May 2013 - kernelnewbies@kernelnewbies.org - Kernelnewbies Mailing Lists

Couple of questions on OOM trace.
by Shraddha Kamat May 9, 2013

May 9, 2013

Here is the OOM trace header : Out of memory: Kill process 5374 (min_free_kbytes) score 944 or sacrifice child Killed process 5374 (min_free_kbytes) total-vm:30495360kB,anon-rss:20155328kB, file-rss:64kB min_free_kbytes invoked oom-killer: gfp_mask=0x200da, order=0, oom_score_adj=0 min_free_kbytes cpuset=/ mems_allowed=0 ------------------ I understand that in this case free pages has gone below min_pages(1). Couple of questions based on these 4 lines : (1) I googled a lot but I am not able to find the meaning of 'score 994' , anon-rss and file-rss ? (2) In my understanding gfp_mask is relevant here to know from which Zone the memory allocation was tried , but failed - right ? (3) What do order and oom_score_adj signify here ? Regards, Shraddha (1) http://dd.qc.ca/people.redhat.com/kernel/min_free_kbytes.html

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Documentation on device-mapper and friends
by Kumar Amit Mehta May 8, 2013

May 8, 2013

I'm looking for information on device-mapper, the kernel space utility for Logical Volume Management (LVM2). It seems that the relevant code resides under drivers/md and a lot of other information is under Documentation/device-mapper/ That's fine, but is there any other document that gives more finer details about the device-mapper. I've also recently subsribed to the device-mapper mailing list. -Amit

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current tty
by Hatte John May 8, 2013

May 8, 2013

Hi： As I know .the /dev/tty is the current task's tty , which is stored to current->tty , My question is when does this value is assgined to current->tty ? Thanks!

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Re: current tty
by Hatte John May 8, 2013

May 8, 2013

It is not the answer I wanted , I am saking in term of coding . 2013/5/8 Jun Hu <jhu_com(a)163.com> > you can get it by "tty" command, like the following: > > junwork:/proc/self/task/1874 # tty > /dev/pts/0 > > > - > ----Original Message----- > -- > --------------------------------------------------------- > Jun Hu > > DSE In Suse China. > ---------------------------------------------------------- > > > > To: kernelnewbies(a)kernelnewbies.org > Subject: current tty > Date: Wed, 8 May 2013 12:21:32 +0800 > > Hi： > > As I know .the /dev/tty is the current task's tty , which is stored > to current->tty , > My question is when does this value is assgined to current->tty ? > > > Thanks! > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > >

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RE: read PCI memory and config spyce through /dev/mem
by Warlich, Christof May 8, 2013

May 8, 2013

Jun Hu <jhu_com(a)163.com> wrote: > strace your application, like as: > ... It's the lseek that fails: Obviously, /dev/mem is not seekable. What really puzzles me is that dd _does_ work on /dev/mem when looking at ordinary RAM, but I'm reluctant to further debug why. But anyhow, as I think it may at times be also useful for others to have a simple tool that allows to read (and write!) PCI memory, I share the few lines of code that I wrote to fulfill my needs. I hope that the included "documentation" is verbose enough. And I'm certainly interested if anyone finds bugs :-): #include <unistd.h> #include <stdio.h> #include <fcntl.h> #include <stdlib.h> #include <stdint.h> #include <assert.h> #include <sys/mman.h> void usage(const char *name) { fprintf(stderr, "Usage: %s address access [size]\033[2m\n", name); fprintf(stderr, " Either - prints \"size\" bytes \033[1mfrom\033[2m physical memory,\n"); fprintf(stderr, " starting at \"address\" and using \"access\"\n"); fprintf(stderr, " bytes per access \033[1mto\033[2m stdout\n"); fprintf(stderr, " or - writes as many bytes as are available \033\[1mfrom\033[2m\n"); fprintf(stderr, " stdin \033[1mto\033[2m physical memory starting at \"address\"\n"); fprintf(stderr, " using \"access\" bytes per access.\n"); fprintf(stderr, " Note that both \"address\" and either \"size\" or the\n"); fprintf(stderr, " number of available bytes from stdin must be a multiple of\n"); fprintf(stderr, " \"access\", and \"access\" must either be %d, %d, %d or %d.\033[0m\n", sizeof(uint8_t), sizeof(uint16_t), sizeof(uint32_t), sizeof(uint64_t)); exit(-1); } template<typename T> void readOrWrite(uint8_t *src, uint8_t *mem) { if(src) *(T *) mem = *(T *) src; else { T t = *(T *) mem; assert(write(1, &t, sizeof(T)) == sizeof(T)); } } int main( int argc, char *argv[]) { int fd, pageSize = getpagesize(), size = 0, n; uint8_t *mem, *b = 0, *buffer = 0; // Paranoia check to ensure that page size is a power of 2. assert((pageSize != 0) && !(pageSize & (pageSize - 1))); if (argc == 3) do { #define CHUNK_SIZE 1000 assert(b = buffer = (uint8_t *) realloc(buffer, size + CHUNK_SIZE)); assert((n = read(0, buffer + size, CHUNK_SIZE)) >= 0); size += n; } while(n); else if(argc == 4) size = strtoul(argv[3], 0, 0); else usage(argv[0]); off_t address = strtoul(argv[1], 0, 0); size_t access = strtoul(argv[2], 0, 0); if(address % access || size % access) usage(argv[0]); assert((fd = open ("/dev/mem", O_RDWR)) >= 0); size_t s = (((address & (pageSize - 1)) + size - 1) / pageSize + 1) * pageSize; mem = (uint8_t *) mmap(NULL, s, PROT_READ | PROT_WRITE, MAP_SHARED, fd, address & ~(pageSize - 1)); assert(mem != MAP_FAILED); for(uint8_t *i = mem; i < mem + size; i += access) { #define ROW(t) sizeof(t): readOrWrite<t>(b, i); break switch(access) { case ROW(uint8_t); case ROW(uint16_t); case ROW(uint32_t); case ROW(uint64_t); default: usage(argv[0]); } if(b) b += access; } free(buffer); munmap(mem, getpagesize()); close(fd); return 0; }

