I want to know whether this is possile or ever been tried out.
I want to obtain a chuck of memory using mmap()
I do it so :
And hold on to that memory, when a process requests for memory, some memory is assigned from this chunk.
In Linux is it possible to control where the new process gets it's memory from? Can i create a process that will only get memory from the chunk of memory i reserved?
Hello. I'm writing some random access i/o software on Solaris 8 using mmap64 to memory map large files (my test file is ~25 GB).
The abbreviated code fragment is:
fd = open(cbuf,O_RDONLY|O_LARGEFILE);
struct stat statbuf;
fstat(fd,&statbuf);
off_t len =... (0 Replies)
We recently have been seeing the following type of error on our development server. Being somewhat new to HP-UX I was hoping to get some insight. Here is what I have found.
I have been doing some research.
/usr/lib/dld.sl: Call to mmap() failed - TEXT /u07/mdev/lib/libCLEND.sl... (2 Replies)
I'm using select() to monitor multiple file descriptors (inet sockets) in application. But this application must also collaborate with other applications on the same host via shared memory (mmap'ed file) due to performance reasons. How can I become notification that mmaped memory is changed or... (1 Reply)
Dear Experts,
i have a problem related to mmap(), when i run my program on sun for 64 bit which is throwing SIGBUS when it encounters mmap() function, what is the reason how to resolve this one, because it is working for 32 bit.
with regards,
vidya. (2 Replies)
Descriptions:
Develop a program that uses mmap() to map a file to memory space. Prepare such a file by yourself and do the follows.
<LI class=MsoNormal>Display the content of the file after mapping; <LI class=MsoNormal>Output how many digits included in the file; <LI class=MsoNormal>Replace... (1 Reply)
Hi
I want to lock or prevent a portion of memory which I allocated. So I tried MLOCK, MPROTECT and some like this. But all these functions works only on page border. Can I know why that so.
Is that possible to protect a portion of memory which is in middle of the page.
Example.
int A;
... (1 Reply)
I'm new to kernels and C, and I am tinkering around trying to understand OpenBSD's secure memory management. I'm stumped on a couple points.
I've read up on malloc() which was apparently modified years ago to allocate memory using mmap. First question, that would be this here, right?
... (4 Replies)
Discussion started by: dcicc
4 Replies
LEARN ABOUT DEBIAN
bup-margin
bup-margin(1) General Commands Manual bup-margin(1)NAME
bup-margin - figure out your deduplication safety margin
SYNOPSIS
bup margin [options...]
DESCRIPTION
bup margin iterates through all objects in your bup repository, calculating the largest number of prefix bits shared between any two
entries. This number, n, identifies the longest subset of SHA-1 you could use and still encounter a collision between your object ids.
For example, one system that was tested had a collection of 11 million objects (70 GB), and bup margin returned 45. That means a 46-bit
hash would be sufficient to avoid all collisions among that set of objects; each object in that repository could be uniquely identified by
its first 46 bits.
The number of bits needed seems to increase by about 1 or 2 for every doubling of the number of objects. Since SHA-1 hashes have 160 bits,
that leaves 115 bits of margin. Of course, because SHA-1 hashes are essentially random, it's theoretically possible to use many more bits
with far fewer objects.
If you're paranoid about the possibility of SHA-1 collisions, you can monitor your repository by running bup margin occasionally to see if
you're getting dangerously close to 160 bits.
OPTIONS --predict
Guess the offset into each index file where a particular object will appear, and report the maximum deviation of the correct answer
from the guess. This is potentially useful for tuning an interpolation search algorithm.
--ignore-midx
don't use .midx files, use only .idx files. This is only really useful when used with --predict.
EXAMPLE
$ bup margin
Reading indexes: 100.00% (1612581/1612581), done.
40
40 matching prefix bits
1.94 bits per doubling
120 bits (61.86 doublings) remaining
4.19338e+18 times larger is possible
Everyone on earth could have 625878182 data sets
like yours, all in one repository, and we would
expect 1 object collision.
$ bup margin --predict
PackIdxList: using 1 index.
Reading indexes: 100.00% (1612581/1612581), done.
915 of 1612581 (0.057%)
SEE ALSO bup-midx(1), bup-save(1)BUP
Part of the bup(1) suite.
AUTHORS
Avery Pennarun <apenwarr@gmail.com>.
Bup unknown-bup-margin(1)