May 2011 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Changes in block layer for IOScheduler Insertion selection
by mani Feb. 6, 2012

Feb. 6, 2012

Dear All, I am working on linux kernel 2.6.32.9 tegra NVIDIA board. I am getting ~8MBps speed of the Nand disk if i use hdparm hdparm -t /dev/mtdblock3 i made changes in block layer of kernel as below:- block/blk-core.c static inline void add_request(struct request_queue *q, struct request *req) { drive_stat_acct(req, 1); /* * elevator indicated where it wants this request to be * inserted at elevator_merge time */ __elv_add_request(q, req, ELEVATOR_INSERT_BACK, 0); //__elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0); } changed ELEVATOR_INSERT_SORT to ELEVATOR_INSERT_BACK it improves my NAND speed to 10MBps. I am using "noop" I/O scheduler. Will this change have any adverse effect in kernel ? or any other side effect as far as i am using only Nand no Hard disk. Thanks Mani

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Can i allocate 4GB virtual addresses (more than a certain limit) using vmalloc?
by sandeep kumar Aug. 22, 2011

Aug. 22, 2011

Hi all, The following link gives the memory map for the arm architecture. http://www.arm.linux.org.uk/developer/memory.txt I have the following doubts.. 1) Any chipset(based on arm) manufacturer(qualcom,samsung..) should follow the same memory map. Is it hardly constrained or can be changed? Where are this constraints are implemented in the kernel source tree? 2) while i was student, i read in OS concepts that, "Virtual memory gives an illusion to a process, that it has always a larger continuous address space (even more than RAM) available to it." So i thought i could allocate howmuch ever memory i want. But seeing the above link,i observed there is some limitation in the address space created by the vmalloc(). So i m now thinking that vmalloc has some limit. Please make me clear these things.... With regards, Sandeep Kumar Anantapalli,

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SRIO maintenance read hangs (mpc8548)
by shrikant hegde Aug. 4, 2011

Aug. 4, 2011

Hi all, I am working on srio; When i tried to send maintenance packet to switch it hangs. Symptom when i tried to read DIDCAR of switch,( i.e read 0x8000_0000 ), or HDIDLOCK (0x8000_0068 ), execution of code hangs; if i press break in code warrior its coming out with an error. register value dump EPWISR 0x80000000 -- physical or logical/transport error interrupt LTLEDCSR 0x08000000 -- illegal transaction decode, received request/response packet LTLCCCSR 0x82000000 Below are my system detail: Processor mpc8548 and Tsi578 switch. Processor is connected to switch on same board.I have written standalone code (no OS) to exercise srio, using code warrior. Processor side configurations Its configured to 1x, 2.5gbs, host. law and tlb are configured. 0x8000_0000 0x8FFF_FFFF maintenance window configured 0x8000_0000 0x8000_0FFF (4k) switch side configuration 1x,2.5gbs, swap disabled (configured during POR) Processor side link training bit is setting. Am I missing any configuration , in switch side or processor side ? Any pointer is very helpful. Forgive me if its a wrong forum to post srio queries. thanks shrikant -- View this message in context: http://old.nabble.com/SRIO-maintenance-read-hangs-%28mpc8548%29-tp30949266p… Sent from the kernelnewbies mailing list archive at Nabble.com.

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questions for Linus
by Mulyadi Santosa June 23, 2011

June 23, 2011

Hi Greg.. I came with these questions for Linus, hope you're kind enough to collect it and forward it to Linus in LinuxCon: 1. When will Linux 2.8.x start? and what are the plans regarding the development model? do we back in dual 2.4.x/2.5x era? personally I think that model is nice.... makes one really know which tree to follow when he needs stable one, or the devel one... 2. I saw task/process scheduler is one that under heavy concern lately, take a look on "200 line patch that does wonder" for example. I am thinking, we better really incorporate pluggable scheduler framework, that enable us to change scheduling core algorithm on the fly. What do you think? 3. I read somewhere that once Coverity helps Linux kernel developers found out unseen bugs using sophisticated static code analysis. Is that still happening now? Probably a good deal, squashing bugs in nowadays kernel's size is pretty hard, I could say.. that's all for now Greg...thanks in advance...hopefully it's still make it.. -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com

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Build scatterlist covering a process' text segment?
by Arvid Brodin June 17, 2011

June 17, 2011

Hi, How do I build a scatterlist covering the text segment of a process? I have found (struct task_struct).mm->start_code and ->end_code, that gives the address (in some - unknown to me - address space) of the text segment. Since my try to convert these addresses to an sglist: sg_init_one(&sg, task->mm->start_code, <length>); failed miserably, I'm guessing these addresses need to be converted to some address space compatible with sg_init_one()/sg_set_buf() before use? (I probably need to search for pages containing these addresses?) Thanks, Arvid Brodin Enea Services Stockholm AB

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Not able to see all the symbols in the output of "nm" command
by Madhavi Manchala June 10, 2011

June 10, 2011

Dear All, I build the OpenWRT image for my target device. I am able to see the "vmlinux" image in trunk/build_dir/linux-s3c2510/linux-2.6.36 directory where linux-s3c2510 indicates my target device. I am NOT able to see some of the function names (symbols), which I developed, in the output of the "nm" command for vmlinux image. Am I missing any thing while building the image for getting all the symbols into the image? I am NOT able to see all the function names which are defined in arch/arm/plat-samsung/include/uncompress.h file. Please let me know if I am missing any thing. Thanks for your suggestions / hints. Thanks and Regards, Madhavi M.

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Implementing RFC 6056
by Arjun S R June 2, 2011

June 2, 2011

Hi, I would like implement RFC 6506 in linux kernel. It seems no one has implemented it. Its mainly about Transport protocol port randomisation. The fixed order[sequence of predictable randomness] of allocation of ephemeral port to application on request can cause malicious users to hijack connections based on time spent by the tcp ip api in various states. I have read the standards and is willing to go forward. Please post comments. -- Arjun S R

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picking an ARM board with jtag for debugging
by Christopher Harvey June 1, 2011

June 1, 2011

I'm looking for an ARM board with a cortex a9 mpcore with a good solution for jtag debugging under linux. I have a beagle and a pandaboard sitting in front of me, but the beagle only has cortex a8 and the pandboard jtag situation looks pretty dismal. (You need to buy and download a lot of software). Cost really isn't an issue, (under 1000$) but good gdb support is critical. I need jtag specifically because kgdb doesn't start up soon enough for me. Anybody here doing ARM linux development with jtag? thanks, -Chris

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Disabling nagle algorithm
by C K Kashyap June 1, 2011

June 1, 2011

Hi, Is setting *net.ipv4.tcp_low_latency to 1 the right way of disabling nagle's algorithm?* *Regards,* *Kashyap*

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Check Kernel Memory Allocation
by Dev Null May 31, 2011

May 31, 2011

Hello, I wanted to know how much kernel and userspace memory is available on the Linux system during run-time either by some C code or some procfile. Do you know how to do that? Thanks, Dev

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