slab usage in linux
Hi List, I have a few queries regarding slab memory and it's usage. I have seen slab cache increase by even 1GB, over two to three days on a stable system.(The system was sending and receiving bulk amounts of packets). When is slab usually freed? Also when I analyzed /proc/slabinfo, I was able to see that the number of active slab objects were increasing mostly for task_struct, dentry_cache and proc_inode_caches. When are these caches allotted objects, in general? Can anyone please explain the behavior related to slab allocation; or point to any reference material? Thanks, Sowmya. =-=-= Notice: The information contained in this e-mail message and/or attachments to it may contain confidential or privileged information. If you are not the intended recipient, any dissemination, use, review, distribution, printing or copying of the information contained in this e-mail message and/or attachments to it are strictly prohibited. If you have received this communication in error, please notify us by reply e-mail or telephone and immediately and permanently delete the message and any attachments. Thank you ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
floating points in kernel space
hi all, i read somewhere that there is no floating point arithmatic supported in the kernel space . is it true?? but the floating point registers and even floating point arithmatic units are all handled by the.( kernel i think). thanks in advance for help... -- *MOHIT VERMA* ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: floating points in kernel space
On Tue, Jan 4, 2011 at 6:43 AM, mohit verma mohit89m...@gmail.com wrote: hi all, i read somewhere that there is no floating point arithmatic supported in the kernel space . is it true?? but the floating point registers and even floating point arithmatic units are all handled by the.( kernel i think). thanks in advance for help... HI it is true , the floating point is not supported on printk , AFAIK the only way to handle is to send it like HEX values and then some other application like perl or python transform it to floating point Hope it helps Regards Victor Rodriguez -- MOHIT VERMA ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: floating points in kernel space
Hi Mohit, On Tue, Jan 4, 2011 at 4:43 AM, mohit verma mohit89m...@gmail.com wrote: hi all, i read somewhere that there is no floating point arithmatic supported in the kernel space . is it true?? but the floating point registers and even floating point arithmatic units are all handled by the.( kernel i think). That is correct. In some architectures, attempts to use floating point from the kernel will work. I've seen some x86 code that uses it. However, with ARM for example, there is no float support in the kernel, and some ARM architectures have no floating point support in the hardware either. For ARM, there is a kernel implemented emulation of the floating point instructions, but these can only be called from user space. There are also some ARM software floating point libraries (aka soft-fp) which can be used from user space (which are much more efficient than using the kernel emulation library) The kernel also doesn't support 64-bit division using the C divide statement, unless you happen to be running on a 64-bit architecture. There are some helper functions to achieve 64-bit division (see div64.h). Dave Hylands ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: slab usage in linux
Hi I cc: the reply to the new list address. I hope you don't mind Now, let's what I can share here On Tue, Jan 4, 2011 at 18:49, Sowmya Sridharan sowmya.sridha...@tcs.com wrote: I have seen slab cache increase by even 1GB, over two to three days on a stable system.(The system was sending and receiving bulk amounts of packets). No kidding? 1 Gig? Wow But that's alright, I think that still make sense ... highly frequent sock related cache creation I guess slabtop -s c would tell you the highest cache size ... When is slab usually freed? AFAIK when it can no longer grow same like page cache, it will grow to fill your RAM until it exhausts everything left by anonymous page allocation plus some amount of reserved pages. And AFAIK too, it's tunable, but I couldn't recall which kernel parameters that control it. Also when I analyzed /proc/slabinfo, I was able to see that the number of active slab objects were increasing mostly for task_struct, dentry_cache and proc_inode_caches. When are these caches allotted objects, in general? task_struct-- during new process creation dentry_cache -- after reading directory entry metadata from a block devices and cache them proc_inode_cache -- almost similar like above, but this one is strictly for /proc entries. -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: floating points in kernel space
Hi.. On Tue, Jan 4, 2011 at 22:44, Dave Hylands dhyla...@gmail.com wrote: That is correct. In some architectures, attempts to use floating point from the kernel will work. I've seen some x86 code that uses it. AFAIK, once x86 didn't supported due to floating point related registers are not correctly (or even doing?) saved and restored during context switching. So maybe it is fixed now... -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: ASLR implementation
Hi... On Tue, Jan 4, 2011 at 20:04, Zubin Mithra zubin.mit...@gmail.com wrote: Hi, I recently read about the Linux kernel implementing ASLR to prevent buffer overflow attacks. nope...that is done to make symbol address guessing harder I would like to have a look at how this is implemented by reading the kernel source code. Could someone offer a few pointers on where to start looking?(It would make my work slightly easier.) try http://lxr.linux.no/#linux+v2.6.36/arch/x86/vdso/vma.c -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: fixed memory bytes
Please reply all..I added back list. On Tue, Jan 4, 2011 at 1:58 PM, mohit verma mohit89m...@gmail.com wrote: thnx john,. but i know that this indicates to compiler to align the structure to its nearest boundries. is that so? I am not sure of your definition of boundary, but I would say it does the opposite. It tells the compiler not to align the struct to boundaries. -- John ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: floating points in kernel space