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Building multi-file modules
by Arlie Stephens May 8, 2013

May 8, 2013

Hi Folks, I've got a module, call it foo, presently built from a single source file, drivers/char/foo.c It's gotten enormous, so I want to split it. Ideally I'd keep the original name for one of the source files. So what I want is a module named foo, build from source files foo.c, bar.c and baz.c kbuild is being uncooperative. The following works: obj-$(CONFIG_FOO) += foo_renamed.o foo_renamed-objs := foo.o bar.o baz.o I'd just prefer not to rename either the module or the original source file. Is this supposed to be possible, and if so, how? I'm on RHEL 6.1, aka kernel 2.6.32, in case that matters. Also, in case that matters, I'm building the module into the kerenl ("y" not "m" in the config.) ----what I've tried---- The following gives me warnings from make: obj-$(CONFIG_FOO) += foo.o foo-objs := foo.o bar.o baz.o The following never compiles foo.c: obj-$(CONFIG_FOO) += foo.o foo-objs := bar.o baz.o Thanks for any insight, -- Arlie (Arlie Stephens arlie(a)worldash.org)

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read PCI memory and config spyce through /dev/mem
by Warlich, Christof May 7, 2013

May 7, 2013

Hi, I'd like to look at some of my PCI devices through /dev/mem. My kernel config has "Filter access to /dev/mem" (STRICT_DEVMEM) switched off, so as root, I should have unrestricted access. I get my PCI device's BAR address through /proc/iomem, e.g.: $ cat /proc/iomem ... f7600000-f7603fff : r8169 ... Ok, so there should be 16K of PCI memory from my ethernet card starting at f7600000, which is 4150263808 in decimal to be used With dd. But: $ dd if=/dev/mem bs=1 count=1024 skip=4150263808 dd: reading `/dev/mem': Bad address 0+0 records in 0+0 records out 0 bytes (0 B) copied, 6.6658e-05 s, 0.0 kB/s The kernel config help says that _PCI_ memory access is even possible with STRICT_DEVMEM enabled. Can anyone give me a hint what I may do wrong? Thanks a lot, Chris

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Re: Device mapper api v/s block device driver api
by Rami Rosen May 7, 2013

May 7, 2013

Hi Just of pure curiosity, can you please provide a link to the blog you had mentioned? Regards Rami Rosen http://ramirose.wix.com/ramirosen On May 6, 2013 10:46 PM, "neha naik" <nehanaik27(a)gmail.com> wrote: > Hi, > Reading a blog on device mapper api got me confused about when one > should use device mapper api and when to use block device driver api. > I was under the impression that even for stackable device drivers (say a > customized block device driver on top of lvm or such) we need to use the > block device driver api. But, > reading about the device mapper api i have started thinking that it may > not be the case. > May be for stackable device drivers device mapper is the solution. > What do you think? What are the pros and cons of device mapper v/s block > device driver > > Regards, > Neha > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies(a)kernelnewbies.org > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > >

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Major number for multipath block devices
by Kumar amit mehta May 7, 2013

May 7, 2013

Hi, I've a query regarding the major numbers for block devices that the block layer would provide (upon invocation of register_blkdev() with '0' as the major number) for the multipath devices, i.e. If I have one logical volume(Talking in LVM terms)and have two paths to the same logical volume, then it seems that the two logical volumes will have the same major number(refer [1]). I think, to achieve this, dm-mapper would consult with dm-multipath, but I'm finding it difficult to locate this piece of interaction (considering that my assumption is true) between the device mapper layer and the dynamic multipath kernel module. Can someone please educate me here. [1] http://plone.uconn.edu/Members/jar02014/linux-lvm-and-multipath-configration. -Amit

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Device mapper api v/s block device driver api
by neha naik May 6, 2013

May 6, 2013

Hi, Reading a blog on device mapper api got me confused about when one should use device mapper api and when to use block device driver api. I was under the impression that even for stackable device drivers (say a customized block device driver on top of lvm or such) we need to use the block device driver api. But, reading about the device mapper api i have started thinking that it may not be the case. May be for stackable device drivers device mapper is the solution. What do you think? What are the pros and cons of device mapper v/s block device driver Regards, Neha

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