[LEDE-DEV] [OpenWrt-Devel] latency on PPPoA ADSL Annex A on using Lantiq

Daniel Niasoff daniel at redactus.co.uk
Thu Aug 18 04:26:28 PDT 2016 

Hi John

Tried it but it hadn't helped.

Just to confirm I followed the right steps. Did a make clean and then edited this file /home/build/openwrt/build_dir/toolchain-mips_34kc+dsp_gcc-5.3.0_musl-1.1.14/linux-4.4.7/net/atm/common.c

Then did a make

Thanks

Daniel
-----Original Message-----
From: John Crispin [mailto:john at phrozen.org] 
Sent: 18 August 2016 07:00
To: Daniel Niasoff <daniel at redactus.co.uk>; Mathias Kresin <dev at kresin.me>
Subject: Re: [OpenWrt-Devel] latency on PPPoA ADSL Annex A on using Lantiq

not much ahs changed in the kernel atm subsystem between 3.18 and 4.1

long shot, try to revert this patch

commit 7424ce65065852bdf7a040bf2490da4a8fc4b464
Author: Al Viro <viro at zeniv.linux.org.uk>
Date:   Thu Nov 20 07:01:29 2014 -0500

[atm] switch vcc_sendmsg() to copy_from_iter()

    ... and make it handle multi-segment iovecs - deals with that
    "fix this later" issue for free.  A bit of shame, really - it
    had been there since 2.3.15pre3 when the whole thing went into the
    tree, practically a historical artefact by now...

