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Centos Malloc Error

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and DevelopmentX Window System Print Subscribe to Linux Subscribe to Newsletters When Linux Runs Out of Memory by Mulyadi Santosa 11/30/2006 Perhaps you rarely face it, but once you do, you surely know what's wrong: lack of free memory, or Out of Memory (OOM). The results are typical: you can linux malloc no longer allocate more memory and the kernel kills a task (usually the current linux kernel malloc running one). Heavy swapping usually accompanies this situation, so both screen and disk activity reflect this. At the bottom of linux malloc implementation this problem lie other questions: how much memory do you want to allocate? How much does the operating system (OS) allocate for you? The basic reason of OOM is simple: you've asked for more unix malloc than the available virtual memory space. I say "virtual" because RAM isn't the only place counted as free memory; any swap areas apply. Exploring OOM To begin exploring OOM, first type and run this code snippet that allocates huge blocks of memory: #include #include #define MEGABYTE 1024*1024 int main(int argc, char *argv[]) { void *myblock = NULL; int count = 0; while (1) { myblock

Linux Malloc Source Code

= (void *) malloc(MEGABYTE); if (!myblock) break; printf("Currently allocating %d MB\n", ++count); } exit(0); } Compile the program, run it, and wait for a moment. Sooner or later it will go OOM. Now compile the next program, which allocates huge blocks and fills them with 1: #include #include #define MEGABYTE 1024*1024 int main(int argc, char *argv[]) { void *myblock = NULL; int count = 0; while(1) { myblock = (void *) malloc(MEGABYTE); if (!myblock) break; memset(myblock,1, MEGABYTE); printf("Currently allocating %d MB\n",++count); } exit(0); } Notice the difference? Likely, program A allocates more memory blocks than program B does. It's also obvious that you will see the word "Killed" not too long after executing program B. Both programs end for the same reason: there is no more space available. More specifically, program A ends gracefully because of a failed malloc(). Program B ends because of the Linux kernel's so-called OOM killer. The first fact to observe is the amount of allocated blocks. Assume that you have 256MB of RAM and 888MB of swap (my current Linux settings). Program B ended at: Currently allocating 1081 MB On the other hand, program A ended at: Currently allocating 3056 MB Where did A

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Linux Malloc Alignment

or posting ads with us Stack Overflow Questions Jobs Documentation Tags Users Badges Ask Question linux malloc limit x Dismiss Join the Stack Overflow Community Stack Overflow is a community of 4.7 million programmers, just like you, helping each other. Join them; linux malloc system call it only takes a minute: Sign up Causing malloc() to return NULL on CentOS up vote 4 down vote favorite 1 I'm about to teach an introductory computer science course in C and I'd like to demonstrate to students why http://www.linuxdevcenter.com/pub/a/linux/2006/11/30/linux-out-of-memory.html they should check whether malloc() returned a NULL. My plan was to use ulimit to restrict the amount of available memory such that I could exercise different code paths with different limits. Our prescribed environment is CentOS 6.5. My first attempts to make this happened failed and the shell showed "Killed". This led to me discovering the Linux OOM killer. I have since tried to figure out the magic set of incantations that will cause the results I'm looking for. http://stackoverflow.com/questions/20725217/causing-malloc-to-return-null-on-centos Apparently I need to mess with: /etc/sysctl.conf ulimit -m ulimit -v vm.overcommit_memory (which apparently should be set to 2, according to an Oracle article) This far either I get "Killed" or a segmentation fault, neither of which is the expected outcome. The fact that I'm getting "Killed" with vm_overcommit_memory=2 means that I definitely don't understand what's going on. If anyone can find a way to artificially and reliably create a constrained execution environment on CentOS so that students learn how to handle OOM (and other?) kinds of errors, many course instructors will thank you. c centos malloc ulimit share|improve this question asked Dec 22 '13 at 1:15 Jason Foster 4111 3 void *mymalloc(size_t n) { return rand() % 3 ? malloc(n) : NULL; } then #define malloc mymalloc –user529758 Dec 22 '13 at 1:18 1 Have you tried a hard limit in /etc/security/limits.conf? –Elliott Frisch Dec 22 '13 at 1:25 I really like the "random failure" approach, but I can see some students saying "Sure, you can simulate a failure but what happens in reality?" I'm planning to do some demos on an Arduino (where malloc() had better fail), but would like to be able to demo in a Linux shell. –Jason Foster Dec 22 '13 at 1:35 1 @JasonFoster (Just FYI, in reality, malloc() will hardly ever fail on Linux. Almost all modern OSes overcommit memory, meaning that they make mallo

here for a quick overview of the site Help Center Detailed answers to any questions you might http://unix.stackexchange.com/questions/94479/jemalloc-and-other-errors-making-redis-on-centos-6-4 have Meta Discuss the workings and policies of this site About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads https://patchwork.kernel.org/patch/7986951/ with us Unix & Linux Questions Tags Users Badges Unanswered Ask Question _ Unix & Linux Stack Exchange is a question and answer site for users of Linux, linux malloc FreeBSD and other Un*x-like operating systems. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top jemalloc and other errors making redis on centos 6.4 up vote 17 down vote favorite 2 I am setting centos malloc error up a new, dedicated, centos 6.4 system with redis. I have installed redis many times, but have never hit this issue (and have never been on centos 6.4 before). cd redis-2.6.16 sudo make install error: sh: ./mkreleasehdr.sh: Permission denied and later: zmalloc.h:50:31: error: jemalloc/jemalloc.h: No such file or directory zmalloc.h:55:2: error: #error "Newer version of jemalloc required" When I try to build jemalloc directly (from the /src area of the redis tarball), other errors include: cd src && make jemalloc sh: ./mkreleasehdr.sh: Permission denied make[1]: Entering directory `/tmp/rediswork/redis-2.6.16/src' make[1]: *** No rule to make target `jemalloc'. Stop. make[1]: Leaving directory `/tmp/rediswork/redis-2.6.16/src' make: *** [jemalloc] Error 2 I also tried redis 2.6.7 and have the same issue. I have dug all over and can find no path forward. centos make share|improve this question edited Oct 13 '13 at 22:32 asked Sep 30 '13 at 4:25 samsmith 256129 migrated from serverfault.com Oct 10 '13 at 17:38 This question came from our site for system and network administrators. blog.gbinghan.com/2

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