gmane.linux.newbie

kdump fails on encrypted root

Joseph D. Wagner — 2013-05-20T05:28:11

I can get kdump to work with encrypted root in kvm, but not on raw iron.

Can anyone help me figure out how to get it working?
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Excessive Swapping Under Minimal Load

Joseph D. Wagner — 2013-05-13T23:28:25

I am trying to use duplicity to backup my /home to an external hard 
drive
(usb 2 interface).  After running for a few minutes, my io slows to a 
crawl.
My system reports using about 300-400MB of swap, even though only about
600MB / 4GB is in use.

I am trying to isolate the cause.  It may be duplicity in conjunction 
with
the particulars of my configuration (see below).  I get good 
performance
under normal circumstances.  I am using fedora 18, which has /tmp 
mounted
using tmpfs, but duplicity never uses more than 1.0GB - 1.1GB.

First, is this the correct forum for asking for this kind of help?

Second, what information

The particulars of my configuration:
sda1 -> win7 hidden boot
sda2 -> win7 regular
sda3 -> grub2 boot
sda5 -> luks swap
sda6 -> luks ext4 root
sda7 -> regular ext4 data
sdb1 -> luks userdata1 -> md raid 0 with userdata1 & userdata2-> ext4 
home
sdc1 -> luks userdata2 -> md raid 0 with userdata1 & userdata2-> ext4 
home

My thinking in putting md raid on top of luks was that I would be able 
to
better use multithreading (2 luks, 1 per physical drive), whereas 
putting
luks on top of md raid might create a choke point (1 luks for 1 virtual
drive).  I'll admit that this might be the problem.  However, it works 
fine
under normal circumstances.

I was hoping someone could help me either 1) isolate what is causing 
the
swapping, or 2) tell me what is wrong with my configuration based upon 
their
knowledge of how the kernel works.

Thanks in advance.

Joseph D. Wagner
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GET BACK TO ME

Denis Wilfred — 2013-05-08T11:59:05

RE: UN COMPENSATION GRANT
VALUE: US$500,000.00
VALIDATION NO: UN/CG/IMF/WB/TD/013C

The United Nations through our monitoring works uncovered that you
have sent so much with Western Union, Money gram, Bank to Bank
Transfers in the pursuit of your Contract - Inheritance Project,
Lotto/Lottery(s). As a result we have resolved at aiding you with the
sum of US$500,000.00 to enable patch up with your life again.

As a result, you are required to fill out the followings:

1: FULL NAME:
2: HOUSE ADDRESS :
3: MOBILE/CELL PHONE NUMBER:
4: MODE OF PAYMENT:
5. OCCUPATION:
6. DATE OF BIRTH:
7. MARITAL STATUS;
8. NUMBER OF CHILDREN:

Let me hear from you immediately you have received this mail. Reply me
on (vdwilfred< at >gmail.com)

Yours faithfully,
Denis Wilfred
Coordinator
UN Compensation Grant Agency
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Re: A spinlock_irqsave question

Ryan — 2013-05-03T06:45:23

Hi Mario,
   Thanks for your inputs. I understood the diabling the irq on the
local CPU by spinlock_irqsave function.

   Can you also explain why should someone use spinlock_irqsave
instead of spinlock call.
   Why someone would want to also disable interrupts while holding a spinlock.

   One situation i can think of is as using spinlock_irqsave inside an
interrupt handler. Is this correct.
   But i also read that when one interrupt handler is being processed
- Linux will mask the same interrupt handler from being called again
until the current one has finished processing.
   that is  - Until the processing of interrupt handler is complete.
Linux will disable the future interrupts of the same type.
   In that case why should be disable interrupts by calling (
spinlock_irqsave) and use only spin_lock call alone.


Thanks


On Tue, Apr 30, 2013 at 2:24 PM, Mario Smarduch
<mario.smarduch< at >huawei.com> wrote:
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Re: Need help to measure and tune the latency in Linux RT

Ashoka K — 2013-04-30T13:17:05

Thanks for all the replies.
I am stuck with this issue for more tan a month. Explained this in
more detail at:

http://stackoverflow.com/questions/15805231/need-to-improve-the-linux-performance-for-embedded-system

But with no response from anyone.