    Signed-off-by: Al Viro <viro at zeniv.linux.org.uk>

i'll compare owrt 3.18/4. patches next

	John





On 18/08/2016 07:33, John Crispin wrote:
> i would guess a regression inside the atm subsystem of he kernel or 
> some other part of the network stack. assuming that this issue is only 
> observed inside the atm part, i'll start looking there.
> 
> 	John
> 
> On 18/08/2016 06:22, Daniel Niasoff wrote:
>> Hi Mathias,
>>
>>
>> Looks like it's this commit that introduced the issue
>>
>>
>> https://git.openwrt.org/openwrt.git?p=openwrt.git;a=commitdiff;h=f9eb
>> 558f08c577d216d39c25d0572facc18a3ac1
>>
>>
>> -KERNEL_PATCHVER:=3.18
>> +KERNEL_PATCHVER:=4.1
>>
>> must be something in version 4.1 kernel. I guess it doesn't help very  much.
>>
>>
>> I tried to downgrade the latest commit back to a version 3.18 kernel 
>> by reversing the above change but wasn't able to compile. I had this 
>> error
>>
>>
>> make -f ./scripts/Makefile.build
>> obj=/home/build/openwrt/build_dir/target-mips_34kc+dsp_musl-1.1.14/linux-lantiq_xrx200/ltq-atm-vr9
>>   mips-openwrt-linux-musl-gcc
>> -Wp,-MD,/home/build/openwrt/build_dir/target-mips_34kc+dsp_musl-1.1.1
>> 4/linux-lantiq_xrx200/ltq-atm-vr9/.ltq_atm.o.d
>>  -nostdinc -isystem
>> /home/build/openwrt/staging_dir/toolchain-mips_34kc+dsp_gcc-5.3.0_mus
>> l-1.1.14/lib/gcc/mips-openwrt-linux-musl/5.3.0/include
>> -I./arch/mips/include -Iarch/mips/include/generated  -Iinclude 
>> -I./arch/mips/include/uapi -Iarch/mips/include/generated/uapi
>> -I./include/uapi -Iinclude/generated/uapi -include 
>> ./include/linux/kconfig.h -D__KERNEL__
>> -DVMLINUX_LOAD_ADDRESS=0xffffffff88002000 -DDATAOFFSET=0 -Wall 
>> -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing 
>> -fno-common -Werror-implicit-function-declaration 
>> -Wno-format-security -std=gnu89 -mno-check-zero-division -mabi=32 -G 
>> 0 -mno-abicalls -fno-pic -pipe -mno-branch-likely -msoft-float 
>> -DGAS_HAS_SET_HARDFLOAT -Wa,-msoft-float -ffreestanding -march=r4600 
>> -Wa,--trap
>> -I./arch/mips/include/asm/mach-ip22
>> -I./arch/mips/include/asm/mach-generic 
>> -fno-delete-null-pointer-checks
>> -O2 -fno-reorder-blocks -fno-tree-ch -fno-caller-saves
>> --param=allow-store-data-races=0 -Wframe-larger-than=1024 
>> -fstack-protector -Wno-unused-but-set-variable -fomit-frame-pointer 
>> -fno-var-tracking-assignments -g -femit-struct-debug-baseonly 
>> -fno-var-tracking -Wdeclaration-after-statement -Wno-pointer-sign 
>> -fno-strict-overflow -fconserve-stack -Werror=implicit-int 
>> -Werror=strict-prototypes -Werror=date-time -DCC_HAVE_ASM_GOTO  
>> -DMODULE -mno-long-calls -DCONFIG_VR9 -D"KBUILD_STR(s)=#s"
>> -D"KBUILD_BASENAME=KBUILD_STR(ltq_atm)"
>>  -D"KBUILD_MODNAME=KBUILD_STR(ltq_atm_vr9)" -c -o 
>> /home/build/openwrt/build_dir/target-mips_34kc+dsp_musl-1.1.14/linux-
>> lantiq_xrx200/ltq-atm-vr9/ltq_atm.o
>> /home/build/openwrt/build_dir/target-mips_34kc+dsp_musl-1.1.14/linux-
>> lantiq_xrx200/ltq-atm-vr9/ltq_atm.c
>> /home/build/openwrt/build_dir/target-mips_34kc+dsp_musl-1.1.14/linux-lantiq_xrx200/ltq-atm-vr9/ltq_atm.c:46:24:
>> fatal error: lantiq_soc.h: No such file or directory compilation 
>> terminated.
>> make[5]: ***
>> [/home/build/openwrt/build_dir/target-mips_34kc+dsp_musl-1.1.14/linux
>> -lantiq_xrx200/ltq-atm-vr9/ltq_atm.o]
>> Error 1
>> make[4]: ***
>> [_module_/home/build/openwrt/build_dir/target-mips_34kc+dsp_musl-1.1.
>> 14/linux-lantiq_xrx200/ltq-atm-vr9]
>> Error 2
>> make[4]: Leaving directory
>> `/home/build/openwrt/build_dir/target-mips_34kc+dsp_musl-1.1.14/linux-lantiq_xrx200/linux-3.18.29'
>> make[3]: ***
>> [/home/build/openwrt/build_dir/target-mips_34kc+dsp_musl-1.1.14/linux
>> -lantiq_xrx200/ltq-atm-vr9/.built]
>> Error 2
>> make[3]: Leaving directory
>> `/home/build/openwrt/package/kernel/lantiq/ltq-atm'
>> make[2]: *** [package/kernel/lantiq/ltq-atm/compile] Error 2
>> make[2]: Leaving directory `/home/build/openwrt'
>> make[1]: ***
>> [/home/build/openwrt/staging_dir/target-mips_34kc+dsp_musl-1.1.14/sta
>> mp/.package_compile]
>> Error 2
>> make[1]: Leaving directory `/home/build/openwrt'
>>
>> Thanks
>>
>> Daniel
>>
>>
>>
>>
>>
>>
>>
>> ---------------------------------------------------------------------
>> ---
>> *From:* Mathias Kresin <dev at kresin.me>
>> *Sent:* 10 August 2016 22:39
>> *To:* Daniel Niasoff
>> *Cc:* openwrt-devel at lists.openwrt.org; lede-dev at lists.infradead.org;
>> (leon at darkk.net.ru)
>> *Subject:* Re: [OpenWrt-Devel] latency on PPPoA ADSL Annex A on using 
>> Lantiq
>>  
>> Am 10.08.2016 um 22:41 schrieb Daniel Niasoff:
>>> Hi Mathias,
>>>
>>>  ADSL works fine on chaos calmer and I cannot reproduce the issue, so it looks like it's a recently introduced issue.
>>>
>>> Thanks for the idea, it should make it easier to pinpoint
>>>
>>> Any idea's where the issue might be?
>>
>> Nope, no idea yet. Might be a kernel update or something completely 
>> unexpected. Without knowing the commit that introduced the regression 
>> it's more or less crystal ball reading.
>>
>> Using 'git bisect' it should be easy to identify the faulty commit. 
>> It has to be somewhere between the last commit before chaos calmer 
>> was branched (git hash 6c9b1a278e484a9c7c5ff36f91da90f725776d00) and HEAD.
>>
>> git bisect tells me that you have to build and test circa 12 images 
>> to find the faulty commit:
>>
>> git clone "https://github.com/openwrt/openwrt.git"
>> <https://github.com/openwrt/openwrt.git>
>> 	
>> openwrt/openwrt <https://github.com/openwrt/openwrt.git>
>> github.com
>> openwrt - Linux distribution for embedded devices
>>
>>
>>
>> git checkout master
>> git bisect start HEAD 6c9b1a278e484a9c7c5ff36f91da90f725776d00
>> Bisecting: 1688 revisions left to test after this (roughly 11 steps)
>>
>> It might be a good idea to verify that
>> 6c9b1a278e484a9c7c5ff36f91da90f725776d00 is not affected by the bug 
>> before starting the bisect.
>>
>> Mathias
>>
>>
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>>
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