From: Peter Zijlstra <peterz@infradead•org>
To: Steven Rostedt <rostedt@goodmis•org>
Cc: Mike Rapoport <rppt@kernel•org>,
Andrew Morton <akpm@linux-foundation•org>,
Luis Chamberlain <mcgrof@kernel•org>,
Andreas Larsson <andreas@gaisler•com>,
Andy Lutomirski <luto@kernel•org>,
Ard Biesheuvel <ardb@kernel•org>, Arnd Bergmann <arnd@arndb•de>,
Borislav Petkov <bp@alien8•de>, Brian Cain <bcain@quicinc•com>,
Catalin Marinas <catalin.marinas@arm•com>,
Christoph Hellwig <hch@infradead•org>,
Christophe Leroy <christophe.leroy@csgroup•eu>,
Dave Hansen <dave.hansen@linux•intel.com>,
Dinh Nguyen <dinguyen@kernel•org>,
Geert Uytterhoeven <geert@linux-m68k•org>,
Guo Ren <guoren@kernel•org>, Helge Deller <deller@gmx•de>,
Huacai Chen <chenhuacai@kernel•org>,
Ingo Molnar <mingo@redhat•com>,
Johannes Berg <johannes@sipsolutions•net>,
John Paul Adrian Glaubitz <glaubitz@physik•fu-berlin.de>,
Kent Overstreet <kent.overstreet@linux•dev>,
"Liam R. Howlett" <Liam.Howlett@oracle•com>,
Mark Rutland <mark.rutland@arm•com>,
Masami Hiramatsu <mhiramat@kernel•org>,
Matt Turner <mattst88@gmail•com>,
Max Filippov <jcmvbkbc@gmail•com>,
Michael Ellerman <mpe@ellerman•id.au>,
Michal Simek <monstr@monstr•eu>, Oleg Nesterov <oleg@redhat•com>,
Palmer Dabbelt <palmer@dabbelt•com>,
Richard Weinberger <richard@nod•at>,
Russell King <linux@armlinux•org.uk>, Song Liu <song@kernel•org>,
Stafford Horne <shorne@gmail•com>,
Suren Baghdasaryan <surenb@google•com>,
Thomas Bogendoerfer <tsbogend@alpha•franken.de>,
Thomas Gleixner <tglx@linutronix•de>,
Uladzislau Rezki <urezki@gmail•com>,
Vineet Gupta <vgupta@kernel•org>, Will Deacon <will@kernel•org>,
bpf@vger•kernel.org, linux-alpha@vger•kernel.org,
linux-arch@vger•kernel.org, linux-arm-kernel@lists•infradead.org,
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sparclinux@vger•kernel.org, x86@kernel•org
Subject: Re: [PATCH v6 6/8] x86/module: prepare module loading for ROX allocations of text
Date: Thu, 17 Oct 2024 11:35:15 +0200 [thread overview]
Message-ID: <20241017093515.GU16066@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20241016170128.7afeb8b0@gandalf.local.home>
On Wed, Oct 16, 2024 at 05:01:28PM -0400, Steven Rostedt wrote:
> On Wed, 16 Oct 2024 15:24:22 +0300
> Mike Rapoport <rppt@kernel•org> wrote:
>
> > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> > index 8da0e66ca22d..b498897b213c 100644
> > --- a/arch/x86/kernel/ftrace.c
> > +++ b/arch/x86/kernel/ftrace.c
> > @@ -118,10 +118,13 @@ ftrace_modify_code_direct(unsigned long ip, const char *old_code,
> > return ret;
> >
> > /* replace the text with the new text */
> > - if (ftrace_poke_late)
> > + if (ftrace_poke_late) {
> > text_poke_queue((void *)ip, new_code, MCOUNT_INSN_SIZE, NULL);
> > - else
> > - text_poke_early((void *)ip, new_code, MCOUNT_INSN_SIZE);
> > + } else {
> > + mutex_lock(&text_mutex);
> > + text_poke((void *)ip, new_code, MCOUNT_INSN_SIZE);
> > + mutex_unlock(&text_mutex);
> > + }
> > return 0;
> > }
>
> So this slows down the boot by over 30ms. That may not sound like much, but
> we care very much about boot times. This code is serialized with boot and
> runs whenever ftrace is configured in the kernel. The way I measured this,
> was that I added:
>
> If this is only needed for module load, can we at least still use the
> text_poke_early() at boot up?
Right, so I don't understand why this is needed at all.
ftrace_module_init() runs before complete_formation() which normally
switches to ROX, as such ftrace should be able to continue to do direct
modifications here.
Which reminds me, at some point I did patches adding a
MODULE_STATE_UNFORMED callback in order for static_call / jump_label to
be able to avoid the expensive patching on module load as well (arguably
ftrace should be using that too, instead of a custom callback).
next prev parent reply other threads:[~2024-10-17 9:36 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-16 12:24 [PATCH v6 0/8] x86/module: use large ROX pages for text allocations Mike Rapoport
2024-10-16 12:24 ` [PATCH v6 1/8] mm: vmalloc: group declarations depending on CONFIG_MMU together Mike Rapoport
2024-10-16 14:41 ` Uladzislau Rezki
2024-10-19 22:17 ` Luis Chamberlain
2024-10-16 12:24 ` [PATCH v6 2/8] mm: vmalloc: don't account for number of nodes for HUGE_VMAP allocations Mike Rapoport
2024-10-16 17:21 ` Uladzislau Rezki
2024-10-19 22:19 ` Luis Chamberlain
2024-10-16 12:24 ` [PATCH v6 3/8] asm-generic: introduce text-patching.h Mike Rapoport
2024-10-19 22:21 ` Luis Chamberlain
2024-10-16 12:24 ` [PATCH v6 4/8] module: prepare to handle ROX allocations for text Mike Rapoport
2024-10-19 22:30 ` Luis Chamberlain
2024-10-16 12:24 ` [PATCH v6 5/8] arch: introduce set_direct_map_valid_noflush() Mike Rapoport
2024-10-19 22:32 ` Luis Chamberlain
2024-10-16 12:24 ` [PATCH v6 6/8] x86/module: prepare module loading for ROX allocations of text Mike Rapoport
2024-10-16 21:01 ` Steven Rostedt
2024-10-17 9:35 ` Peter Zijlstra [this message]
2024-10-17 11:25 ` Mike Rapoport
2024-10-17 15:35 ` Steven Rostedt
2024-10-17 14:17 ` Steven Rostedt
2024-10-19 12:07 ` Mike Rapoport
2024-10-21 22:15 ` Nathan Chancellor
2024-10-24 8:13 ` Mike Rapoport
2024-10-16 12:24 ` [PATCH v6 7/8] execmem: add support for cache of large ROX pages Mike Rapoport
2024-10-19 22:46 ` Luis Chamberlain
2024-10-16 12:24 ` [PATCH v6 8/8] x86/module: enable ROX caches for module text on 64 bit Mike Rapoport
2024-10-19 22:46 ` Luis Chamberlain
2024-10-19 22:51 ` [PATCH v6 0/8] x86/module: use large ROX pages for text allocations Luis Chamberlain
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