From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [linux-lvm] LVM and *bad* performance (no striping) References: <200104111949.f3BJnFHt014761@webber.adilger.int> From: Terje Kvernes Date: 12 Apr 2001 00:00:05 +0200 In-Reply-To: Andreas Dilger's message of "Wed, 11 Apr 2001 13:49:14 -0600 (MDT)" Message-ID: MIME-Version: 1.0 Sender: linux-lvm-admin@sistina.com Errors-To: linux-lvm-admin@sistina.com Reply-To: linux-lvm@sistina.com List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-lvm@sistina.com Andreas Dilger writes: > Ok, the chain of events is as follows (hopefully correct): > > Non-LVM read LVM read > ------------ -------- > sys_read sys_read > block_read block_read > ll_rw_block ll_rw_block > submit_bh submit_bh > generic_make_request generic_make_request > lvm_make_request_fn > lvm_map > __make_request __make_request > > The rest should be the same because you have the same IDE driver > below. I'm going to stick my head in here and say thanks for that info. I really need to _read_ the code. *sigh* > Very strange. I just tested the same on my system, and LVM ends up > _faster_ than raw disk access in each of the 3 tests I did: okay, I only have the option of testing this on an old IDE drive, and the times where within 7% of eachother (LVM being the slower of the two on all runs). it's a bigger difference then I'd like to see, but it varies with runs, and the box is low on memory and being used at the same time. the only thing they're really saying is that LVM isn't a bottleneck. not that it'll help much in Urs' case though. :/ -- Terje