I use PREEMPT patch for 2.6.33 vanilla kernel.

I have pasted all the processes running on my system:

  PID USER       VSZ STAT COMMAND
    1 root      3192 S    init
    2 root         0 SW   [kthreadd]
    3 root         0 SW   [ksoftirqd/0]
    4 root         0 SW   [events/0]
    5 root         0 SW   [khelper]
    8 root         0 SW   [async/mgr]
   84 root         0 SW   [sync_supers]
   86 root         0 SW   [bdi-default]
   88 root         0 SW   [kblockd/0]
   91 root         0 SW   [omap2_mcspi]
  116 root         0 SW   [rpciod/0]
  123 root         0 SW   [kswapd0]
  124 root         0 SW   [aio/0]
  125 root         0 SW   [nfsiod]
  126 root         0 SW<  [kslowd001]
  127 root         0 SW<  [kslowd000]
  128 root         0 SW   [crypto/0]
  267 root         0 SW   [mtdblockd]
  351 root         0 SWN  [jffs2_gcd_mtd8]
  359 root      3192 S    /sbin/syslogd
  361 root      3192 S    /usr/sbin/telnetd
  364 root      1996 S    vsftpd
  410 root     43844 S   my_appl
  416 root     56412 S <  my_appl
  417 root     84804 S    my_appl
  418 root     43844 S    my_appl
  419 root     84824 S    my_appl
  430 root     46552 S <  my_appl

The process my_appl is my application processes.

the ksoftirq is running with SCHED_OTHER.

$ chrt -p 3
pid 3's current scheduling policy: SCHED_OTHER
pid 3's current scheduling priority: 0

I will test by changing ksoftirq priority to see how it works.

Regards
Ashoka.  K


On Tue, Apr 30, 2013 at 5:43 PM, Stanislav Meduna <stano< at >meduna.org> wrote:
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Re: Need help to measure and tune the latency in Linux RT

ddegraff — 2013-04-30T12:02:16

On 04/30/2013 03:27 AM, Ashoka K wrote:

A project I am working on is using the same vintage kernel with RT 
patches applied, though on DaVinci (omap l138).

I, myself, however, have not dealt with any of that work, but I will ask 
the other developer if he has any suggestions.



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Re: Need help to measure and tune the latency in Linux RT

Jason Cooper — 2013-04-30T11:10:21

Ashoka,

linux-embedded is pretty quiet.  I'm not even sure why I'm still
subscribed to it.  You'll have better luck with your question by asking
on linux-arm-kernel (added to the cc).  I believe there is also a
linux-rt-users mailinglist [1].  A few comments below:

On Tue, Apr 30, 2013 at 01:57:21PM +0530, Ashoka K wrote:

Wow, this is ancient.  Is this a vanilla kernel?  If it's a vendor
kernel, you'll need to ask the vendor.


I'm not the guy to answer this ;-)  I'll just forward to the appropriate
lists.

hth,

Jason.

[1] http://vger.kernel.org/vger-lists.html#linux-rt-users
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Re: A spinlock_irqsave question

Mario Smarduch — 2013-04-30T08:54:05

I don't understand (a), in SMP you may disable IRQs on a CPU
(via *_irqsave()) but other CPUs may continue to receive interrupts.
The CPU load has nothing to do with blocking IRQs (on vanilla kernel)
To disable device IRQ you must disable it at the interrupt controller
level like disable_irq().
 

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Need help to measure and tune the latency in Linux RT

Ashoka K — 2013-04-30T08:27:21

Hi,

I have an embedded system running 2.6.33 cross compiled for ARM OMAP
with 1 GHZ uni-processor system.

The application has many threads and processes (around 15 total). In
that 1 thread is time critical and must run every interval confiurable
as 2, 4 or 8 milli sec etc. There is another thread which transfers
Images to a FTP or to HMI etc, whoever requested the image.
With this image transfer enabled my critical process misses the
deadline and timesout. This critical thread is at RR priority 50. I
used a HR timer thread with RR pri 55 to wakeup the critical thread
every 1 milli sec to do the job.
If image transfer is enabled i see that real time thread misses deadlines.

