From mboxrd@z Thu Jan 1 00:00:00 1970 From: vinayakm.list@gmail.com (vinayak) Date: Mon, 22 Apr 2013 23:48:51 +0530 Subject: [PATCH] mm: add an option to disable bounce In-Reply-To: <20130422174712.GS14496@n2100.arm.linux.org.uk> References: <1366644180-6140-1-git-send-email-vinayakm.list@gmail.com> <20130422174712.GS14496@n2100.arm.linux.org.uk> Message-ID: <51757F0B.1090104@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Monday 22 April 2013 11:17 PM, Russell King - ARM Linux wrote: > On Mon, Apr 22, 2013 at 08:53:00PM +0530, vinayakm.list at gmail.com wrote: >> From: Vinayak Menon >> >> There are times when HIGHMEM is enabled, but >> we don't prefer CONFIG_BOUNCE to be enabled. >> CONFIG_BOUNCE can reduce the block device >> throughput, and this is not ideal for machines >> where we don't gain much by enabling it. So >> provide an option to deselect CONFIG_BOUNCE. The >> observation was made while measuring eMMC throughput >> using iozone on an ARM device with 1GB RAM. >> >> Signed-off-by: Vinayak Menon >> --- >> mm/Kconfig | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/mm/Kconfig b/mm/Kconfig >> index 3bea74f..29f9736 100644 >> --- a/mm/Kconfig >> +++ b/mm/Kconfig >> @@ -263,8 +263,14 @@ config ZONE_DMA_FLAG >> default "1" >> >> config BOUNCE >> + bool "Enable bounce buffers" >> def_bool y >> depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) > > I don't think this is correct. You shouldn't use "bool" with "def_bool". > Sure, add the "bool", but also change "def_bool" to "default". Yes. I will change it to "default" and this looks to be correct even from the definition in kconfig-language.txt. But I see other instances in mm/Kconfig, where bool and def_bool are used together. When I had tested this patch with def_bool, it worked as expected.