2014-10-05 19:47 GMT+09:00 Chuck Ebbert <[email protected]>: > On Sun, 5 Oct 2014 15:02:56 +0900 > Akinobu Mita <[email protected]> wrote: > >> This makes CMA memory area size zero for x86 in default configuration >> (doesn't change on the other architectures). If default CMA size is >> zero, DMA_CMA is disabled. It can be enabled by passing cma= to the >> kernel. >> >> This makes less impact on x86. Because there is no mainline driver that >> requires it for x86, and Peter Hurley reported the performance >> regression, as this is trying to drive _all_ dma mapping allocations >> through a _very_ small window. >> >> Signed-off-by: Akinobu Mita <[email protected]> >> Reported-by: Peter Hurley <[email protected]> >> Cc: Peter Hurley <[email protected]> >> Cc: Chuck Ebbert <[email protected]> >> Cc: Marek Szyprowski <[email protected]> >> Cc: Konrad Rzeszutek Wilk <[email protected]> >> Cc: David Woodhouse <[email protected]> >> Cc: Don Dutile <[email protected]> >> Cc: Thomas Gleixner <[email protected]> >> Cc: Ingo Molnar <[email protected]> >> Cc: "H. Peter Anvin" <[email protected]> >> Cc: Andi Kleen <[email protected]> >> Cc: Yinghai Lu <[email protected]> >> Cc: [email protected] >> Cc: [email protected] >> --- >> drivers/base/Kconfig | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig >> index 4e7f0ff..92a5987e 100644 >> --- a/drivers/base/Kconfig >> +++ b/drivers/base/Kconfig >> @@ -240,6 +240,7 @@ comment "Default contiguous memory area size:" >> config CMA_SIZE_MBYTES >> int "Size in Mega Bytes" >> depends on !CMA_SIZE_SEL_PERCENTAGE >> + default 0 if X86 >> default 16 >> help >> Defines the size (in MiB) of the default memory area for Contiguous >> @@ -248,6 +249,7 @@ config CMA_SIZE_MBYTES >> config CMA_SIZE_PERCENTAGE >> int "Percentage of total memory" >> depends on !CMA_SIZE_SEL_MBYTES >> + default 0 if X86 >> default 10 >> help >> Defines the size of the default memory area for Contiguous Memory > > You probably need to add some documentation too. Jean Delvare proposed > the below, before your change. If the default is going to be zero on > x86, that information and some further help should be added to this.
OK, I'll add information in help text for CONFIG_CMA_SIZE_MBYTES and CONFIG_CMA_SIZE_PERCENTAGE. Jean's patch adds information in CONFIG_DMA_CMA, so this change doesn't conflict his patch. > ------------------------ > > From: Jean Delvare <[email protected]> > Subject: [PATCH] CMA: Document cma=0 > > It isn't obvious that CMA can be disabled on the kernel's command > line, so document it. > > Signed-off-by: Jean Delvare <[email protected]> > Cc: Joonsoo Kim <[email protected]> > Cc: Greg Kroah-Hartman <[email protected]> > --- > Documentation/kernel-parameters.txt | 3 ++- > drivers/base/Kconfig | 3 +++ > 2 files changed, 5 insertions(+), 1 deletion(-) > > --- linux-3.17-rc7.orig/Documentation/kernel-parameters.txt 2014-09-23 > 13:19:06.644838292 +0200 > +++ linux-3.17-rc7/Documentation/kernel-parameters.txt 2014-10-04 > 14:10:03.257579721 +0200 > @@ -656,7 +656,8 @@ bytes respectively. Such letter suffixes > Sets the size of kernel global memory area for > contiguous memory allocations and optionally the > placement constraint by the physical address range of > - memory allocations. For more information, see > + memory allocations. A value of 0 disables CMA > + altogether. For more information, see > include/linux/dma-contiguous.h > > cmo_free_hint= [PPC] Format: { yes | no } > --- linux-3.17-rc7.orig/drivers/base/Kconfig 2014-09-12 16:23:14.911353676 > +0200 > +++ linux-3.17-rc7/drivers/base/Kconfig 2014-10-04 13:41:37.672347240 +0200 > @@ -231,6 +231,9 @@ config DMA_CMA > to allocate big physically-contiguous blocks of memory for use with > hardware components that do not support I/O map nor scatter-gather. > > + You can disable CMA by specifying "cma=0" on the kernel's command > + line. > + > For more information see <include/linux/dma-contiguous.h>. > If unsure, say "n". > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
