, Christoph Lameter <cl@...ux.com>,
	David Rientjes <rientjes@...gle.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Mark Rutland <mark.rutland@....com>, Jiri Olsa <jolsa@...nel.org>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, bpf@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 3/4] mm, slab: add static key for should_failslab()

On Fri, May 31, 2024 at 11:33:34AM +0200, Vlastimil Babka wrote:
> Since commit 4f6923fbb352 ("mm: make should_failslab always available for
> fault injection") should_failslab() is unconditionally a noinline
> function. This adds visible overhead to the slab allocation hotpath,
> even if the function is empty. With CONFIG_FAILSLAB=y there's additional
> overhead when the functionality is not enabled by a boot parameter or
> debugfs.
> 
> The overhead can be eliminated with a static key around the callsite.
> Fault injection and error injection frameworks can now be told that the
> this function has a static key associated, and are able to enable and
> disable it accordingly.
> 
> Signed-off-by: Vlastimil Babka <vbabka@...e.cz>

Reviewed-by: Roman Gushchin <roman.gushchin@...ux.dev>