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Date:      Thu, 4 Oct 2007 14:32:39 +0200 (CEST)
From:      Oliver Fromme <olli@lurza.secnetix.de>
To:        freebsd-stable@FreeBSD.ORG, matrix@itlegion.ru
Subject:   Re: Quation about HZ kernel option
Message-ID:  <200710041232.l94CWd6W056143@lurza.secnetix.de>
In-Reply-To: <02d401c805cb$abf59ec0$0c00a8c0@Artem>

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Artem Kuchin <> wrote:
 > What value of HZ option would you recommend 
 > for a hosting (web) server with a lot of processes
 > (about 900) and polling off (as decided from previous 
 > discussion polling is useless in
 > this situation).

In that case, I would recommend not to override the
default at all (which is 1000).

 > What parts of kernel does this option affect? What
 > depends on it? 

The value of HZ specifies the minimum timing quantum
of the kernel.  It affects the granularity of the
scheduler and all timing-related functions (nanosleep(2)
and others), and the accuracy of dummynet and polling.
I'm sure there are more things.

Basically, the kernel cannot handle time slices smaller
than 1/HZ seconds, for any purpose.

Best regards
   Oliver

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Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M.
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