August 2011 - kernelnewbies@kernelnewbies.org

Soft interrupt in multi-core environment
by J.Hwan Kim Aug. 26, 2011

Aug. 26, 2011

Hi, everyone When network card interrupts occur in multi-core system, what core is used by soft irq for network interrupts? That is, for example, if the IRQ happens in core 0, does the soft irq run on the same core ? Is it possible for soft irq to use other core different from hard IRQ? Thanks in advance. Best Regards, J.Hwan Kim

2 1

How to distribute IRQs to all cores
by J.Hwan Kim Aug. 26, 2011

Aug. 26, 2011

Hi, everyone The interrupts of my ixgbevf driver occurs only Core 0 although the user space "irqbalance" serivce is working. How can I distribute the interrupt of RX in ixgbevf to all cores? Is there any kernel compile option for it ? cat /proc/interrupts | grep "isv" 97: 8 0 0 0 0 0 0 0 PCI-MSI-edge isv0-rx-0 99: 7 0 0 0 0 0 0 0 PCI-MSI-edge isv0:lsc 103: 2059 0 0 0 0 0 0 0 PCI-MSI-edge isv2-rx-0 104: 14 0 0 0 0 0 0 0 PCI-MSI-edge isv2-tx-0 105: 1 0 0 0 0 0 0 0 PCI-MSI-edge isv2:mbx "isv" is netdevice name of my ixgbevf. Thanks in advance. Best Regards, J.Hwan Kim

2 2

How to make the kernel support NTFS?
by Parmenides Aug. 25, 2011

Aug. 25, 2011

Hi, I have dumped a lfs 6.3 cdrom to a virutal hard disk in vmware, and it goes without any problem. The original kernel version of lfs 6.3 is 2.6.25. I have upgraded it to 2.6.34 and it seems work well. But, when trying to compile the kernnel 2.6.34 to include the NTFS support, the kernel can not boot and gives me the following messages: Root-NFS: No NFS server available, giving up. VFS: Unable to mount root fs via NFS, trying floppy. Kernel panic - not syncing: VFS Unable to mount root fs on unknown-block(2,0) When doing 'make menuconfig', I have selected these options: File systems -> FUSE(Filesystem in Userspace) support -> DOS/FAT/NT Filesystem -> NTFS file system support -> NTFS write support and all of them are compiled into the kernel, rather than kernel modules. The kermel parameter is also OK: default 0 timeout 30 title LFS root(hd0,0) kernel /boot/vmlinuz-2.6.34 root=/dev/hda1 Now that I just add NTFS support, what's the NFS matter? How can I make the kernel to support the NTFS file system?

4 8

Error Building Fedora Kernel - problem in applying patch
by Vaibhav Jain Aug. 24, 2011

Aug. 24, 2011

Hi, I am trying to build fedora 15 kernel (2.6.39) on a fedora 15 machine (2.6.38.8.-25.fc15.i686.PAE). I am following the document : http://fedoraproject.org/wiki/Building_a_custom_kernel I made a few changes to the source code (only prink statements) and generated a patch as given in the doc by the name * linux-2.6-my-new-patch.patch*. I added the following lines to the spec file at the appropriate places: *Patch 20005: linux-2.6-my-new-patch.patch* * ApplyPatch linux-2.6-my-new-patch.patch* But as soon as I build the kernel I get the error : *ERROR: Patch linux-2.6-my-new-patch.patch not listed as a source patch in spec file* *error: Bad exit status from /var/tmp/rpm-tmp/t07KDk (%prep)* ** *RPM build error: * * Bad exit status from /var/tmp/rpm-tmp/t07KDk (%prep)* I am doing everything according to the doc. Please let me know what could have gone wrong. Thanks Vaibhav Jain

2 2

Compile the driver against kernel source requires a build kernel ??
by Sraddha Aug. 24, 2011

Aug. 24, 2011

I am trying to build a led driver for the samsung kernel 2.6.35.7 I have 2.6.35-22-generic installed on my host machine Now I thought is I could take the header files for the 2.6.35.7 kernel from the net sudo apt-get install kernel-headers-2.6.35.7: Error:Unable to locate package kernel-headers-2.6.35.7 Any suggestion for the header files can I use the header files of 2.6.35 like if I type sudo apt-get install kernel-headers-2.6.35 and use these header files for the led driver compilation I have the samsung kernel source , so Maybe I just compile the led driver against this source without compiling the entire samsung kernel . Plz iluminate . Regards Sraddha

