August 2011 - kernelnewbies@kernelnewbies.org

How to find out if the NIC supports SR-IOV
by C K Kashyap Aug. 22, 2011

Aug. 22, 2011

Hi, I am working with a westemere based server. I need to find out if the NIC installed there supports SR-IOV - what would be the best way to determine that? Regards, Kashyap hwconfig ------------- Summary: HP DL160 G6, 2 x Xeon E5620 2.40GHz, 15.7GB / 16GB 1333MHz, 1 x 500GB SATA System: HP ProLiant DL160 G6, C-2N/16/500, ySPEC 25.0 Processors: 2 x Xeon E5620 2.40GHz (HT enabled, 8 cores, 16 threads) - Gulftown B1, 64-bit, quad-core, 32nm, L3: 12MB Memory: 15.7GB / 16GB 1333MHz == 4 x 4GB - 4GB PC3-10600 Hynix DDR3-1333 ECC Registered CL9 1Rx4 14 x empty Disk: sda (ahci0): 500GB (1%) JBOD == 1 x 500GB 7.2K SATA/300 HP/WD RE4 Disk-Control: ahci0: HP/Intel ICH10 82801J 6 Port SATA/300 AHCI Chipset: Intel 5520 IOH-36D B3 (Tylersburg), 82801JIR A0 (ICH10R) Network: eth0 (igb): HP NC362i/Intel 82576 Gigabit, 1Gb/s <full-duplex> Network: eth1 (igb): HP NC362i/Intel 82576 Gigabit, no carrier OS: YLinux 5.4.3, RHEL Server 5.4, Linux 2.6.18-164.2.1.el5 x86_64, 64-bit BIOS: HP O33 08/16/2010, rev 8.15 lspci shows this - 05:00.0 Ethernet controller: Intel Corporation 82576 Gigabit Network Connection (rev 01) Subsystem: Hewlett-Packard Company NC362i Integrated Dual port Gigabit Server Adapter Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr+ Stepping- SERR+ FastB2B- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- Latency: 0, Cache Line Size: 256 bytes Interrupt: pin A routed to IRQ 82 Region 0: Memory at fbe60000 (32-bit, non-prefetchable) [size=128K] Region 1: Memory at fbe40000 (32-bit, non-prefetchable) [size=128K] Region 2: I/O ports at e880 [size=32] Region 3: Memory at fbeb8000 (32-bit, non-prefetchable) [size=16K] Expansion ROM at fbe20000 [disabled] [size=128K] Capabilities: [40] Power Management version 3 Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold+) Status: D0 PME-Enable- DSel=0 DScale=1 PME- Capabilities: [50] Message Signalled Interrupts: 64bit+ Queue=0/0 Enable- Address: 0000000000000000 Data: 0000 Capabilities: [70] MSI-X: Enable+ Mask- TabSize=10 Vector table: BAR=3 offset=00000000 PBA: BAR=3 offset=00002000 Capabilities: [a0] Express Endpoint IRQ 0 Device: Supported: MaxPayload 512 bytes, PhantFunc 0, ExtTag- Device: Latency L0s <512ns, L1 <64us Device: AtnBtn- AtnInd- PwrInd- Device: Errors: Correctable- Non-Fatal+ Fatal+ Unsupported- Device: RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+ Device: MaxPayload 256 bytes, MaxReadReq 4096 bytes Link: Supported Speed 2.5Gb/s, Width x4, ASPM L0s L1, Port 2 Link: Latency L0s <4us, L1 <64us

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How to get the physical address of memory allocated by kmalloc
by subin gangadharan Aug. 22, 2011

Aug. 22, 2011

Hi All, Is there any API exists in kernel to get the physical address of the memory allocated by kmalloc.Can I use virt_to_phys for this ? With Regards Subin Gangadharan Everything should be made as simple as possible,but not simpler.

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Reading debug/tracing info
by Prateek Sharma Aug. 21, 2011

Aug. 21, 2011

Hello all, I am learning how to add static trace points via trace_events. I am seeing the trace using 'cat /sys/kernel/debug/tracing/trace' . Naturally the tracing buffer size is limited. My question is, what is the recommended way of reading trace data? Ive looked at perf record/report, but so far, i have only managed to get aggregated statistics, or complete dumps. What i need is just a way to collect all the trace output to one file. Basically i am using the trace events as a souped up printk (since i need to collect large amounts of traces). Do i need to use LTTng/viewer or something for this task? Thanks!