All traffic is flowing on common ethernet connection. Does it affect
in any way ?

How to find out where the kernel is waiting or delaying to schedule
the critical thread even though it is at higher RR priority. How to
measure the latency ?

I am trying to use Oprofile tool, but got some error in cross
compiling. Doesn't these tools add their own latency to the original
problem ?

Any tools ? which one is better. Please provide your input on this.


Regards
Ashoka.  K
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Re: A spinlock_irqsave question

Ryan — 2013-04-29T09:21:00

On Mon, Apr 29, 2013 at 2:42 PM, Mario Smarduch
<mario.smarduch< at >huawei.com> wrote:

You mean to say that
      a) Device IRQ can be taken care of some other core of the Same CPU?
      b) If the CPU Load is Less. then only one core will be active.
In that case - The device irq will be blocked?



This also include device irqs right? Apart from device irqs (touch
screen and so on).
what other irqs can be there. So what about mdelay(1000) in the above?
does that effect performance.

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Re: A spinlock_irqsave question

Mario Smarduch — 2013-04-29T09:12:33

spin_lock_irqsave(lock,flags)/ affects the running
CPU, it does not disable any device IRQ. Device
interrupts may be taken by other CPUs. There is a whole
other set of calls that deal with individual IRQs.


Yes, but much shorter then mdelay(1000)

spin_lock_irqsave()disables interrupts on the CPU it's issued.




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A spinlock_irqsave question

Ryan — 2013-04-29T08:30:48

Hi,

I have a question on spinlock_irqsave api. Am not sure if this is the
right place to ask.
Any help is highly appreciated.


let me know if my understanding is correct?



spinlock_irqsave()  <== Disables the IRQ?

                            <== No IRQs (that means no KB
interrupt,Interrupts from touch screen... etc..)



spinlock_irqrestore()


Is my understanding correct?
So the "time spend between spinlock_irqsave and spinlock_restore
should be very short?

For example there should not be something like this? Am i correct?


spinlock_irqsave()

mdelay(1000);


spinlock_irqrestore()




Also, what is meant by "spinlock_irqsave" disabled irq locally?


What is locally here?




Thanks,
Ryan
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Re: How could I record the information when kernel panic.

disnoir — 2013-04-27T04:02:49

Thank you for your reply.
I use ttyUSB0 to record the dmesg, cause this is a notebook 
(asus-k42je), which has no serial port, so I use a 
serial-port-to-USB-convertor.
I found that if I add console=ttyUSB0,115200n8 to kernel parameter, the 
kernel will fail to boot, and also without any information.
so I get into system on normal configuration (without console=...), and 
modify rsyslog.conf to log kernel info to /dev/ttyUSB0.
That works, use another pc to watch that serial port, all the 
information in dmesg will show in that serial port either.
But, when I test that if will also work during the kernel-panic ( I try 
"echo c > /proc/sysrq-trigger" ), nothing record into serial.
I guess kernel crash will cause rsyslogd no working.
So I use kdump-tools, kexec-tools to record a kernel dump, and this 
could work even on kernel-panic.
Now, I just need to wait the problem happen again.

:-)

disnoir
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Re: How could I record the information when kernel panic.

Brandon Philips — 2013-04-26T17:33:22

Your best bet is to use one of the following:
0) Use sysrq to investigate a bit:
https://www.kernel.org/doc/Documentation/sysrq.txt
1) Hook a serial console up if your system has one to another system
with a null modem cable and console=ttyS0,<baud> passed in to the
kernel at boot
2) Try netconsole if you don't have a serial console:
https://www.kernel.org/doc/Documentation/networking/netconsole.txt

I would recommend trying a newer kernel and see if your bug is fixed.
If it is you could bisect down to the commit that fixes it and let the
debian kernel maintainers know.

