From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752486Ab1F3NMK (ORCPT ); Thu, 30 Jun 2011 09:12:10 -0400 Received: from na3sys009aog115.obsmtp.com ([74.125.149.238]:40944 "EHLO na3sys009aog115.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751382Ab1F3NMA convert rfc822-to-8bit (ORCPT ); Thu, 30 Jun 2011 09:12:00 -0400 MIME-Version: 1.0 In-Reply-To: References: <1309248717-14606-1-git-send-email-per.forlin@linaro.org> Date: Thu, 30 Jun 2011 18:41:57 +0530 Message-ID: Subject: Re: [PATCH v8 00/12] use nonblock mmc requests to minimize latency From: "S, Venkatraman" To: "Poddar, Sourav" Cc: Per Forlin , linaro-dev , Nicolas Pitre , linux-arm-kernel , linux-kernel , linux-mmc , Nickolay Nickolaev , Linus Walleij , Chris Ball Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 30, 2011 at 6:06 PM, Poddar, Sourav wrote: > On Tue, Jun 28, 2011 at 1:41 PM, Per Forlin wrote: >> How significant is the cache maintenance over head? >> It depends, the eMMC are much faster now >> compared to a few years ago and cache maintenance cost more due to >> multiple cache levels and speculative cache pre-fetch. In relation the >> cost for handling the caches have increased and is now a bottle neck >> dealing with fast eMMC together with DMA. >> >> The intention for introducing non-blocking mmc requests is to minimize the >> time between a mmc request ends and another mmc request starts. In the >> current implementation the MMC controller is idle when dma_map_sg and >> dma_unmap_sg is processing. Introducing non-blocking mmc request makes it >> possible to prepare the caches for next job in parallel to an active >> mmc request. >> >> This is done by making the issue_rw_rq() non-blocking. >> The increase in throughput is proportional to the time it takes to >> prepare (major part of preparations is dma_map_sg and dma_unmap_sg) >> a request and how fast the memory is. The faster the MMC/SD is >> the more significant the prepare request time becomes. Measurements on U5500 >> and Panda on eMMC and SD shows significant performance gain for large >> reads when running DMA mode. In the PIO case the performance is unchanged. >> >> There are two optional hooks pre_req() and post_req() that the host driver >> may implement in order to move work to before and after the actual mmc_request >> function is called. In the DMA case pre_req() may do dma_map_sg() and prepare >> the dma descriptor and post_req runs the dma_unmap_sg. >> >> Details on measurements from IOZone and mmc_test: >> https://wiki.linaro.org/WorkingGroups/Kernel/Specs/StoragePerfMMC-async-req >> >> Changes since v7: >>  * rebase on mmc-next, on top of Russell's updated error handling. >>  * Clarify description of mmc_start_req() >>  * Resolve compile without CONFIG_DMA_ENIGNE issue for mmci >>  * Add mmc test to measure how performance is affected by sg length >>  * Add missing wait_for_busy in mmc_test non-blocking test. This call got lost >>   in v4 of this patchset when refactoring mmc_start_req. >>  * Add sub-prefix (core block queue) to relevant patches. >> >> Per Forlin (12): >>  mmc: core: add non-blocking mmc request function >>  omap_hsmmc: add support for pre_req and post_req >>  mmci: implement pre_req() and post_req() >>  mmc: mmc_test: add debugfs file to list all tests >>  mmc: mmc_test: add test for non-blocking transfers >>  mmc: mmc_test: test to measure how sg_len affect performance >>  mmc: block: add member in mmc queue struct to hold request data >>  mmc: block: add a block request prepare function >>  mmc: block: move error code in issue_rw_rq to a separate function. >>  mmc: queue: add a second mmc queue request member >>  mmc: core: add random fault injection >>  mmc: block: add handling for two parallel block requests in >>    issue_rw_rq >> >>  drivers/mmc/card/block.c      |  505 ++++++++++++++++++++++++----------------- >>  drivers/mmc/card/mmc_test.c   |  491 ++++++++++++++++++++++++++++++++++++++-- >>  drivers/mmc/card/queue.c      |  184 ++++++++++------ >>  drivers/mmc/card/queue.h      |   33 ++- >>  drivers/mmc/core/core.c       |  167 +++++++++++++- >>  drivers/mmc/core/debugfs.c    |    5 + >>  drivers/mmc/host/mmci.c       |  147 +++++++++++- >>  drivers/mmc/host/mmci.h       |    8 + >>  drivers/mmc/host/omap_hsmmc.c |   87 +++++++- >>  include/linux/mmc/core.h      |    6 +- >>  include/linux/mmc/host.h      |   24 ++ >>  lib/Kconfig.debug             |   11 + >>  12 files changed, 1345 insertions(+), 323 deletions(-) > > > > Boot tested on Omap4430 Blaze board. > > Tested-by: Sourav Poddar > Reviewed for OMAP along with Sourav's tests.. Reviewed-by: Venkatraman S