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getting started
by Littlefield, Tyler Aug. 20, 2011

Aug. 20, 2011

Hello all: I'd like to get going working on the kernel (I've tried getting started the last few times). On the kernelnewbies page, one of the kernel janitor projects is to balance out functions and clean up code. I'm curious if there would be someone, or a group of someone's who would mind assigning me a specific file or a small driver of some sort that needs this so I can get started helping out? -- Take care, Ty my website: http://tds-solutions.net my blog: http://tds-solutions.net/blog skype: st8amnd127 My programs don't have bugs; they're randomly added features!

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books and pointers...
by Srinidhi Rao Aug. 20, 2011

Aug. 20, 2011

Hello Kernel Hackers, As you can notice I am a kernel newbee!, I believe this is the platform to ask any thing about the Linux kernel. Well, I am extremely interested to know more about kernel programming especially in the networks and the PCI subsystems, I reall want to know where and how to start, I have some basic knowledge of IPC and I want to build on this... Kindly guide me with our valuable pointers to start with. -- 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.

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Port Linux multiprocessor support
by Giorgis Georgakoudis Aug. 20, 2011

Aug. 20, 2011

Hello all, I would like to ask for some pointers regarding porting Linux kernel multiprocessor support in new platforms. More specifically, what are the HW requirements that a platform must have to enable Linux multiprocessing and some info on kernel internals with respect to the booting process, scheduling/migration etc. I've been looking around for relevant documenta- tion but found little to none. Best regards, Giorgis

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How to measure the performance hit of changes in kernel code
by john k Aug. 20, 2011

Aug. 20, 2011

What is the optimal way to measure the performance hit a change in the kernel brings to the system under normal conditions? Are there tools for this job or a standard procedure kernel developers follow or everyone comes up with his own metrics? I know it sounds vague and maybe the measurement must be related with where the change is on the kernel code. Say for example that I implemented some extra security checks in the copy_from_user function, or some other critical code. Whats the best way to measure the performance hit it causes? I have used measurements of the time a full kernel compile takes, but I dont think this is the best metric. Also, is there a test suite that somehow emulates actions of an average user or another for an average web server? So that you can take average measurements etc (In trying to establish an overall performance hit, so that the metric may be unrelated to the part of the kernel code that is affected)

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multiple dependent out-of-tree modules
by Jorgyano Bruno Aug. 20, 2011

Aug. 20, 2011

Hello guys! I'm working with three out-of-tree kernel modules, one of them export symbols used by the others. At compile time, MODPOST warns about undefined symbols, which are defined on the first module and used in the second and third modules. When I try to load the modules* "insmod" *returns the error "Unknown Symbol in module" for those symbols warned by MODPOST. How can I to compile several out-of-tree modules which depends on one another and make to the dependant modules look for the needed symbols on the directories of the modules which have the symbols? I have found a similar question here http://www.spinics.net/lists/newbies/msg22926.html, but unanswered. ------------------------- Jorgyano

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Re: ohci_hcd leak ed
by DiP Aug. 19, 2011

Aug. 19, 2011

I found where it is. It seems to appear on my desktop box when I connect cams to the same bus. Two connectors next to each other. But on the notebook it does matter. Any bus, any port. Problem still alive with a kernel 3.0.2-pf-di #1 SMP PREEMPT Fri Aug 19 00:21:22 EEST 2011 x86_64 Intel(R) Core(TM)2 Duo CPU E8200 @ 2.66GHz GenuineIntel GNU/Linux //D

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Is it possible to relocate a kernel page in physical memory?
by Arvid Brodin Aug. 19, 2011

Aug. 19, 2011

I want to do memory checks (à la memtest86) on a running system. I know using ECC memory would be a better approach, but unfortunately that is not an option in this case. Also, this seems like an excellent opportunity to learn more about the memory system in Linux. This is on a AVR32 embedded system, BTW. One approach is to use the AVR32's built-in SRAM pages to store and run kernel code that periodically takes a spinlock and checks a small part of the physical memory, before writing back its original value. This has numerous problems, among others that the SRAM pages are also used by the power management code on these processors. And of course, it's not exactly portable... Another approach is to run the test as a part of the normal kernel. For memory allocated by user processes, this should be pretty straight-forward (I think): just copy the page data to another physical page and modify the page tables (right?). When in comes to the kernel, I might be able to skip testing of the (read-only) text segment by doing md5summing over it instead (would this have any drawbacks)? But how would one test writable pages allocated by the kernel? Is there a way to "relocate" a kernel page in physical memory? -- Arvid Brodin Enea Services Stockholm AB

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