From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.nokia.com ([192.100.105.134] helo=mgw-mx09.nokia.com) by bombadil.infradead.org with esmtps (Exim 4.69 #1 (Red Hat Linux)) id 1LRnAB-0006lT-2E for linux-mtd@lists.infradead.org; Tue, 27 Jan 2009 12:35:33 +0000 Subject: Re: UBIFS performance with no_chk_data_crc option From: Artem Bityutskiy To: Reuben Dowle In-Reply-To: <70F6AAAFDC054F41B9994A9BCD3DF64E08308B18@exch01-aklnz.MARINE.NET.INT> References: <70F6AAAFDC054F41B9994A9BCD3DF64E08308B18@exch01-aklnz.MARINE.NET.INT> Content-Type: text/plain; charset="UTF-8" Date: Tue, 27 Jan 2009 14:35:12 +0200 Message-Id: <1233059712.7085.7.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: linux-mtd@lists.infradead.org Reply-To: dedekind@infradead.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2009-01-27 at 13:09 +1300, Reuben Dowle wrote: > It seems to me that enabling the no_chk_data_crc option actually causes > SLOWER read performance. I get these results: Reuben, thanks for noticing this. We've fixed the issue. You may find the fix in the linux-next branch of the ubifs-2.6.git tree: commit 6f7ab6d458bbfc2f55d295fa3e6b9e69cdb1d517 Author: Artem Bityutskiy Date: Tue Jan 27 16:12:31 2009 +0200 UBIFS: fix no_chk_data_crc When data CRC checking is disabled, UBIFS returns incorrect return code from the 'try_read_node()' function (0 instead of 1, which means CRC error), which make the caller re-read the data node again, but using a different code patch, so the second read is fine. Thus, we read the same node twice. And the result of this is that UBIFS is slower with no_chk_data_crc option than it is with chk_data_crc option. This patches fixes the problem. Reported-by: Reuben Dowle Signed-off-by: Artem Bityutskiy This patch has also been pushed to all UBIFS back-port git trees. -- Best regards, Artem Bityutskiy (Битюцкий Артём)