Running kmemleak without sysfs support

Running kmemleak without sysfs support

[Daniel Baluta]

Hello all,

Can I make any use of kmemcheck if I don't have sysfs
kernel support enabled?

thanks,
Daniel.

Running kmemleak without sysfs support

[Daniel Baluta]

> Can I make any use of kmemcheck if I don't have sysfs
> kernel support enabled?

s/kmemcheck/kmemleak :D

Running kmemleak without sysfs support

[Catalin Marinas]

On Thu, 2011-01-20 at 10:41 +0000, Daniel Baluta wrote:
> Can I make any use of kmemcheck if I don't have sysfs
> kernel support enabled?

Kmemleak can scan output the memory and report the number of leaked
objects but if you need to get additional information about the leaked
objects (like backtrace), you need debugfs enabled.

DEBUG_FS doesn't seem to be dependent on SYSFS but I never tried to
enable one without the other (you might be able to mount the DEBUG_FS
somewhere other than /sys/kernel/debug/).

-- 
Catalin

Running kmemleak without sysfs support

[Daniel Baluta]

On Thu, Jan 20, 2011 at 12:52 PM, Catalin Marinas
<catalin.marinas@arm.com> wrote:
> On Thu, 2011-01-20 at 10:41 +0000, Daniel Baluta wrote:
>> Can I make any use of kmemcheck if I don't have sysfs
>> kernel support enabled?
>
> Kmemleak can scan output the memory and report the number of leaked
> objects but if you need to get additional information about the leaked
> objects (like backtrace), you need debugfs enabled.

How is this reporting done?  It will appear in dmesg output?

> DEBUG_FS doesn't seem to be dependent on SYSFS but I never tried to
> enable one without the other (you might be able to mount the DEBUG_FS
> somewhere other than /sys/kernel/debug/).

I see. I was using 2.6.32 where it seems that debugfs depended on sysfs.
Decoupling was done some time later [1].

thanks,
Daniel.

[1] http://kerneltrap.org/mailarchive/linux-kernel/2010/8/5/4603446

Running kmemleak without sysfs support

[Catalin Marinas]

On Thu, 2011-01-20 at 12:33 +0000, Daniel Baluta wrote:
> On Thu, Jan 20, 2011 at 12:52 PM, Catalin Marinas
> <catalin.marinas@arm.com> wrote:
> > On Thu, 2011-01-20 at 10:41 +0000, Daniel Baluta wrote:
> >> Can I make any use of kmemcheck if I don't have sysfs
> >> kernel support enabled?
> >
> > Kmemleak can scan output the memory and report the number of leaked
> > objects but if you need to get additional information about the leaked
> > objects (like backtrace), you need debugfs enabled.
> 
> How is this reporting done?  It will appear in dmesg output?

Yes.

> > DEBUG_FS doesn't seem to be dependent on SYSFS but I never tried to
> > enable one without the other (you might be able to mount the DEBUG_FS
> > somewhere other than /sys/kernel/debug/).
> 
> I see. I was using 2.6.32 where it seems that debugfs depended on sysfs.
> Decoupling was done some time later [1].

Ah, I missed that. I'll change DEBUG_KMEMLEAK to always select DEBUG_FS
(currently only if SYSFS).

Thanks / multumesc :).

-- 
Catalin

Running kmemleak without sysfs support

[Greg KH]

On Thu, Jan 20, 2011 at 12:41:57PM +0200, Daniel Baluta wrote:
> Hello all,
> 
> Can I make any use of kmemcheck if I don't have sysfs
> kernel support enabled?

Why would you ever want to run a kernel without sysfs support?  If you
turn it off, you loose a _lot_ of functionality that you will need to
add back to your system in some other manner.

What, specifically, is wrong with sysfs that is solved by turning it
off?

thanks,

greg k-h

Running kmemleak without sysfs support

[Daniel Baluta]

On Thu, Jan 20, 2011 at 5:56 PM, Greg KH <greg@kroah.com> wrote:
> On Thu, Jan 20, 2011 at 12:41:57PM +0200, Daniel Baluta wrote:
>> Hello all,
>>
>> Can I make any use of kmemcheck if I don't have sysfs
>> kernel support enabled?
>
> Why would you ever want to run a kernel without sysfs support? ?If you
> turn it off, you loose a _lot_ of functionality that you will need to
> add back to your system in some other manner.

I totally agree with you. But we've done it to save memory.

> What, specifically, is wrong with sysfs that is solved by turning it
> off?

There's nothing wrong with sysfs. In fact, I like it!

thanks,
Daniel.

Running kmemleak without sysfs support

[Greg KH]

On Fri, Jan 21, 2011 at 11:26:43AM +0200, Daniel Baluta wrote:
> On Thu, Jan 20, 2011 at 5:56 PM, Greg KH <greg@kroah.com> wrote:
> > On Thu, Jan 20, 2011 at 12:41:57PM +0200, Daniel Baluta wrote:
> >> Hello all,
> >>
> >> Can I make any use of kmemcheck if I don't have sysfs
> >> kernel support enabled?
> >
> > Why would you ever want to run a kernel without sysfs support? ?If you
> > turn it off, you loose a _lot_ of functionality that you will need to
> > add back to your system in some other manner.
> 
> I totally agree with you. But we've done it to save memory.

Does it really save memory?  If so, how much and what is your budget for
memory?

Are you worried about swapable or non-swapable memory usage?

> > What, specifically, is wrong with sysfs that is solved by turning it
> > off?
> 
> There's nothing wrong with sysfs. In fact, I like it!

Then you should turn it back on, it will save you a whole lot of grief
in the end :)

good luck,

greg k-h