December 2014 - kernelnewbies@kernelnewbies.org

Learning Memory Management for linux
by Dean Michael Ancajas Dec. 3, 2014

Dec. 3, 2014

Hi Everyone, I am starting to learn linux memory managemet using Gorman's book. I think it would be great if I could participate in a project relating to MM. Would any of you guys know a link of the current projects relating to MM that I can join? There are some projects listed on the linux-mm website but I am not sure if they are still updated... Thanks.

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Huge difference in build sizes
by Raghavendra Dec. 3, 2014

Dec. 3, 2014

Hello all, I am using Ubuntu-12.04 which came with 3.2 kernel. Parallel to this, I've compiled and installed 3.12.1 kernel using the Ubuntu-3.2's configuration, and the compiler which came with the distro. I've noticed that there is a huge difference in the size of the .ko file between the Ubuntu's kernel and the kernel which I've compiled. Sample results are : $ du -sh usb-storage.ko It shows : 56K for the Ubuntu's 3.2 kernel 1.3M for the custom kernel that I've compiled I've tested the same thing for a simple hello world module : $ du -sh hello.ko It shows : 4.0k for the Ubuntu's 3.2 kernel 56k for the custom kernel that I've compiled What could be the reason for this huge amount of difference of storage space in spite of using the same config file and compiler? Thanks in advance. Raghavendra ------------------------------------------------------------------------------------------------------------------------------- [ C-DAC is on Social-Media too. Kindly follow us at: Facebook: https://www.facebook.com/CDACINDIA & Twitter: @cdacindia ] This e-mail is for the sole use of the intended recipient(s) and may contain confidential and privileged information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies and the original message. Any unauthorized review, use, disclosure, dissemination, forwarding, printing or copying of this email is strictly prohibited and appropriate legal action will be taken. -------------------------------------------------------------------------------------------------------------------------------

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Re: from WHERE platform driver's probe is called?
by subin gangadharan Dec. 2, 2014

Dec. 2, 2014

On Thu, Nov 27, 2014 at 1:00 AM, Sunil Shahu <sunil.rockon(a)yahoo.in> wrote: > Hi Daniel, > Thanks, dump_stack() is what I needed. > > Hi Subin, > Thanks for the snapshot. > > Also, I am attaching a graph for what I understood after following > dump_stack(). > > Please let me know if there is any issue with the flow. > > Thanks, > Sunil. > > > > On Saturday, 22 November 2014 9:04 AM, subin gangadharan > <subingangadharan(a)gmail.com> wrote: > > > Hi Sunil, > >>>I am still not able to locate from WHERE this probe function is called and >>> WHO calls it? > > I can try to give you a snapshot of the function call trace. But if > you really want to get in depth detail, as Greg said look at the code > driver/base. > > driver_register > ->bus_add_driver->driver_attach->__driver_attach->driver_probe_device->really_probe->drv->probe > > Basically when you register your platform driver, the platform > bus(platform_bus_type) will scan for the matching device. If you look > at the platform_bus_type structure you can find the match function > which does the matching of driver and device. Once it's found the > right device, it will attach the driver to the device.Look at the > function driver_attach. And if you look at the > platform_driver_register function, you can see that > "platform_drv_probe" function is assigned to driver.probe function. > And this probe function will finally call your registered platform > driver probe function. > > Hope this helps. > > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > Hi Sunil, Thanks for the nice detailed snap shot. Subin

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Possible error in debugfs/file.c
by land.ho87＠gmail.com Dec. 2, 2014

Dec. 2, 2014

I'm just reading the kernel source and came across this which doesn't look quite right to me: 616 size_t size = strlen(file->private_data); strlen is used here when the pointer points to type: 567 struct array_data { 568 void *array; 569 u32 elements; 570 }; I think line 616 should probably be something like: size_t size = file->private_data.elements*sizeof(u32); I think strlen would terminate incorrectly on any null byte, and is unnecessary since the data is already counted. Is this a legitimate criticism?

