From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx142.postini.com [74.125.245.142]) by kanga.kvack.org (Postfix) with SMTP id DDF7D6B0002 for ; Mon, 22 Apr 2013 12:58:36 -0400 (EDT) Message-ID: <51756C24.8060505@infradead.org> Date: Mon, 22 Apr 2013 09:58:12 -0700 From: Randy Dunlap MIME-Version: 1.0 Subject: Re: [PATCH] mm: add an option to disable bounce References: <1366644180-6140-1-git-send-email-vinayakm.list@gmail.com> In-Reply-To: <1366644180-6140-1-git-send-email-vinayakm.list@gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: vinayakm.list@gmail.com Cc: linux-mm@kvack.org, akpm@linux-foundation.org, rientjes@google.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org On 04/22/13 08:23, vinayakm.list@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) > + help > + Enable bounce buffers for devices that cannot access > + the full range of memory available to the CPU. Enabled > + by default when ZONE_DMA or HIGMEM is selected, but you HIGHMEM > + may say n to override this. > > # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often > # have more than 4GB of memory, but we don't currently use the IOTLB to present > -- ~Randy -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org