From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: "Luck, Tony" <tony.luck@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Luming Yu <luming.yu@gmail.com>,
Christoph Hellwig <hch@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
"linux-ia64@vger.kernel.org" <linux-ia64@vger.kernel.org>,
"Yu, Fenghua" <fenghua.yu@intel.com>,
Felix Blyakher <felixb@sgi.com>,
"Li, Shaohua" <shaohua.li@intel.com>,
Bob Picco <bob.picco@hp.com>
Subject: RE: [RFC PATCH] Add TRACE_IRQFLAGS_SUPPORT, LOCKDEP_SUPPORT then enable ftrace for ia64
Date: Thu, 03 Sep 2009 10:46:30 +0200 [thread overview]
Message-ID: <1251967590.7447.0.camel@twins> (raw)
In-Reply-To: <57C9024A16AD2D4C97DC78E552063EA3E038DE7E@orsmsx505.amr.corp.intel.com>
On Wed, 2009-09-02 at 16:27 -0700, Luck, Tony wrote:
> >> diff -BruN linux-2.6.31-rc6/arch/ia64/include/asm/page.h
> >> linux-2.6.31-rc6-lockdep/arch/ia64/include/asm/page.h
> >> --- linux-2.6.31-rc6/arch/ia64/include/asm/page.h 2009-08-13
> >> 15:43:34.000000000 -0700
> >> +++ linux-2.6.31-rc6-lockdep/arch/ia64/include/asm/page.h 2009-08-23
> >> 18:59:00.000000000 -0700
> >> @@ -41,7 +41,7 @@
> >> #define PAGE_SIZE (__IA64_UL_CONST(1) << PAGE_SHIFT)
> >> #define PAGE_MASK (~(PAGE_SIZE - 1))
> >>
> >> -#define PERCPU_PAGE_SHIFT 16 /* log2() of max. size of per-CPU area */
> >> +#define PERCPU_PAGE_SHIFT 20 /*16 log2() of max. size of per-CPU area */
> >> #define PERCPU_PAGE_SIZE (__IA64_UL_CONST(1) << PERCPU_PAGE_SHIFT)
> >
> > Why was this seemingly unrelated change done in a lockdep patch?
>
> IIRC it is because the lockdep code needs a lot more percpu memory than the
> 64K that ia64 allocates.
>
> But I think that I'd prefer to only allocate the extra space when it
> is needed:
>
> #ifdef CONFIG_LOCKDEP
> #define PERCPU_PAGE_SHIFT 20 /* Need a Megabyte for lockdep */
> #else
> #define PERCPU_PAGE_SHIFT 16 /* 64K should be enough for normal use */
> #endif
Hmm, isn't all that percpu stuff in a special section, who's size you
can query at boot time and set-up accordingly?
next prev parent reply other threads:[~2009-09-03 8:46 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-28 3:18 [RFC PATCH] Add TRACE_IRQFLAGS_SUPPORT, LOCKDEP_SUPPORT then enable ftrace for ia64 Luming Yu
2009-08-28 6:22 ` Ingo Molnar
2009-09-02 23:27 ` Luck, Tony
2009-09-03 8:46 ` Peter Zijlstra [this message]
2009-09-03 16:02 ` Luck, Tony
2009-12-04 7:29 ` Luming Yu
2009-12-04 19:16 ` Luck, Tony
2009-12-05 3:19 ` Luming Yu
2009-12-07 5:56 ` Luming Yu
2009-12-07 21:35 ` Tony Luck
2009-12-08 12:25 ` Luming Yu
2009-12-09 6:45 ` Luming Yu
2009-12-09 8:52 ` Luming Yu
2009-12-09 18:11 ` Tony Luck
2009-12-09 18:22 ` Peter Zijlstra
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