Date: Sun, 18 Nov 2007 22:30:09 +0200 (EET) From: Charlie & <root@ranta.suonsivu.net> To: FreeBSD-gnats-submit@FreeBSD.org Subject: kern/118124: HZ value on slow computers Message-ID: <200711182030.lAIKU9fQ033870@ranta.suonsivu.net> Resent-Message-ID: <200711191350.lAJDo2Du050676@freefall.freebsd.org>
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>Number: 118124 >Category: kern >Synopsis: HZ value on slow computers >Confidential: no >Severity: serious >Priority: medium >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: change-request >Submitter-Id: current-users >Arrival-Date: Mon Nov 19 13:50:01 UTC 2007 >Closed-Date: >Last-Modified: >Originator: hsu@bbnetworks.net >Release: FreeBSD 6.2-STABLE i386 >Organization: bbnetworks.net >Environment: System: FreeBSD ranta.suonsivu.net 6.2-STABLE FreeBSD 6.2-STABLE #3: Sat Nov 17 15:33:51 EET 2007 root@ranta.suonsivu.net:/usr/obj/usr/src/sys/EBOX2300 i386 This is relevant to slow computers, such as anything based on SoC things, Sis550, Geode, very old computers. >Description: HZ was bumped to 1000 couple of years ago. This is fine for quick computers, but becomes a problem on old computers and various embedded devices. On Vortex86 cpu at 200MHz, and HZ set to 1000, with DUMMYNET and IPFW built into the kernel, cpu seems to spend around 12-14% of time in interrupt and overall performance is really low. >How-To-Repeat: Install FreeBSD on a slow computer. Try a 486, old pentiums, anything Sis550 or Geode based. Use a kernel with all firewall, dummynet and other heavy networking options on. >Fix: HZ should probably be dynamic, based on cpu, rather than a fixed value in kernel config. Workaround is setting HZ in loader.conf >Release-Note: >Audit-Trail: >Unformatted:
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