From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx108.postini.com [74.125.245.108]) by kanga.kvack.org (Postfix) with SMTP id 87A586B009B for ; Mon, 29 Apr 2013 16:46:21 -0400 (EDT) Received: by mail-vc0-f178.google.com with SMTP id ha11so2176752vcb.23 for ; Mon, 29 Apr 2013 13:46:20 -0700 (PDT) Message-ID: <517EDC19.7020705@gmail.com> Date: Mon, 29 Apr 2013 16:46:17 -0400 From: KOSAKI Motohiro 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-2022-JP 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, kosaki.motohiro@gmail.com (4/22/13 11:23 AM), 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 > + may say n to override this. This should depend on CONFIG_EXPERT. Because this makes typically worse result on typical desktop machine. -- 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