Messages in this thread | | | Subject | Re: [PATCH] MIPS: Loongson: Make default kernel log buffer size as 128KB for Loongson3 | From | Tiezhu Yang <> | Date | Wed, 16 Oct 2019 10:23:10 +0800 |
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On 10/16/2019 02:53 AM, Paul Burton wrote: > Hi Tiezhu & Huacai, > > On Tue, Oct 15, 2019 at 12:00:25PM +0800, Tiezhu Yang wrote: >> On 10/15/2019 11:36 AM, Huacai Chen wrote: >>> On Tue, Oct 15, 2019 at 10:12 AM Tiezhu Yang <yangtiezhu@loongson.cn> wrote: >>>> When I update kernel with loongson3_defconfig based on the Loongson 3A3000 >>>> platform, then using dmesg command to show kernel ring buffer, the initial >>>> kernel messages have disappeared due to the log buffer is too small, it is >>>> better to change the default kernel log buffer size from 16KB to 128KB. >>>> >>>> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> >>>> --- >>>> arch/mips/configs/loongson3_defconfig | 2 +- >>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>> >>>> diff --git a/arch/mips/configs/loongson3_defconfig b/arch/mips/configs/loongson3_defconfig >>>> index 90ee008..3aa2201 100644 >>>> --- a/arch/mips/configs/loongson3_defconfig >>>> +++ b/arch/mips/configs/loongson3_defconfig >>>> @@ -12,7 +12,7 @@ CONFIG_TASKSTATS=y >>>> CONFIG_TASK_DELAY_ACCT=y >>>> CONFIG_TASK_XACCT=y >>>> CONFIG_TASK_IO_ACCOUNTING=y >>>> -CONFIG_LOG_BUF_SHIFT=14 >>>> +CONFIG_LOG_BUF_SHIFT=17 >>> Hi, Tiezhu, >>> >>> Why you choose 128KB but not 64KB or 256KB? I found 64KB is enough for >>> our cases. And if you really need more, I think 256KB could be better >>> because there are many platforms choose 256KB. >> Hi Huacai, >> >> Thanks for your reply and suggestion, I will send a v2 patch. > Thanks for the patches. > > I actually have a slight preference for 128KB if you've no specific > need, since 128KB is the default. Some quick grepping says that of 405 > defconfigs in tree (as of v5.4-rc3), we have: > > LOG_BUF_SHIFT Count > 12 1 > 13 3 > 14 235 > 15 18 > 16 39 > 17 90 > 18 13 > 19 2 > 20 4 > > ie. 16KiB is by far the most common, then second most common is the > default 128KiB. 256KiB is comparatively rare.
Hi Paul,
Thank you very much for your detailed explanation. I think 128KB is enough to save the boot messages because the dmesg output size is about 40KB after reboot in my system.
> > However, I don't think your v1 patch is quite right Tiezhu - since 17 is > the default it shouldn't be specified in the defconfig at all. Did you > manually make the change in the loongson3_defconfig file? If so please > take a look at the savedefconfig make target & try something like this: > > make ARCH=mips loongson3_defconfig > make ARCH=mips menuconfig > # Change LOG_BUF_SHIFT > make ARCH=mips savedefconfig > mv defconfig arch/mips/configs/loongson3_defconfig > git add -i arch/mips/configs/loongson3_defconfig > # Stage the relevant changes, drop the others > > You should end up with the CONFIG_LOG_BUF_SHIFT line just getting > deleted.
Yes, you are right, I will make a new patch followed with your steps and send a v3 patch: just delete the CONFIG_LOG_BUF_SHIFT line to use the default value 128KB and update the commit message.
> > If on the other hand you really do prefer 256KiB for these systems > please describe why in the commit message. It could be something as > simple as "we have lots of memory so using 256KiB isn't a big deal, and > gives us a better chance of preserving boot messages until they're > examined". But if your log is getting this big before you look at it (or > before something like systemd copies it into its journal), there's > probably something fishy going on.
Hi Huacai,
What do you think? If you have any more suggestion, please let me know.
Thanks,
Tiezhu Yang
> > Thanks, > Paul
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