From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Performance of Readv and the Cost of Revesemaps Under Heavy DB Workloads Message-ID: From: "Peter Wong" Date: Mon, 9 Sep 2002 15:07:08 -0500 MIME-Version: 1.0 Content-type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: linux-mm@kvack.org Cc: riel@nl.linux.org, akpm@zip.com.au, mjbligh@us.ibm.com, wli@holomorphy.com, dmccr@us.ibm.comgh@us.ibm.com, Bill Hartner , Troy C Wilson List-ID: All, I have measured a decision support workload using 2.4.17-based kernel, 2.5.31-based kernel, and 2.5.32-based kernel, all of which use the readv patch made available by Janet Morgan. Janet's patch is also included in Andrew Morton's mm patch, which can be found at http://www.zip.com.au/~akpm/linux/patches/2.5/2.5.32/2.5.32-mm2/. I got the following results. --------------------------------------------------------------- Database Size: 100 GB 2417RV: 2.4.17 (kernel.org) + lse04-rc1.diffs - bounce patch by Jens Axboe - io_reqeust_lock patch by Jonathan Lahr - rawvary patch by Badari Pulavarty - readv patches by Janet Morgan + TASK_UNMAPPED_BASE = 0x10000000 + PAGE_OFFSET = 0xD0000000 2531RV: 2.5.31 (kernel.org) + readv patch from Janet Morgan + TASK_UNMAPPED_BASE = 0x10000000 + PAGE_OFFSET = 0xC0000000 2532RV: 2.5.32 (kernel.org) + mm-2 patch from Andrew Morton which includes Janet's readv patch + TASK_UNMAPPED_BASE = 0x10000000 + PAGE_OFFSET = 0xC0000000 Based upon the throughput rate, 2531RV is 99.8% of 2417RV; 2532RV is 100% of 2417RV. There are 110 prefetchers for the runs, and ~2 GB of shared memory space used by the database, i.e., ~500,000 pages. With Andrew's mm patch, the maximum number of reversemaps reaches 43.7 millions. That is, each page is used by ~87 processes. With 8 bytes per reversemap, it costs ~350MB of the kernel memory, which is quite significant. Note that the database system used forks processes and does not use pthreads. Regards, Peter Peter Wai Yee Wong IBM Linux Technology Center, Performance Analysis email: wpeter@us.ibm.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/