2 1

Question on __pv_stub
by subin gangadharan Aug. 24, 2011

Aug. 24, 2011

Hi All, I am just trying to understand __va macro. I can see two definitions,one in include/asm-generic/page.h and other is in arch/arm/include/asm/memory.h. The first definition is just adding PAGE_OFFSET,but the second one boil downs to __pv_stub.Could anybody please help me to understand what this __pv_stub for? With Regards Subin Gangadharan Everything should be made as simple as possible,but not simpler.

1 0

What does drop_caches do?
by Prateek Sharma Aug. 24, 2011

Aug. 24, 2011

Hello everyone, I've been trying to understand the role of the pagecache, starting with drop_caches and observing what it does. From my understanding of the code (fs/drop_caches.c) , it walks over all the open files/inodes, and invalidates all the mapped pages. Pages which are *not* dropped are either dirty,in-use,anonymous,mapped(to pagetable),or writeback) . Is my understanding correct? But, when i run drop_caches, there are still some pages which show up as cached. Why arent all cache pages getting dropped ? My confusion runs much deeper. What exactly constitutes the pagecache? All filebacked pages ? mmaped files ? If i copy a bunch of files, why does my cache get polluted with those pages? Thanks for reading. I'd be grateful if someone can enlighten me about some pagecache internals . (Please keep me CC'ed) <begin experiment> root@tripitz:/etc/apt# free -m total used free shared buffers cached Mem: 1995 1854 140 0 79 700 -/+ buffers/cache: 1074 920 Swap: 4767 762 4005 root@tripitz:/etc/apt# echo 3 > /proc/sys/vm/drop_caches root@tripitz:/etc/apt# free -m total used free shared buffers cached Mem: 1995 1373 621 0 0 363 -/+ buffers/cache: 1009 985 Swap: 4767 762 4005 <end experiment>

3 2

startingKernelProgramming
by Srinidhi Rao Aug. 24, 2011

Aug. 24, 2011

Hi all, I am in the initial hard steps of learning the nuances of kernel programming, as to begin what are all the modules (header files) to use its data-structures be included to go about, as I tried this source: src: http://tldp.org/LDP/lkmpg/2.6/html/x121.html /* * hello-1.c - The simplest kernel module. */ #include <linux/module.h> /* Needed by all modules */ #include <linux/kernel.h> /* Needed for KERN_INFO */ int init_module(void) { printk(KERN_INFO "Hello world 1.\n"); /* * A non 0 return means init_module failed; module can't be loaded. */ return 0; } void cleanup_module(void) { printk(KERN_INFO "Goodbye\n"); } as compilation followed this: box@x86:~$ cc kernel_hello.c kernel_hello.c:3: fatal error: linux/module.h: No such file or directory compilation terminated. -- Thanks and Regards, Srinidhi. ---- All our knowledge has its origins in our perception. -- Leonardo da Vinci. ---- Tell me and I forget. Teach me and I remember. Involve me and I learn. -- Benjamin Franklin.

2 1

where is the definition of irq_desc array?
by LovelyLich Aug. 24, 2011

Aug. 24, 2011

Hi all, First, I have to say sorry for my pool English , because I am not a native English speaker. I know this is too simple, but I have tried hours to get the definition (not declaration) of irq_desc array in the interrupt subsys. Actually, I have been troubled in finding the definition. Because the array name( irq_desc) is same as the name of struct irq_desc. I think the irq_desc array is the core of interrupt subsys, so I didn't describe it in details. I tried describing my question , if there is something not clear, please let me know ,and I will try .. Sorry for my pool English again....

2 1

question about staging tree branches
by Prashant Shah Aug. 23, 2011

Aug. 23, 2011

Hi, There are 4 branches in the staging tree remotes/staging/master remotes/staging/ralink remotes/staging/staging-linus remotes/staging/staging-next Is the staging-linus is what Linus merges and staging-next is merged by linux-next tree ? What is ra-link for ? Regards.

3 3