- kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

kallsyms_lookup_name
by Venkatram Tummala Aug. 9, 2011

Aug. 9, 2011

Hi, I need to use some unexported kernel symbols in my kernel module but in the particular kernel version i am based on (2.6.18 - RHEL 5.7), kallsyms_lookup_name is not exported and there is no kallsyms_on_each_symbol in this kernel. And I can't change the kernel owing to reasons i have no control over. In this scenario, how do i use unexported symbols. Is there any other mechanism by which i can lookup the address of a kernel symbol. Thanks. Venkatram

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new kernel boot
by Amirali Shambayati Aug. 8, 2011

Aug. 8, 2011

Hi all, I successfully installed new kernel but as new kernel is going to boot, I receive this error: FATAL:could not load /lib/modules/2.6.32.43kerneltest/modules.dep : No such file or directory I checked /lib/modules/2.6.32.43kerneltest directory, and modules.dep exists! Any guidance how can I solve the problem? Thanks in advance, -- Amirali Shambayati Bachelor Student Computer Engineering Department Sharif University of Technology Tehran, Iran

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xx_initcall ( ) in kernel
by sumeet linux Aug. 8, 2011

Aug. 8, 2011

Dear friends, I want to know the basics xx_initcall ( ) in linux kernel. How this function works ? Observed in kernel code, many places late_initcall ( ), early_initcall ( ), arch_initcall ( ), core_initcall ( ) gets called. When did all these functions gets call during kernel initialization ? I am more interested in what is the sequence of these functions gets called one after another. Thank you. Regards, Sumeet

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Creating sparse file on XFS and EXT3 has different results
by Ashish Sangwan Aug. 8, 2011

Aug. 8, 2011

I write 1 program to create sparse file which contains alternate empty blocks and data blocks. For example block1=empty, block2=data, block3=empty ..... #define BLOCK_SIZE 4096 void *buf; int main(int argc, char **argv) { buf=malloc(512); memset(buf,"a",512); int fd=0; int i; int sector_per_block=BLOCK_SIZE/512; int block_count=4; if(argc !=2 ){ printf("Wrong usage\n USAGE: program absolute_path_to_write\n"); _exit(-1); } fd=open(argv[1],O_RDWR | O_CREAT,0666); if(fd <= 0){ printf("file open failed\n"); _exit(0); } while(block_count > 0){ lseek(fd,BLOCK_SIZE,SEEK_CUR); block_count--; for(i=0;i<sector_per_block;i++) write(fd,buf,512); block_count--; } close(fd); return 0; } Suppose, I create a new_sparse_file using this above code. When I run this program, on ext3 FS with block size 4KB, ls -lh shows size of new_sparse_file as 16KB, while du -h shows 8 kb, which, I think is correct. On xfs, block size of 4kb, ls -lh shows 16KB but du -h shows 12kb. Why are there different kinds of behavior? If I increase the block_count to be written so that a 200MB file is created, on XFS du -h shows 187MB and on EXT3 it shows 101MB.

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Re: Creating sparse file on XFS and EXT3 has different results
by Greg Freemyer Aug. 8, 2011

Aug. 8, 2011

There are no "specs" as to how a sparse file is handled in response to writes. Sparse is mostly beneficial when the holes are very large. If an app really wants to have minimal on disk space, you should pre-allocate space with fallocate. You may even need to hole punch after the writes. Both xfs and ext4 support both fallocate and hole punching. (I don't know the userspace call to hole punch. I think its a relatively new feature for ext4.) Greg On Aug 4, 2011 10:16 PM, "Ashish Sangwan" <ashishsangwan2(a)gmail.com> wrote:

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MSI-edge in /proc/interrupts
by J.Hwan Kim Aug. 8, 2011

Aug. 8, 2011

Hi, everyone When I read /proc/interrupts, it displays interrupt type of my ethernet card with "MSI-edge". Does it mean MSI-X interrupt or MSI interrupt? I set to my ethernet driver operates with MSI-X interrupt. Thanks in advance. Best Regards, J.Hwan Kim

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Exact scenario to use __wait_on_bit() ?
by Indraneel Mukherjee Aug. 8, 2011

Aug. 8, 2011

I have a queue where processes queue up I/O. Driver must pick any one I/O request from the queue(based on some criteria), do the I/O and then wake up corresponding process. Problem: How to selectively wake up a particular process from the middle of the Wait Queue? Instead, can I use __wait_on_bit() for this scenario? TIA, Indro

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Question on Alignment requiremnet
by subin gangadharan Aug. 7, 2011

Aug. 7, 2011

Hi All, I have some doubts on the alignment requirement.It would be really helpful,if someone can shed some light on this. Why there are so many different types of alignment like 4 byte, 8 byte,16 byte ?.My exact question is, in a 32 bit machine(I assume processor reads data in 4 bytes),how 16 byte alignment makes different from 4 byte alignment ?.How this will influence the processor performance ?. - With Regards Subin Gangadharan Everything should be made as simple as possible,but not simpler.

