Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753923Ab3DWB25 (ORCPT ); Mon, 22 Apr 2013 21:28:57 -0400 Received: from mail-pa0-f52.google.com ([209.85.220.52]:49773 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753507Ab3DWB24 (ORCPT ); Mon, 22 Apr 2013 21:28:56 -0400 From: vinayakm.list@gmail.com To: linux-mm@kvack.org Cc: akpm@linux-foundation.org, rientjes@google.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Vinayak Menon Subject: [PATCH v2] mm: add an option to disable bounce Date: Tue, 23 Apr 2013 06:58:26 +0530 Message-Id: <1366680506-2812-1-git-send-email-vinayakm.list@gmail.com> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1470 Lines: 44 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 | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/Kconfig b/mm/Kconfig index 3bea74f..e742d06 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -263,8 +263,14 @@ config ZONE_DMA_FLAG default "1" config BOUNCE - def_bool y + bool "Enable bounce buffers" + default 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 HIGHMEM is selected, but you + 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 -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/