| Message ID | 20090402033227.GA11327@linux-sh.org (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
Paul Mundt wrote: > On Thu, Apr 02, 2009 at 12:25:19AM +0900, Shin-ichiro KAWASAKI wrote: >> Hi, Magnus! Thank you for your explanation. >> >> Magnus Damm wrote: >>> 2009/3/31 Shin-ichiro KAWASAKI <kawasaki@juno.dti.ne.jp>: >>>> I'd like to ask following questions to linux-sh experts, >>>> >>>> - Why such io-traps are used to access CF? >>>> - Will this io-traps are used for SH7785LCR's SD card access? >>>> >>>> I guess these io-traps can be the reason why gcc takes so much time on >>>> qemu-sh. >>> The r2d hardware implements 16-bit only CF interface while driver >>> software requires 8-bit access. To work around this issue io_trapped >>> is used to convert 8-bit accesses to 16-bit accesses. This is quite >>> slow. >>> >>> For more information, please see the comment in >>> arch/sh/boards/mach-r2d/setup.c >>> >>> To improve performance, consider adding a command line flag to the >>> kernel that disables io_trapped. This flag can then be set on the >>> kernel command line by the person running qemu. >>> >>> Hope this helps! >> It really helps! >> >> The attached patch is a rough implementation to add a command line >> flag 'avoid_trap', which Magnus suggested. It is just a reference, >> but it reduces the gcc compile time from 40 seconds to around 4 seconds. >> 10 times faster! >> >> Is it OK to add such qemu specific options to linux kernel mainline? >> > Sure, why not. Try this: It works fine, and gains same performance improvement as my dirty patch. Thank you Paul for your quick clean patch! Tested-by: Shin-ichiro KAWASAKI <kawasaki@juno.dti.ne.jp> > --- > > commit eeee7853c4ffaf5b9eb58f39708e3c78f66cee15 > Author: Paul Mundt <lethal@linux-sh.org> > Date: Thu Apr 2 12:31:16 2009 +0900 > > sh: Add a command line option for disabling I/O trapping. > > This adds a 'noiotrap' kernel command line option to permit disabling of > I/O trapping. This is mostly useful for running on emulators where the > physical device limitations are not an issue. > > Signed-off-by: Paul Mundt <lethal@linux-sh.org> > > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index 240257d..8b2067c 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -1544,6 +1544,8 @@ and is between 256 and 4096 characters. It is defined in the file > Valid arguments: on, off > Default: on > > + noiotrap [SH] Disables trapped I/O port accesses. > + > noirqdebug [X86-32] Disables the code which attempts to detect and > disable unhandled interrupt sources. > > diff --git a/arch/sh/kernel/io_trapped.c b/arch/sh/kernel/io_trapped.c > index 39cd7f3..c22853b 100644 > --- a/arch/sh/kernel/io_trapped.c > +++ b/arch/sh/kernel/io_trapped.c > @@ -14,6 +14,7 @@ > #include <linux/bitops.h> > #include <linux/vmalloc.h> > #include <linux/module.h> > +#include <linux/init.h> > #include <asm/system.h> > #include <asm/mmu_context.h> > #include <asm/uaccess.h> > @@ -32,6 +33,15 @@ EXPORT_SYMBOL_GPL(trapped_mem); > #endif > static DEFINE_SPINLOCK(trapped_lock); > > +static int trapped_io_disable __read_mostly; > + > +static int __init trapped_io_setup(char *__unused) > +{ > + trapped_io_disable = 1; > + return 1; > +} > +__setup("noiotrap", trapped_io_setup); > + > int register_trapped_io(struct trapped_io *tiop) > { > struct resource *res; > @@ -39,6 +49,9 @@ int register_trapped_io(struct trapped_io *tiop) > struct page *pages[TRAPPED_PAGES_MAX]; > int k, n; > > + if (unlikely(trapped_io_disable)) > + return 0; > + > /* structure must be page aligned */ > if ((unsigned long)tiop & (PAGE_SIZE - 1)) > goto bad; > -- > To unsubscribe from this list: send the line "unsubscribe linux-sh" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 240257d..8b2067c 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1544,6 +1544,8 @@ and is between 256 and 4096 characters. It is defined in the file Valid arguments: on, off Default: on + noiotrap [SH] Disables trapped I/O port accesses. + noirqdebug [X86-32] Disables the code which attempts to detect and disable unhandled interrupt sources. diff --git a/arch/sh/kernel/io_trapped.c b/arch/sh/kernel/io_trapped.c index 39cd7f3..c22853b 100644 --- a/arch/sh/kernel/io_trapped.c +++ b/arch/sh/kernel/io_trapped.c @@ -14,6 +14,7 @@ #include <linux/bitops.h> #include <linux/vmalloc.h> #include <linux/module.h> +#include <linux/init.h> #include <asm/system.h> #include <asm/mmu_context.h> #include <asm/uaccess.h> @@ -32,6 +33,15 @@ EXPORT_SYMBOL_GPL(trapped_mem); #endif static DEFINE_SPINLOCK(trapped_lock); +static int trapped_io_disable __read_mostly; + +static int __init trapped_io_setup(char *__unused) +{ + trapped_io_disable = 1; + return 1; +} +__setup("noiotrap", trapped_io_setup); + int register_trapped_io(struct trapped_io *tiop) { struct resource *res; @@ -39,6 +49,9 @@ int register_trapped_io(struct trapped_io *tiop) struct page *pages[TRAPPED_PAGES_MAX]; int k, n; + if (unlikely(trapped_io_disable)) + return 0; + /* structure must be page aligned */ if ((unsigned long)tiop & (PAGE_SIZE - 1)) goto bad;