Date: Wed, 7 Apr 2021 16:08:36 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: current@freebsd.org Subject: Re: console getty uses 1.5% of CPU Message-ID: <20210407130836.GA80160@zxy.spb.ru> In-Reply-To: <69119.1617772960@critter.freebsd.dk> References: <69119.1617772960@critter.freebsd.dk>
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On Wed, Apr 07, 2021 at 05:22:40AM +0000, Poul-Henning Kamp wrote: > I have two 12.2-R systems where the serial console is attached to a terminal server. > > When there are no TCP connections to the terminal server, getty soaks up 1.5% of the > CPU in the kernel (sleeping in "ttyin"), ktrace shows no system calls. > > When a TCP connection is made to the terminal server, which raises the modem-handshake > on the DE-9 connector, the CPU usage stops. > > Anybody else seeing something like this ? Problem of comparing low number? Top's "getty 1.5% of the CPU" is not "getty eat 1.5% of the ALL CPU power", this is "getty 1.5% of off all other curerent eats of CPU power". T.e. if all system eat 985 ticks of CPU each second and getty eat 15 ticks of CPU each second -- top show 1.5% for getty. Load is raised to 99_985 ticks for system, getty eat 15 ticks -- top show 0% ( 15/(99985+15) = .015% ).
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