linux-kernel - Re: [PATCH] mm/migrate: Mark unmap_and_move() "noinline" to avoid ICE in gcc 4.7.3

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Message-Id: <20150401124007.20c440cc43a482f698f461b8@linux-foundation.org>
Date:	Wed, 1 Apr 2015 12:40:07 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Kevin Hilman <khilman@...nel.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Simon Horman <horms@...ge.net.au>,
	Tyler Baker <tyler.baker@...aro.org>,
	Nishanth Menon <nm@...com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-sh@...r.kernel.org" <linux-sh@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Magnus Damm <magnus.damm@...il.com>,
	"grygorii.strashko@...aro.org" <grygorii.strashko@...aro.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] mm/migrate: Mark unmap_and_move() "noinline" to avoid
 ICE in gcc 4.7.3

On Wed, 01 Apr 2015 10:47:49 +0100 Marc Zyngier <marc.zyngier@....com> wrote:

> > -static int unmap_and_move(new_page_t get_new_page, free_page_t put_new_page,
> > -			unsigned long private, struct page *page, int force,
> > -			enum migrate_mode mode)
> > +static noinline int unmap_and_move(new_page_t get_new_page,
> > +				   free_page_t put_new_page,
> > +				   unsigned long private, struct page *page,
> > +				   int force, enum migrate_mode mode)
> >  {
> >  	int rc = 0;
> >  	int *result = NULL;
> > 
> 
> Ouch. That's really ugly. And on 32bit ARM, we end-up spilling half of
> the parameters on the stack, which is not going to help performance
> either (not that this would be useful on 32bit ARM anyway...).
> 
> Any chance you could make this dependent on some compiler detection
> mechanism?

With my arm compiler (gcc-4.4.4) the patch makes no difference -
unmap_and_move() isn't being inlined anyway.

How does this look?

Kevin, could you please retest?  I might have fat-fingered something...

--- a/mm/migrate.c~mm-migrate-mark-unmap_and_move-noinline-to-avoid-ice-in-gcc-473-fix
+++ a/mm/migrate.c
@@ -901,10 +901,20 @@ out:
 }
 
 /*
+ * gcc-4.7.3 on arm gets an ICE when inlining unmap_and_move().  Work around
+ * it.
+ */
+#if GCC_VERSION == 40703 && defined(CONFIG_ARM)
+#define ICE_noinline noinline
+#else
+#define ICE_noinline
+#endif
+
+/*
  * Obtain the lock on page, remove all ptes and migrate the page
  * to the newly allocated page in newpage.
  */
-static noinline int unmap_and_move(new_page_t get_new_page,
+static ICE_noinline int unmap_and_move(new_page_t get_new_page,
 				   free_page_t put_new_page,
 				   unsigned long private, struct page *page,
 				   int force, enum migrate_mode mode)
_

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