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Received: by mailuser.nyi.internal (Postfix, from userid 501) id 45D57E00A8; Thu, 15 Oct 2020 23:38:21 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.3.0-489-gf39678d-fm-20201011.001-gf39678d0 Mime-Version: 1.0 Message-Id: In-Reply-To: References: <20201002063414.275161-1-andrew@aj.id.au> <20201002063414.275161-2-andrew@aj.id.au> Date: Fri, 16 Oct 2020 14:08:02 +1030 From: "Andrew Jeffery" To: "Joel Stanley" Subject: Re: [PATCH 1/3] ARM: dts: rainier: Add reserved memory for ramoops Content-Type: text/plain X-BeenThere: openbmc@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development list for OpenBMC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: OpenBMC Maillist Errors-To: openbmc-bounces+openbmc=archiver.kernel.org@lists.ozlabs.org Sender: "openbmc" On Tue, 6 Oct 2020, at 13:52, Joel Stanley wrote: > On Fri, 2 Oct 2020 at 06:35, Andrew Jeffery wrote: > > > > Reserve a 1MiB region of memory to record kmsg dumps and console state > > into 16kiB ring-buffer slots. The sizing allows for up to 32 dumps to be > > captured and read out. > > > > Signed-off-by: Andrew Jeffery > > --- > > arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts b/arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts > > index e6f422edf454..46a0e95049fd 100644 > > --- a/arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts > > +++ b/arch/arm/boot/dts/aspeed-bmc-ibm-rainier.dts > > @@ -47,6 +47,14 @@ reserved-memory { > > #size-cells = <1>; > > ranges; > > > > + ramoops@b7f00000 { > > + compatible = "ramoops"; > > + reg = <0xb7f00000 0x100000>; > > + record-size = <0x4000>; > > + console-size = <0x4000>; > > This is conserative. We've got plenty of space, how about we make it bigger? > > $ git grep console-size *.dts* | grep -Po "0x([0-9]+)" | xargs printf > "%x\n" | sort -n > 8000 > 8000 > 10000 > 10000 > 20000 > 20000 > 20000 > 20000 > 20000 > 60000 > 100000 > > The median is 128KB, which sounds reasonable. Well, maybe? Why should we basing it on what everyone else has done rather than what we need? We're compressing the data before it's written to the pstore ring. Uncompressed, 16k is in the order of 200 lines of text. With the default DEFLATE compression we can fit 3-4x more: root@rain15bmc:~# uptime 14:44:20 up 14:44, load average: 0.01, 0.01, 0.01 root@rain15bmc:~# dmesg | wc -l 640 root@rain15bmc:~# dmesg >/tmp/dmesg root@rain15bmc:~# stat -c "%s" /tmp/dmesg 44032 root@rain15bmc:~# gzip /tmp/dmesg root@rain15bmc:~# stat -c "%s" /tmp/dmesg.gz 11059 I think 16k is more than enough for now? > > $ git grep record-size *.dts* | grep -Po "0x([0-9]+)" | xargs printf "%x\n" > 20000 > 400 > 400 > 20000 > 20000 > 20000 > 10000 > 10000 > 10000 > 10000 > 20000 > > 64KB is the median record size. > > > + pmsg-size = <0x4000>; > > Do we want to add ftrace too? I figured getting an oops/panic stack dump might be enough for the moment. > > Should we also add max-reason = KMSG_DUMP_EMERG? > > Logging reboots and shutdowns is informative (you know if a reboot was > intentional or due to a crash that wasn't recorded) and allows for > testing. Yeah, that's a good idea. Thanks. Andrew