From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from www84.your-server.de ([213.133.104.84]) by bombadil.infradead.org with esmtps (Exim 4.69 #1 (Red Hat Linux)) id 1O4I09-0000iB-7S for linux-mtd@lists.infradead.org; Tue, 20 Apr 2010 18:16:49 +0000 Subject: Re: [PATCH] Fix a huge latency problem in the MTD CFI and LPDDR flash drivers. From: Stefani Seibold To: linux-mtd@lists.infradead.org In-Reply-To: <1271623604.7050.0.camel@wall-e.seibold.net> References: <1271623604.7050.0.camel@wall-e.seibold.net> Content-Type: text/plain; charset="ISO-8859-15" Date: Tue, 20 Apr 2010 20:16:31 +0200 Message-ID: <1271787391.16051.4.camel@wall-e.seibold.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Cc: akpm@linux-foundation.org, David Woodhouse , linux-kernel@vger.kernel.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Is the MTD mailing list routed to /dev/null? It is very sad that nobody gives my a reply. I ask for a merge for the patch, and if there any reason why not, it would be great to know. Otherwise i can't fix it. So again, please merge the path for the huge latency problem. Am Sonntag, den 18.04.2010, 22:46 +0200 schrieb Stefani Seibold: > From: Stefani Seibold > > The use of a memcpy() during a spinlock operation will cause very long > thread context switch delays if the flash chip bandwidth is low and the > data to be copied large, because a spinlock will disable preemption. > > For example: A flash with 6,5 MB/s bandwidth will cause under ubifs, > which request sometimes 128 KB (the flash erase size), a preemption delay of > 20 milliseconds. High priority threads will not be served during this > time, regardless whether this threads access the flash or not. This behavior > breaks real time. > > The patch changes all the use of spin_lock operations for xxxx->mutex > into mutex operations, which is exact what the name says and means. > > I have checked the code of the drivers and there is no use of atomic > pathes like interrupt or timers. The mtdoops facility will also not be used > by this drivers. So it is dave to replace the spin_lock against mutex. > > There is no performance regression since the mutex is normally not > acquired. > > Changelog: > 06.03.2010 First release > 26.03.2010 Fix mutex[1] issue and tested it for compile failure > > Signed-off-by: Stefani Seibold > --- > drivers/mtd/chips/cfi_cmdset_0001.c | 131 +++++++++++++++++----------------- > drivers/mtd/chips/cfi_cmdset_0002.c | 122 ++++++++++++++++---------------- > drivers/mtd/chips/cfi_cmdset_0020.c | 136 +++++++++++++++++----------------- > drivers/mtd/chips/fwh_lock.h | 6 +- > drivers/mtd/chips/gen_probe.c | 3 +- > drivers/mtd/lpddr/lpddr_cmds.c | 79 ++++++++++---------- > include/linux/mtd/flashchip.h | 4 +- > 7 files changed, 239 insertions(+), 242 deletions(-)