Good luck,

Brandon
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How could I record the information when kernel panic.

disnoir — 2013-04-24T17:18:24

There is a random probability that cause the kernel panic (debian with 
kernel 3.2.41), when I execute:
"sudo umount /media/data /media/big".

Things are like this:

I use "udisks --mount /dev/sda3" to mount "data" which is a ntfs filesystem.
similarly, I use "udisks --mount /dev/wd5000bpvt/big" to mount "big" 
which is a ext4 filesystem.

After finish using these filesystems, I use "sudo umount /media/data 
/media/big" to umount the filesystems, and the hole system just suddenly 
halt (mouse is not moving).

using alt-sysrq-b to reboot the system. nothing record in the 
/var/log/messages.

So, How could I record the kernel error/info, when system was halt ?

Thanks a lot!


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how does ld.so transfer execution to executable section ?

ishare — 2013-04-06T13:46:47

  At boot stage ,the process 1 will execute '/bin/sh' . as it needs ld.so to help loading other .so ,
  it loads ld.so into memory and execute ld.so first .

  My question is when and how does ld.so transfer its execution to code of /bin/sh ?

  Thanks!
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mapping memory reserved by "memmap" kernel boot param into user space

Jayram Déshpandé — 2013-04-01T05:11:56

Hello ,

As discussed in this[1] discussion, i am reserving a memory chunk at the
boot time using a kernel boot parameter memmap=8G$64G

I have written a character driver [2] kernel module which , during
initialization does a ioremap of this reserved memory chunk. As explained
here , in my driver mmap all i need to do is remap_pfn_range for this
memory chunk pointer returned by the ioremap.

I am running this on 3.x linux kernel. My user space application opens this
memory chunk as a device mounted by the driver. When i do mmap from the use
space application i see a system hang. my dmesg don't provide me much
information.

So questions are :

1 ) Does remap_pfn_range function have some upper limit on the size of the
memory that can be remaped to ? Note that i am trying to reserve a
comparatively large chunks of memory at the boot time of the order of 64GB
to about 150GB. The system can have 128 to 256 GB of ram.

2) I tried by disabling the ioremap from the initialization and thus
directly doing the page frame numbers remapping in the mmap ioctl routing.
But that also results in a hang.

3) I tried with a page-fault handler , but that doesn't seem to help either.

Regards,
-Jay

P.S. code can be found here [4]

[1] http:// stackoverflow.com/q/1911473/143897
[2] http:// pete.akeo.ie/2011/08/writing-linux-device-driver-for-kernels.html
[3] http:// www.
linuxquestions.org/questions/linux-kernel-70/mmap-of-several-gb-of-reserved-memory-using-805818/#post3972954
[4] http:// stackoverflow.com/questions/12790382/mapping-memory-reserved-by-mmap-kernel-boot-param-into-user-space
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Re: seq in tcp protocol

Anatoliy Sivov — 2013-03-30T19:17:50

I could be wrong, but I guess linux uses Minshall's modification of  
Nagle's algorithm.


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Re: can not find definition of ntohl

Anatoliy Sivov — 2013-03-30T17:10:51



I guess, ntohl was always defined as macro in  
include/linux/byteorder/generic.h
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init file for boot

ishare — 2013-03-30T09:11:13

  After kernel mount the real device to "/" , is the initramfs still  usefull ? If so ,it is mounted at which entry?

  At the end stage of boot , kernel will execute a init file , 
  whether this file locates at initramfs address space  *or*  the device mounted at "/" ?

  I feel confused  of  this point .
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Re: Mount two device on the same directory

Drew — 2013-03-30T02:04:58

My understanding is that whichever filesystem was mounted last, that
will be the one responding to ls.

For example, when you mount a usb stick to /mnt/mydevice, the
directory contents are replaced with the contenst of the usb stick you
mounted.

To see what I mean:

mkdir /mnt/mydrive
touch /mnt/mydrive/somefile
ls /mnt/mydrive/
mount /dev/(whatever the device is) /mnt/mydrive
ls /mnt/mydrive/

somefile should appear in the listing before mount but not after mounting.