* Re: [PATCH net-next] scm: optimize put_cmsg()
[not found] ` <20210416105735.073466b3@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
@ 2021-04-25 19:59 ` Naresh Kamboju
2021-04-25 21:22 ` Eric Dumazet
0 siblings, 1 reply; 2+ messages in thread
From: Naresh Kamboju @ 2021-04-25 19:59 UTC (permalink / raw)
To: Eric Dumazet
Cc: David S . Miller, Jakub Kicinski, netdev, Eric Dumazet,
Soheil Hassas Yeganeh, lkft-triage, Linux-Next Mailing List
Hi Eric,
On Fri, 16 Apr 2021 at 23:27, Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Thu, 15 Apr 2021 10:37:53 -0700 Eric Dumazet wrote:
> > From: Eric Dumazet <edumazet@google.com>
> >
> > Calling two copy_to_user() for very small regions has very high overhead.
> >
> > Switch to inlined unsafe_put_user() to save one stac/clac sequence,
> > and avoid copy_to_user().
> >
> > Signed-off-by: Eric Dumazet <edumazet@google.com>
> > Cc: Soheil Hassas Yeganeh <soheil@google.com>
>
> Hi Eric!
>
> This appears to break boot on my systems.
I have been noticing this problem.
>
> IDK how exactly, looks like systemd gets stuck waiting for nondescript
> services to start in initramfs. I have lots of debug enabled and didn't
> spot anything of note in kernel logs.
We (LKFT) are still seeing this problem only on arm architecture on
next-20210416 tag onwards. our bisect script points to this commit.
Steps to reproduce:
- build linux next latest next-20210423 tag with below config
- kernel-config:
https://builds.tuxbuild.com/1reqrnNLnHEX9uEZFngRfaoJa9E/config
- boot qemu-arm with below command
- /usr/bin/qemu-system-aarch64 -cpu host,aarch64=off -machine
virt-2.10,accel=kvm -nographic -net
nic,model=virtio,macaddr=BA:DD:AD:CC:09:04 -net tap -m 2048 -monitor
none -kernel zImage --append "console=ttyAMA0 root=/dev/vda rw" -hda
rpb-console-image-lkft-am57xx-evm-20201022181203-3085.rootfs.ext4 -m
4096 -smp 2 -nographic
- After the mount rootfs - the systemd gets stuck
>
> I'll try to poke at this more, but LMK if you have any ideas. The
> commit looks "obviously correct" :S
May I request to investigate this on arm architecture.
The qemu_arm boot failed link,
https://lkft.validation.linaro.org/scheduler/job/2565371#L540
The qemu_arm boot pass after the reverting this patch,
commit 38ebcf5096a86762b82262e96b2c8b170fe79040
scm: optimize put_cmsg()
on the latest linux next tags i have to revert two commits.
"scm: fix a typo in put_cmsg()"
"scm: optimize put_cmsg()"
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
--
Linaro LKFT
https://lkft.linaro.org
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH net-next] scm: optimize put_cmsg()
2021-04-25 19:59 ` [PATCH net-next] scm: optimize put_cmsg() Naresh Kamboju
@ 2021-04-25 21:22 ` Eric Dumazet
0 siblings, 0 replies; 2+ messages in thread
From: Eric Dumazet @ 2021-04-25 21:22 UTC (permalink / raw)
To: Naresh Kamboju
Cc: Eric Dumazet, David S . Miller, Jakub Kicinski, netdev,
Soheil Hassas Yeganeh, lkft-triage, Linux-Next Mailing List
On Sun, Apr 25, 2021 at 9:59 PM Naresh Kamboju
<naresh.kamboju@linaro.org> wrote:
>
> Hi Eric,
>
> On Fri, 16 Apr 2021 at 23:27, Jakub Kicinski <kuba@kernel.org> wrote:
> >
> > On Thu, 15 Apr 2021 10:37:53 -0700 Eric Dumazet wrote:
> > > From: Eric Dumazet <edumazet@google.com>
> > >
> > > Calling two copy_to_user() for very small regions has very high overhead.
> > >
> > > Switch to inlined unsafe_put_user() to save one stac/clac sequence,
> > > and avoid copy_to_user().
> > >
> > > Signed-off-by: Eric Dumazet <edumazet@google.com>
> > > Cc: Soheil Hassas Yeganeh <soheil@google.com>
> >
> > Hi Eric!
> >
> > This appears to break boot on my systems.
>
> I have been noticing this problem.
>
> >
> > IDK how exactly, looks like systemd gets stuck waiting for nondescript
> > services to start in initramfs. I have lots of debug enabled and didn't
> > spot anything of note in kernel logs.
>
> We (LKFT) are still seeing this problem only on arm architecture on
> next-20210416 tag onwards. our bisect script points to this commit.
>
> Steps to reproduce:
> - build linux next latest next-20210423 tag with below config
> - kernel-config:
> https://builds.tuxbuild.com/1reqrnNLnHEX9uEZFngRfaoJa9E/config
> - boot qemu-arm with below command
> - /usr/bin/qemu-system-aarch64 -cpu host,aarch64=off -machine
> virt-2.10,accel=kvm -nographic -net
> nic,model=virtio,macaddr=BA:DD:AD:CC:09:04 -net tap -m 2048 -monitor
> none -kernel zImage --append "console=ttyAMA0 root=/dev/vda rw" -hda
> rpb-console-image-lkft-am57xx-evm-20201022181203-3085.rootfs.ext4 -m
> 4096 -smp 2 -nographic
>
> - After the mount rootfs - the systemd gets stuck
>
> >
> > I'll try to poke at this more, but LMK if you have any ideas. The
> > commit looks "obviously correct" :S
>
> May I request to investigate this on arm architecture.
> The qemu_arm boot failed link,
> https://lkft.validation.linaro.org/scheduler/job/2565371#L540
>
> The qemu_arm boot pass after the reverting this patch,
> commit 38ebcf5096a86762b82262e96b2c8b170fe79040
> scm: optimize put_cmsg()
Well, as already reported, this patch had an obvious typo.
Fixed later by "scm: fix a typo in put_cmsg()"
Can you trace put_cmsg() and check that systemd passes an aligned
control buffer ?
Kernel was indeed able to handle arbitrary alignment, but why the
application would
force slow copyout() (alignment mismatch between source/destination buffers)
is quite strange.
>
> on the latest linux next tags i have to revert two commits.
> "scm: fix a typo in put_cmsg()"
> "scm: optimize put_cmsg()"
>
> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
>
> --
> Linaro LKFT
> https://lkft.linaro.org
^ permalink raw reply [flat|nested] 2+ messages in thread
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[not found] ` <20210416105735.073466b3@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
2021-04-25 19:59 ` [PATCH net-next] scm: optimize put_cmsg() Naresh Kamboju
2021-04-25 21:22 ` Eric Dumazet
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