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Interested in Networking, Memory and Btrfs Subsystems
by nick Dec. 2, 2014

Dec. 2, 2014

Greetings Fellow Kernel Developers, I am wondering if anyone would mind mentoring me in any of the three areas listed in my subject message. Further more I understand if no one accepts this offer due to my bad rep. Finally, after wasting some many people's time I am starting to write good patches as people can see from the logs of LKML. :) Thanks for the Help, Nick

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Greg Kroah-Hartman is doing an AMA on reddit :
by Thomas Dec. 2, 2014

Dec. 2, 2014

I know Greg K.H. used this mailing list. Maybe not everybody frequent reddit intensively. Greg Kroah-Hartman is doing an Ask Me Anything on reddit : A chance to asked more personal questions. ;) http://fr.reddit.com/r/linux/comments/2ny1lz/im_greg_kroahhartman_linux_ker… Thomas

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ktime_get() equivalent from user space
by manty kuma Dec. 2, 2014

Dec. 2, 2014

Hi, I need to measure some timings in my system. At driver level, i am using ktime_get() to log the times. I need to map this to something of the same unit at user space. I checked /proc/uptime. This value also includes the suspend time which ktime_get() doesn't include. Hence this option is ruled out. Is there any other proc entry or any other source which is of same unit? Best Regards, manty

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The limit of kernel memory in 64bit system
by J.Hwan Kim Dec. 1, 2014

Dec. 1, 2014

Hi, everyone As far as I know, the kernel memory limit is 1GB in 32bit system. Is it also applicable to 64bit system? What's the limit of kernel memory in 64bit system? Thanks in advance Regards, J.Hwan Kim

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Debug Kernel Modules With KGDB
by Freeman Zhang Dec. 1, 2014

Dec. 1, 2014

Hi list, I've been trying to setup a debug environment for linux kernel(v3.4,Android,ARM) with kgdb. It worked fine untill I tried to use it to debug a module. Under the instruction from LDD, I add module debug info in gdb with command: add-symbol-file test-module.ko address LDD uses `cat /sys/module/test-module/sections/.text` to get the address where the module has been loaded. However, I got: 0x00000000 When I use `lsmod`, I got: test-module 15278 0 - Live 0x00000000 (O) Why nothing but 0x00000000 ?? So I have to do some research in kernel/module.c, and find out that struct module -> module_core = 0xbf000000. But when I try these in gdb: add-symbol-file test-module.ko 0xbf000000 break one_of_my_function I got: Cannot access memory at address 0xbf002350 :( Could somebody help? All the best! Freeman Zhang

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KGPU : any scope?
by Raghavendra Dec. 1, 2014

Dec. 1, 2014

Hello all, I was going through the concept of KGPU, which is a GPU computing framework for the Linux Kernel. I've read the white paper on it(can be found at http://www.cs.utah.edu/~wbsun/kgpu.pdf) and I am very much interested in this project, but what could be the scope of this(although, the paper mentions a few application areas like crypto, networking, fs, etc)? Does the kernel really require GPU's assistance? What is the scope of building kernel frameworks around it? Also the current framework is build using CUDA. I want to re-implement the same using OpenCL as it is supported by most of the GPUs. As per my perspective, I see a huge learning opportunity here. But, practically how fas is it useful? Any suggestions would be helpful. Thanks Raghavendra. ------------------------------------------------------------------------------------------------------------------------------- [ C-DAC is on Social-Media too. Kindly follow us at: Facebook: https://www.facebook.com/CDACINDIA & Twitter: @cdacindia ] This e-mail is for the sole use of the intended recipient(s) and may contain confidential and privileged information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies and the original message. Any unauthorized review, use, disclosure, dissemination, forwarding, printing or copying of this email is strictly prohibited and appropriate legal action will be taken. -------------------------------------------------------------------------------------------------------------------------------

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