07-10-2014
Quote:
Originally Posted by
Corona688
I can see why it would cause issues when contiguous pages aren't available, but why using contiguous pages cause pages to become discontinuous?
Oracle doesn't technically request "contiguous" pages, it requests large pages. To get those large pages, the OS must coalesce smaller pages.
Oracle uses the large page, releases it, then something else requests normal size pages and the large page gets fragmented. Oracle comes back and requests larges pages...
Rinse, lather, repeat.
The coalescing necessary to create the large pages can have some nasty performance impacts as it tends to lock up virtual memory management while it's happening. And for any OS instance, VM management tends to get very single threaded when memory gets tight. Processes won't start or hang because fork() and brk() calls block while the virtual memory manager thrashes about.
This can be really bad with Oracle on Solaris using ZFS because the ZFS ARC cache uses lots of small pages and isn't exactly quick in letting them go, and the standard recommendation is "let the ARC cache get as big as it wants, it doesn't hurt anything." Umm, wrong.
This User Gave Thanks to achenle For This Post:
10 More Discussions You Might Find Interesting
1. Filesystems, Disks and Memory
Hello:
Environment is: Oracle 817 on IBM RS/6000 AIX 433
I have 4GB RAM on the box and Page/Swap is about the same.
Presently I am using close to 1GB of RAM towards 5 instances of ORACLE production environments.
How can I know, how much of memory/RAM is used for :
Oracle Processes , I... (2 Replies)
Discussion started by: ST2000
2 Replies
2. UNIX for Dummies Questions & Answers
Hi,
Please let me know more details on fragmentation in redhat linux and command to check fragmented files?
Thanks,
Bache Gowda (2 Replies)
Discussion started by: bache_gowda
2 Replies
3. Shell Programming and Scripting
HI All,
I need a script to reboot a linux box from a windows box.
The script needs to run automatically whenever a sitescope alerts with an error message.
Have searched for this in the forums, but could not get something relative.
Pls. let me know the various alternatives we have to do... (2 Replies)
Discussion started by: Crazy_murli
2 Replies
4. HP-UX
hi,
if I do top, I get
Memory: 19277012K (5868296K) real, 33860312K (11294208K) virtual, 795392K free
If I do swapinfo -tm I get:
% swapinfo -tm
Mb Mb Mb PCT
TYPE AVAIL USED FREE USED
dev 16384 0 16383 0%
dev ... (3 Replies)
Discussion started by: JamesByars
3 Replies
5. Linux
Hi
I'be recently installed Virtouzzo on Centos 5 on 16GB box , but the system could only see 4 GB of RAM, I installed the package kernel-PAE, but the virtuozzo kernel still can't see the full memory.
even the kernel system can see 16GB of RAM
is there any idea bout that ?
Thanks (2 Replies)
Discussion started by: Raied
2 Replies
6. Solaris
I have certain questions.
1) How can i see the memory of the unix box.
2) How can i see the size of the database on the box
3)can anyone suggest an article or tutorial that explains the concept of
file systems and mount point in UNIX.
4)How can i see the dblink on the server
I... (5 Replies)
Discussion started by: asalman.qazi
5 Replies
7. Solaris
my system has 128G of installed memory. top, vmstat shows the system has just over 10G of free memory on the system. but as per prstat o/p the usage is just 50-55G is there anyway i can find which process/zone is using more memory ?
System has 3 zones and all running application servers.
... (1 Reply)
Discussion started by: fugitive
1 Replies
8. UNIX for Dummies Questions & Answers
Hi,
I've been able to mount my linux box to a windows machine, but I can't seem to mount my linux box to another linux box I have. (I know I could scp, but for other reasons I need to do it this way) Samba is installed.
Here is an example where I mount to a Win machine.--> works fine
mount... (12 Replies)
Discussion started by: jdilts
12 Replies
9. Red Hat
Hi
I have a linux box and need to access from windows graphically
# uname -a
Linux pc-l416116 2.6.18-155.el5 #1 SMP Fri Jun 19 17:06:47 EDT 2009 i686 i686 i386 GNU/Linux
What components do I need to install on Linux and windows to do that?
TIA (6 Replies)
Discussion started by: magnus29
6 Replies
10. How to Post in the The UNIX and Linux Forums
Hello my dear friends,
Two file are auto generated from mon - fri at different directories on same windows box.Every day i have to copy the file, rename it (specific name)and ftp it to linux box specified directory.
is it possible to automate this process,If yes this has to be done from windows... (1 Reply)
Discussion started by: umesh yadav
1 Replies
LEARN ABOUT DEBIAN
munlock
MLOCK(2) BSD System Calls Manual MLOCK(2)
NAME
mlock, munlock -- lock (unlock) physical pages in memory
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sys/mman.h>
int
mlock(const void *addr, size_t len);
int
munlock(const void *addr, size_t len);
DESCRIPTION
The mlock() system call locks into memory the physical pages associated with the virtual address range starting at addr for len bytes. The
munlock() system call unlocks pages previously locked by one or more mlock() calls. For both, the addr argument should be aligned to a mul-
tiple of the page size. If the len argument is not a multiple of the page size, it will be rounded up to be so. The entire range must be
allocated.
After an mlock() system call, the indicated pages will cause neither a non-resident page nor address-translation fault until they are
unlocked. They may still cause protection-violation faults or TLB-miss faults on architectures with software-managed TLBs. The physical
pages remain in memory until all locked mappings for the pages are removed. Multiple processes may have the same physical pages locked via
their own virtual address mappings. A single process may likewise have pages multiply-locked via different virtual mappings of the same
pages or via nested mlock() calls on the same address range. Unlocking is performed explicitly by munlock() or implicitly by a call to
munmap() which deallocates the unmapped address range. Locked mappings are not inherited by the child process after a fork(2).
Since physical memory is a potentially scarce resource, processes are limited in how much they can lock down. A single process can mlock()
the minimum of a system-wide ``wired pages'' limit and the per-process RLIMIT_MEMLOCK resource limit.
These calls are only available to the super-user.
RETURN VALUES
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the
error.
If the call succeeds, all pages in the range become locked (unlocked); otherwise the locked status of all pages in the range remains
unchanged.
ERRORS
The mlock() system call will fail if:
[EPERM] The caller is not the super-user.
[EINVAL] The address given is not page aligned or the length is negative.
[EAGAIN] Locking the indicated range would exceed either the system or per-process limit for locked memory.
[ENOMEM] Some portion of the indicated address range is not allocated. There was an error faulting/mapping a page.
The munlock() system call will fail if:
[EPERM] The caller is not the super-user.
[EINVAL] The address given is not page aligned or the length is negative.
[ENOMEM] Some portion of the indicated address range is not allocated.
SEE ALSO
fork(2), mincore(2), minherit(2), mlockall(2), mmap(2), munlockall(2), munmap(2), setrlimit(2), getpagesize(3)
HISTORY
The mlock() and munlock() system calls first appeared in 4.4BSD.
BUGS
Allocating too much wired memory can lead to a memory-allocation deadlock which requires a reboot to recover from.
The per-process resource limit is a limit on the amount of virtual memory locked, while the system-wide limit is for the number of locked
physical pages. Hence a process with two distinct locked mappings of the same physical page counts as 2 pages against the per-process limit
and as only a single page in the system limit.
The per-process resource limit is not currently supported.
BSD
August 10, 2004 BSD