The shared-memory tag has no usage guidance.
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36 views
Across systems, How a process communicate with other process?
I have learnt below IPC mechanisms,
BSD style half-duplex pipes
SYSV style message queues
SYSV style semaphore sets
SYSV style shared memory segments
BSD style sockets
Half-duplex pipe can be used ...
1
vote
1answer
75 views
How to know shared memory between two processes?
I need to know the amount of memory shared between two processes, that is, the intersection of their shared memories.
Any ideas?
Thanks!
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0answers
17 views
The same program which uses 'mmap' behaves differently on the different machines
I am running an application which uses a huge memory mapped file on two different machines (CentOS 7).
I found that the same program's performance is significantly different when it's running on two ...
1
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1answer
104 views
How can i calculate the size of shared memory available to the system
According to the rhel document, the total amount of shared memory available on the system equals to shmall*PAGE_SIZE.
After I completed the installation of RHEL6, the value of the shmall kernel ...
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0answers
19 views
Chat program not sending the data to other user
I am writing two programs in Ubuntu which will run and each terminals and chatting can be done . But when I type something in terminal 1 , text doesn't goto terminal 2 and when I type in terminal 2 ,...
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0answers
70 views
Discrepancy between shared memory from /proc/meminfo and ipcs
Running free -hm outputs:
total used free shared buffers cached
Mem: 15G 15G 389M 321M 169M 11G
-/+ buffers/cache: ...
0
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0answers
45 views
How do you install Oracle on Linux when you get the error “ORA-27101: shared memory realm does not exist”?
I am installing Oracle 11 on CentOS 7.2. I have installed it before on servers with less RAM.
I get this error:
ORA-01034: ORACLE not available ORA-27101: shared memory realm does
not exist
...
1
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1answer
186 views
Limit memory usage of a user
I have a computing cluster of 44 cores and 256GB memory running Ubuntu and I'd like to limit the number of CPUs and memory used by certain users. Limiting memory usage would be more important. So for ...
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1answer
445 views
Kernel parameter SHMALL and SHMAX [closed]
I am using Red Hat Enterprise Linux Server release 5.11 (Tikanga) as OS and rdbms is 11gR2 software. I have created a database with memory_target=3 GB and
physical RAM=7 GB. My DB service is getting ...
0
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1answer
124 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 ...
2
votes
1answer
126 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
242 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
...
1
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1answer
137 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
209 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
1k 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
279 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
35 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
votes
1answer
506 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
82 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
6k 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
votes
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
1k 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 ...
2
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2answers
3k 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 ...
5
votes
1answer
4k 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
5k 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
171 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'...
0
votes
2answers
188 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
votes
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
362 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
votes
5answers
4k 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
votes
2answers
1k 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
981 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
3k 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
votes
1answer
611 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?