On Tue, Jan 4, 2011 at 22:44, Dave Hylands dhyla...@gmail.com wrote: That is correct. In some architectures, attempts to use floating point from the kernel will work. I've seen some x86 code that uses it. AFAIK, once x86 didn't supported due to floating point related registers are not correctly (or even doing?) saved and restored during context switching. So maybe it is fixed now... -- I've often wondered about this oft-cited kernel behaviour too, in my naivety. I understand that this must be on a per-arch basis, but does this mean that the kernel doesn't police FP access at _all_ (perhaps this is what Mohit means too)? Does code like X for example have to access it directly, or does it just use the GPU? What about other user-space code - does it have a separate library and do its own security? Video drivers? Sorry if these are basic questions, I grepped for float in the kernel but as-yet the associated code looks really arcane to me - if anyone could answer any of these questions generally (if that's possible) that would be very helpful with visualizing the mechanism. Maybe I'm looking in the wrong place. When I started looking at the kernel I imagined this small, neat, concise piece of highly efficient code so I wasn't surprised there was no float (don't laugh - how one learns :-/ ) ... I suppose any float per-arch 'hacks' (to get a larger word size) would not be worth the overhead of the mode switch and extra code? Thanks Julie ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: fixed memory bytes
i have seen many places in kernel where the variables specially the structures should be of fixed size independent of the architecture. i went through the definitions of them but dint get clearly (or frankly say ...dint get them even a bit) . Hi Mohit I'm not sure whether we are interpreting your question correctly. Do you mean 1. you've seen some code in the kernel which you think means the size of a structure/ variable (and its resulting binary footprint) is set to be the same (in bytes), regardless of the architecture, and you are confused about it? 2. you think that there should be a way of fixing the structure/variable (binary footprint) size to be the same (in bytes) regardless of the architecture and you are wondering if this is possible? In my (uninformed) opinion (2) is not be possible with the kernel due to portability issues - not only do natural word types differ (as others here are explaining) but you have no control over what optimization settings the kernel's user might set in gcc, for example. This is one of the problems with trying to maintain closed-source drivers and other binary code for the kernel, as I understand. Thanks Julie ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Adding Module to kernel
Dear All, I have a kernel module which i want to add to kernel permanently(I was doing it dynamically) . How can we achieve this ? Regards, Praveen ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: fixed memory bytes
A nice kernel document regarding unaligned memory access. It may not be directly answering all the questions asked, but once gone through and understood completely, it will become easy to figure out how to write portable kernel code. http://lxr.linux.no/#linux+v2.6.36/Documentation/unaligned-memory-access.txt Rajat On Wed, Jan 5, 2011 at 4:29 AM, julie Sullivan kernelmail@gmail.com wrote: i have seen many places in kernel where the variables specially the structures should be of fixed size independent of the architecture. i went through the definitions of them but dint get clearly (or frankly say ...dint get them even a bit) . Hi Mohit I'm not sure whether we are interpreting your question correctly. Do you mean 1. you've seen some code in the kernel which you think means the size of a structure/ variable (and its resulting binary footprint) is set to be the same (in bytes), regardless of the architecture, and you are confused about it? 2. you think that there should be a way of fixing the structure/variable (binary footprint) size to be the same (in bytes) regardless of the architecture and you are wondering if this is possible? In my (uninformed) opinion (2) is not be possible with the kernel due to portability issues - not only do natural word types differ (as others here are explaining) but you have no control over what optimization settings the kernel's user might set in gcc, for example. This is one of the problems with trying to maintain closed-source drivers and other binary code for the kernel, as I understand. Thanks Julie ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Kernel compilation
I'm new to the list and would like to say hello to everyone. Now on to the meat. I have tried to compile a kernel with a grsec patch 5 times now using a couple of different methods and I keep getting a No init found and Couldn't support optional features errors every time at bootup. I'm trying to use a vanilla 2.6.32.27 kernel on 10.04 Ubuntu and it compiles fine, just will not boot. I've tried CONCURRENCY_LEVEL=`getconf _NPROCESSORS_ONLN` fakeroot make-kpkg --initrd --append-to-version=-custom kernel_image kernel_headers, CONCURRENCY_LEVEL=3 make-kpkg --initrd --append-to-version=-586 kernel_image kernel_headers modules_image. I have all the reqs for building kernels such as build-essentials, fakeroot, kernel-package, kernel-wedge, nurces-dev and qt for xconfig. These are the steps I've taken. DL the kernel image from kernels.org, get the patch from grsec.net, untar the kernel, cd into the directory created, do a 'cp /boot/config-`uname -r` .config', 'make oldconfig', apply the patch, then either 'make menuconfig' or 'make xconfig'. Then I do a 'make-kpkg clean' and run one of the commands in the first paragraph above. I get the debs built and can install them just fine, but I keep getting the same errors. I've cut out as many Experimental options I thought might cause a problem and still get a kernel panic at boot. Anyone have a clue what I'm doing wrong? Scott ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel compilation
Hi Scott :) On Wed, Jan 5, 2011 at 12:34, scott redhowlingwol...@nc.rr.com wrote: I'm new to the list and would like to say hello to everyone. Now on to the meat. I have tried to compile a kernel with a grsec patch 5 times now using a couple of different methods and I keep getting a No init found and Couldn't support optional features errors every time at bootup. I'm trying to use a vanilla 2.6.32.27 kernel on 10.04 Ubuntu and it compiles fine, just will not boot. My first question is: did the patching go successfully? were you applying the correct grsec version against a matching vanilla kernel version? And last, maybe you can attach your kernel .config content...and one of fine people here will try to decipher what's wrong with it :) -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
how opensolaris stores the major number ?
