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13 views

i whant to clean the shared and the buff/cache memory [duplicate]

I want to clean the shared and the buff/cache memory, I'm not expert in linux but I want to learn. I have 2 gb of ram when i go through firefox the memory used is 900-1000 mb is this normal?? ...
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1answer
37 views

Unix Domain Socket with VM

Is it a true statement that, shared memory does not work between a host OS and guest OS, but a Unix Domain Socket (specifically udp) can communicate between the two? An in depth explanation would be ...
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0answers
30 views

Why does .text region of shared libraries is not flagged as VM_SHARED?

When I'm using shmem/mmap to share memory between processes I can see with pmap that it creates virtual memory area that marked as shared. Example: Address Kbytes RSS Dirty Mode ...
2
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1answer
47 views

non-reentrant libraries in shared memory?

I found this Q&A saying shared libraries can be shared between processes using shared memory. It seems like it would be impossible, though, to share code between processes without some pretty ...
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0answers
99 views

Extremely high shmem usage

I'm trying to debug the issue that's periodically taking down my work machine. It's an OOM-type problem, and based on this /proc/meminfo output: Total: 32902608 kB MemFree: 4054100 kB ...
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1answer
69 views

determine the actual memory usage of several processes that share a large memory segment

I just took a look at the output of top and it showed me (amongst other processes) the following: As once can see I have ten processes consuming approx 10GB each so 100GB in total. The computer ...
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0answers
155 views

Opcache and shared memory issue

I installed zend_opcache on my server box , but I can not increase opcache.memory_consumption over 1600 . (example : 2048) . after increase following error occur in server : Fatal Error Fatal Error ...
3
votes
1answer
498 views

Memory layout of dynamic loaded/linked library

when loading a shared library in Linux system, what is the memory layout of the shared library? For instance, the original memory layout is the following: +-----------+ |heap(ori) | +-----------+ |...
2
votes
1answer
259 views

Why does the clock need a shared memory segment?

This is a combination of programming and Linux question but I think it suits better here. I am writing an application that works with ipcs (shared memory segments) and after each running I am ...
0
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1answer
32 views

attaching to Unix shared segment

Can a UNIX program running as root attach to a shared memory segment created by another user with permissions allowing access only to creator?
6
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1answer
435 views

File backed, locked shared memory and disk interaction

Varnish, a HTTP accelerator, uses a ~80MB file backed SHM log that is mlock()ed into memory. The Varnish docs recommend to store the file on tmpfs to avoid unnecessary disk access. However if the ...
3
votes
1answer
74 views

Grsecurity subject mode x

I am conducting some research on Grsecurity on Hardened Gentoo, see http://en.wikibooks.org/wiki/Grsecurity. To be more specific, I am trying to find an example where subject mode x makes a difference....
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3answers
4k views

On system memory… specifically the difference between `tmpfs,` `shm,` and `hugepages…`

I've been curious lately about the various Linux kernel memory based filesystems. Note: As far as I'm concerned, the questions below should be considered more or less optional when compared with a ...
4
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1answer
3k views

can not create /dev/shm

I need to create /dev/shm on an embedded ARM system. From "Installed The Latest Changes to Current and......". I see that it can be created with mkdir /lib/udev/devices/shm, but I'm wondering what ...
4
votes
1answer
869 views

Resize / remount /dev/shm not working

I've got a linux box dedicated to playing host to an Oracle server installation. It's got 4Gb RAM and by default, 50% (2Gb) has been allocated to /dev/shm. I want to change this to 3Gb, but I am ...
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2answers
2k views

Hugepages in linux - how to make sure that java process will start using hugepages

I'm running java server on Red Hat Enterprise Linux Server release 5.9. Recently I started to use HugePages as it has some advantages I would like to use. System was configured correctly (as many ...
4
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1answer
3k views

operation in /dev/shm causes overflow

I am repeating tens of thousands of similar operations in /dev/shm, each with a directory created, files written, and then removed. My assumption used to be that I was actually creating directories ...
6
votes
1answer
4k views

use `/run/shm` (formerly `/dev/shm`) as a temp directory

Is it good practice to create a directory in /run/shm (formerly /dev/shm) and use that like a temp directory for an application? Background: I am writing black box tests for a program which does a ...
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0answers
161 views

Viewing shared segments created by shmget

I'm trying to "visualize" shared memory between two processes. I've created a little server-client example where the client writes some data to a shared memory location and the server reads from it. I'...
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2answers
164 views

Why is there no critical section in the pipe?

Why is there no critical section in the pipe? For example, as in shared memory. In pipe have general data, which in common use in joint processes, but in the shared memory also have general data, ...
6
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1answer
2k views

What is “SYSV00000000”?

In my dmesg this appeared when my window manager (xfwm4, part of XFCE) crashed: xfwm4[3936]: segfault at 7f3c7c523770 ip 00007f3c7c523770 sp 00007ffffea1ee28 error 15 in SYSV00000000 (deleted)[...
0
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2answers
349 views

Linux - get shared memory values from Perl script

I'm trying to get shared memory information from a linux box. I'm looking for shmmax, shmmni, shmall, msgmax, msgmni, semmsl, semmns etc. How to get all those values from a Perl script. any help is ...
5
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5answers
3k views

Share memory between a virtual machine and the host

Through shmget and shmat, I am able to access the data stored in one program from another program. Here's the gist of the code: key=ftok("shared.c",'c'); shmid=shmget(key,1024,0644|IPC_CREAT); data=...
3
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2answers
885 views

IPC: Shared memory killed process notification

In shared memory system, when two processes share a shared memory segment, after one process is killed, how will the other running process be notified of the killed process by the shared memory system ...
5
votes
1answer
957 views

Linux - why is kernel.shmall so low by default?

I run DB2 on Linux where I have to allocate the vast majority of memory on the machine to shared memory segments. This page is typical of the info that I've found about shmall/shmmax: http://www....
6
votes
1answer
2k views

What are shmpages in laymans terms?

What exactly are shmpages in the grand scheme of kernel and memory terminology. If I'm hitting a shmpages limit, what does that mean? I'm also curious if this applies to more than linux
11
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1answer
589 views

What are the differences in shared memory between early and modern Unix systems?

How could processes share memory in early versions of Unix? How does this compare with modern implementations of shared memory?