Date: Wed, 23 Nov 2022 01:16:55 +0900 From: Tomoaki AOKI <junchoon@dec.sakura.ne.jp> To: Dan Mack <mack@macktronics.com> Cc: Alexander Kabaev <kabaev@gmail.com>, freebsd-current@freebsd.org Subject: Re: dmesg content lifetime Message-ID: <20221123011655.c6a00ee21636e45e8b4f3a69@dec.sakura.ne.jp> In-Reply-To: <c4272589-572a-26a1-7e1e-6ffbe66fc615@macktronics.com> References: <9d519f-ce87-72d-dc6-789817468974@macktronics.com> <20221122104445.4ed88f6f@kan> <c4272589-572a-26a1-7e1e-6ffbe66fc615@macktronics.com>
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On Tue, 22 Nov 2022 09:47:10 -0600 (CST) Dan Mack <mack@macktronics.com> wrote: > On Tue, 22 Nov 2022, Alexander Kabaev wrote: > > > On Tue, 22 Nov 2022 09:12:28 -0600 (CST) > > Dan Mack <mack@macktronics.com> wrote: > > > >> It seems like dmesg content ages out over time. Is there a way to > >> leave the contents based on a fixed memory size instead? > >> > >> Dan > >> > > I think this is how it works: the kernel message bugger is of fixed > > size and kernel and syslog sequences (dmesg -a) share it. The other > > syslog users eventually puts enough content in there to displace all of > > kernel messages. If the kernel stays quiet, 'dmesg' then returns > > nothing, as by default it filters syslog entries that do not KERN > > facility out, see sbin/dmesg/dmesg.c. > > > > -- > > Alexander Kabaev > > > > Thank you Alexander, I did not know this. I'll USL (use-the-source-luke) > :-) > > Dan Increase kern.msgbufsize tunable on /boot/loader.conf if you want dmesg to live longer. For example, recommended value by iwlwifi team is 1146880. Much larger than default. Note that this is actually a tunable and can be set only on boot time. -- Tomoaki AOKI <junchoon@dec.sakura.ne.jp>
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