Hi, zfs_mknode is the function use by mknod syscall to create device special file in solaris kernel. I traverse the code and just found how they stores the minor number which is in znode's(disk inode of Linux) attributes struct called sa_bulk_attr field uint16_t sa_buftype which is of 16bit only. so, it just store minor number in this field. And I am failed to understand where/how the solaris exact stores major number from code traversing. so, can somebody clarify where/how the major number stores in solaris code or in znode(disk inode). the source is available online and following link is of zfs_znode.c file having zfs_mknode function... http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/fs/zfs/zfs_znode.c Regards, Deepen Mehta ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel compilation
On 01/05/2011 01:46 AM, Mulyadi Santosa wrote: Hi Scott :) On Wed, Jan 5, 2011 at 12:34, scottredhowlingwol...@nc.rr.com wrote: I'm new to the list and would like to say hello to everyone. Now on to the meat. I have tried to compile a kernel with a grsec patch 5 times now using a couple of different methods and I keep getting a No init found and Couldn't support optional features errors every time at bootup. I'm trying to use a vanilla 2.6.32.27 kernel on 10.04 Ubuntu and it compiles fine, just will not boot. My first question is: did the patching go successfully? were you applying the correct grsec version against a matching vanilla kernel version? And last, maybe you can attach your kernel .config content...and one of fine people here will try to decipher what's wrong with it :) The patch was matched and was successful. It compiled with no errors. Just the 'no init' at boot. I'll post my .config later today as it's late here and have to work. I'm beginning to think it may have something to do with the limits on file size as I got a few warnings about out-of-range sizes. I have it set to 1024. Thanks for your reply, Scott Thanks for your reply. ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Kernel compilation
On Wed, 5 Jan 2011, scott wrote: I'm new to the list and would like to say hello to everyone. Now on to the meat. I have tried to compile a kernel with a grsec patch 5 times now using a couple of different methods and I keep getting a No init found and Couldn't support optional features errors every time at bootup. I'm trying to use a vanilla 2.6.32.27 kernel on 10.04 Ubuntu and it compiles fine, just will not boot. I've tried CONCURRENCY_LEVEL=`getconf _NPROCESSORS_ONLN` fakeroot make-kpkg --initrd --append-to-version=-custom kernel_image kernel_headers, CONCURRENCY_LEVEL=3 make-kpkg --initrd --append-to-version=-586 kernel_image kernel_headers modules_image. I have all the reqs for building kernels such as build-essentials, fakeroot, kernel-package, kernel-wedge, nurces-dev and qt for xconfig. These are the steps I've taken. DL the kernel image from kernels.org, get the patch from grsec.net, untar the kernel, cd into the directory created, do a 'cp /boot/config-`uname -r` .config', 'make oldconfig', apply the patch, then either 'make menuconfig' or 'make xconfig'. Then I do a 'make-kpkg clean' and run one of the commands in the first paragraph above. I get the debs built and can install them just fine, but I keep getting the same errors. I've cut out as many Experimental options I thought might cause a problem and still get a kernel panic at boot. Anyone have a clue what I'm doing wrong? you are clearly using ubuntu, so here's a simpler recipe i've used successfully. 1) configure and build your kernel from the source 2) sudo make modules_install 3) sudo make install 4) sudo update-initramfs -c -k kernel version goes here 5) sudo update-grub the drawback to the above is that your kernel is not built as an official *package* but for testing purposes, it should do. you'll get your kernel installed under /boot, your modules installed, a new initramfs image, and your grub file updated. can you try it this way and see if it makes a difference? rday -- Robert P. J. Day Waterloo, Ontario, CANADA http://crashcourse.ca Twitter: http://twitter.com/rpjday LinkedIn: http://ca.linkedin.com/in/rpjday ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
