option HZ=?
Greetings, I want to know what is the bad effect of increasing HZ too much? And when is too much? What problems can I expect when HZ2000? Can I change this value without pre-compiling the kernel? Because all docs I found for HZ is in src/sys/conf/NOTES and it doesn't say much. How can I know if my kernel misses ticks? -- Best Wishes, Stefan Lambrev ICQ# 24134177 ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
RE: option HZ=?
I want to know what is the bad effect of increasing HZ too much? And when is too much? What problems can I expect when HZ2000? Can I change this value without pre-compiling the kernel? You can set kern.hz in /boot/loader.conf Robin P. Blanchard Systems Administrator Information Technology Outreach Services Carl Vinson Institute of Government The University of Georgia fon 706.542.6295 // fax 706.542.6535 ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: option HZ=?
On Wed, Jan 30, 2008 at 02:55:30PM +0200, Stefan Lambrev wrote: Greetings, I want to know what is the bad effect of increasing HZ too much? And when is too much? What problems can I expect when HZ2000? Can I change this value without pre-compiling the kernel? You can change HZ by adding a line to /boot/loader.conf like this: kern.hz=100 (it works on RELENG_6 and RELENG_7 and I'm using this conservative setting on all my boxes, since I don't need faster context switching) If you set HZ too high, the kernel will spend too much overhead on unnecessary context switching, and it may even reach a point (with very high values of HZ) where interrupt service routines get interrupted way too often by clock ticks; i.e. interrupts would eventually come in faster than the kernel can service them. Because all docs I found for HZ is in src/sys/conf/NOTES and it doesn't say much. -cpghost. -- Cordula's Web. http://www.cordula.ws/ ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: option HZ=?
cpghost wrote: On Wed, Jan 30, 2008 at 02:55:30PM +0200, Stefan Lambrev wrote: Greetings, I want to know what is the bad effect of increasing HZ too much? And when is too much? What problems can I expect when HZ2000? Can I change this value without pre-compiling the kernel? You can change HZ by adding a line to /boot/loader.conf like this: kern.hz=100 (it works on RELENG_6 and RELENG_7 and I'm using this conservative setting on all my boxes, since I don't need faster context switching) If you set HZ too high, the kernel will spend too much overhead on unnecessary context switching, and it may even reach a point (with very high values of HZ) where interrupt service routines get interrupted way too often by clock ticks; i.e. interrupts would eventually come in faster than the kernel can service them. Isn't there also something bad about TCP timestamp overflow? ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: option HZ=?
cpghost wrote: On Wed, Jan 30, 2008 at 02:55:30PM +0200, Stefan Lambrev wrote: Greetings, I want to know what is the bad effect of increasing HZ too much? And when is too much? What problems can I expect when HZ2000? Can I change this value without pre-compiling the kernel? You can change HZ by adding a line to /boot/loader.conf like this: kern.hz=100 Is there a way to see which value is in effect? # sysctl kern.hz sysctl: unknown oid 'kern.hz' ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: option HZ=?
Greetings, Dominic Fandrey wrote: cpghost wrote: On Wed, Jan 30, 2008 at 02:55:30PM +0200, Stefan Lambrev wrote: Greetings, I want to know what is the bad effect of increasing HZ too much? And when is too much? What problems can I expect when HZ2000? Can I change this value without pre-compiling the kernel? You can change HZ by adding a line to /boot/loader.conf like this: kern.hz=100 Is there a way to see which value is in effect? # sysctl kern.hz sysctl: unknown oid 'kern.hz' sysctl kern.clockrate will report this, and few other things. -- Best Wishes, Stefan Lambrev ICQ# 24134177 ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