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Re: Compile kernel for various times and problem of too long time consuming
by Amirali Shambayati Aug. 7, 2011

Aug. 7, 2011

Would you say how you rebuild kernel? On Sun, Aug 7, 2011 at 10:34 PM, Randy Dunlap <rdunlap(a)xenotime.net> wrote: > On Sun, 7 Aug 2011 21:39:12 +0430 Amirali Shambayati wrote: > >> Hi all, >> Since I want to evaluate performance improvements by changing just one >> file in kernel(noop-iosched) and compiling kernel is too much >> time-consuming, I want to know that if I compile kernel for more than >> one time, does it take similar time to first time? >> >> I use following commands. If I don't use "make-kpkg clean" for next >> times, does it just compile the files which have been modified or it >> compile whole kernel package again? >> >> make-kpkg clean >> fakeroot make-kpkg --initrd --append-to-version=-some-string-here >> kernel-image kernel-headers > > Since I never use make-kpkg, I can only tell you that when I modified > block/noop-iosched.c and rebuilt the kernel, here is what was rebuilt: > > GEN /lnx/src/NEXT/linux-next-20110805/X32/Makefile > CHK include/linux/version.h > Using /lnx/src/NEXT/linux-next-20110805 as source for kernel > CHK include/generated/utsrelease.h > CALL /lnx/src/NEXT/linux-next-20110805/scripts/checksyscalls.sh > CHK include/generated/compile.h > CHK kernel/config_data.h > CC block/noop-iosched.o > LD block/built-in.o > LD vmlinux.o > MODPOST vmlinux.o > GEN .version > CHK include/generated/compile.h > UPD include/generated/compile.h > CC init/version.o > LD init/built-in.o > LD .tmp_vmlinux1 > KSYM .tmp_kallsyms1.S > AS .tmp_kallsyms1.o > LD .tmp_vmlinux2 > KSYM .tmp_kallsyms2.S > AS .tmp_kallsyms2.o > LD vmlinux > SYSMAP System.map > SYSMAP .tmp_System.map > Building modules, stage 2. > VOFFSET arch/x86/boot/voffset.h > CC arch/x86/boot/version.o > OBJCOPY arch/x86/boot/compressed/vmlinux.bin > LZMA arch/x86/boot/compressed/vmlinux.bin.lzma > MODPOST 575 modules > MKPIGGY arch/x86/boot/compressed/piggy.S > AS arch/x86/boot/compressed/piggy.o > LD arch/x86/boot/compressed/vmlinux > ZOFFSET arch/x86/boot/zoffset.h > OBJCOPY arch/x86/boot/vmlinux.bin > AS arch/x86/boot/header.o > LD arch/x86/boot/setup.elf > OBJCOPY arch/x86/boot/setup.bin > BUILD arch/x86/boot/bzImage > Setup is 14972 bytes (padded to 15360 bytes). > System is 1287 kB > CRC 64ecf4d > Kernel: arch/x86/boot/bzImage is ready (#18) > > > so it's a minimal rebuild, not a full kernel rebuild. > > --- > ~Randy > *** Remember to use Documentation/SubmitChecklist when testing your code *** > -- Amirali Shambayati Bachelor Student Computer Engineering Department Sharif University of Technology Tehran, Iran

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Compile kernel for various times and problem of too long time consuming
by Amirali Shambayati Aug. 7, 2011

Aug. 7, 2011

Hi all, Since I want to evaluate performance improvements by changing just one file in kernel(noop-iosched) and compiling kernel is too much time-consuming, I want to know that if I compile kernel for more than one time, does it take similar time to first time? I use following commands. If I don't use "make-kpkg clean" for next times, does it just compile the files which have been modified or it compile whole kernel package again? make-kpkg clean fakeroot make-kpkg --initrd --append-to-version=-some-string-here kernel-image kernel-headers Thanks for your help in advance, -- Amirali Shambayati Bachelor Student Computer Engineering Department Sharif University of Technology Tehran, Iran

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