From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from uow.edu.au (wumpus.its.uow.edu.au [130.130.68.12]) by horus.its.uow.edu.au (8.9.3/8.9.3) with ESMTP id AAA08371 for ; Thu, 15 Mar 2001 00:24:17 +1100 (EST) Message-ID: <3AAF716E.1B776E31@uow.edu.au> Date: Thu, 15 Mar 2001 00:26:06 +1100 From: Andrew Morton MIME-Version: 1.0 Subject: it gets slower Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: "linux-mm@kvack.org" List-ID: After doing a huge amount of disk I/O the other day I noted that a subsequent full kernel build took *ages*. I haven't been able to reproduce the full extent of this, but.. Doing a build after boot takes 320 seconds. After copying two kernel trees and diffing them, an identical full build takes 336 seconds. Profiling each build says: Before: c01120b0 do_page_fault 1453 1.2440 c0271a00 __generic_copy_to_user 1741 29.0167 c0122c6c do_wp_page 1895 2.9609 c012da88 rmqueue 2245 3.7922 c0271a3c __generic_copy_from_user 3593 59.8833 c01260f0 file_read_actor 4490 41.5741 c0123388 do_anonymous_page 11121 89.6855 c01071c0 default_idle 21741 418.0962 00000000 total 71684 0.0469 After: c0271a00 __generic_copy_to_user 1696 28.2667 c0122c6c do_wp_page 1865 2.9141 c012da88 rmqueue 2226 3.7601 c0271a3c __generic_copy_from_user 3584 59.7333 c01260f0 file_read_actor 4529 41.9352 c0123388 do_anonymous_page 11324 91.3226 c01071c0 default_idle 34807 669.3654 00000000 total 90069 0.0590 This is a 1kHz profile, so we've spent an extra 13 seconds in default_idle. Doing I/O, presumably. 256 meg dual Celeron. Why? Also, we spent 12 seconds in do_anonymous_page and do_wp_page madly memsetting. Has anyone tried prezeroing some pages in default_idle(), so they're ready to go? Yes, I know it'll probably be cachely disadvantageous, but has anyone actually tried and measured it? -- 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.eu.org/Linux-MM/