It is an extension of memory address space which is logically appended to the physical memory of a computer by the Memory Management Unit (MMU) of its processor. It is normally realized in operating systems by utilizing free disk space to implement such memory extension and may also be referred to ...

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55
votes
3answers
49k views

Meaning of the buffers/cache line in the output of free

Why does my server show total used free shared buffers cached Mem: 12286456 11715372 571084 0 81912 6545228 -/+ buffers/cache: 5088232 7198224 ...
37
votes
3answers
22k views

In Linux, what is the difference between “buffers” and “cache” reported by the free command?

This is an old question that I've seen from time to time. My understanding of it is rather limited (having read about the differences a long time ago, but the factoid(s) involved never really stuck). ...
25
votes
17answers
23k views

Caching/preloading files on Linux into RAM

I have a rather old server that has 4GB of RAM and it is pretty much serving the same files all day, but it is doing so from the hard drive while 3GBs of RAM are "free". Anyone who has ever tried ...
24
votes
5answers
18k views

swap partition vs file for performance?

What is better for performance? A partition closer to the inside of the disk will have slower access times, and we must wait for the drive to switch between the OS and swap partitions. On the other ...
11
votes
2answers
13k views

What is “a lot” of Page Faults?

I am monitoring the memory object in Windows 2k8, and am tracking the Page Faults/sec counter. Is there any threshold to determining what is an excessive amount of page faults? Or should I be more ...
10
votes
1answer
4k views

Difference Between Private Memory Limit and Virtual Memory Limit in IIS

I want to set the max limit on the physical memory an application can use in IIS 7. Should I set a limit on Private Memory Limit or Virtual Memory Limit? Can some one point me to documentation of all ...
9
votes
1answer
361 views

Ballooning occuring on SQL server

From what I understand ballooning should occur only when the host begins to run out of physical memory, somewhere above 90% usage. I have an SQL server running in a three node cluster (64 GB RAM in ...
7
votes
4answers
5k views

Understanding virtual memory usage > swap + physical on Linux

I have a process that is reporting in 'top' that it has 6GB of resident memory and 70GB of virtual memory allocated. The strange thing is that this particular server only has 8GB physical and 35GB of ...
7
votes
4answers
489 views

What are the exact conditions based on which Linux swaps process(s) memory from RAM to a swap file?

My server has 8Gigs of RAM and 8Gigs configured for swap file. I have memory intensive apps running. These apps have peak loads during which we find swap usage increase. Approximately 1 GIG of swap is ...
6
votes
2answers
1k views

Memory overcommitment on VMware ESXi 5.0

I would like to understand better the possibilities of VmWare ESXi memory overcommitment. I've read this paper from VmWare, so I am familiar with general concepts, such as hypervisor swapping, memory ...
6
votes
3answers
20k views

How do I tell what process is causing kswapd to be in use?

I see kswapd using 100% CPU... how can I tell on which process's behalf kswapd is being used so much?
5
votes
4answers
6k views

Constantly Increasing swap size in Linux and Swap space not being reclaimed?

I have a 8GB RAM linux box on which 4 tomcat servers are running. One of the them is set to 3000MB memory(jvm -Xms and -Xmx setting) and others are set to 1500MB. The swap partition is also set to ...
5
votes
2answers
324 views

Automatically suspend/hibernate a process when too much memory taken

I'm running a small Debian compute cluster on 8-core PCs with 16GB of RAM. I'm running batches of about 1k tasks (each batch has a total expected time of a month to be finished). A single task is ...
4
votes
1answer
10k views

How to limit the memory used by an application in IIS?

The IIS worker processes are taking lot of memory on our servers. I want to limit the memory each application can use. I am confused whether I should set a limit on Virtual Memory Limit, or Private ...
4
votes
1answer
498 views

How do you measure the memory footprint of a set of forked processes?

Say I've got a process using 200MB of memory, and it fork()s: python -c "import os; data='x'*200000000; os.fork(); raw_input()" Programs like 'top' will show each process using 200MB, with very ...
4
votes
3answers
3k views

Windows Server task manager displays much higher memory use than sum of all processes' working set size

I have a 16 GB Windows Server 2008 x64 machine mostly running SQL Server 2008. The free memory as seen in Task Manager is very low (128 MB at the moment), i.e. about 15.7 GB are used. So far, so good. ...
3
votes
2answers
686 views

Linux OOM disk I/O. Also: swap, what is it good for?

I'm having problems with the OOM killer on one of my Linux (2.6.37) installs. The computer has 4GB of memory which I sometimes utilize fully. In those cases, I expect the OOM handler to come in and ...
3
votes
3answers
87 views

Virtual Server Memory not a power/multiple of 2

In the old times (before virtualization), memory came in powers/multiples of 2, because that is the way memory is manufactured. Nowadays that we create virtual servers that don't have real physical ...
3
votes
3answers
408 views

High Memory 64bit server, not using all ram

I have several high memory linux servers running centos 64bit, and after 10-20 days of uptime I have noticed on all of these servers they dont actually use all the ram available to then (they all have ...
3
votes
1answer
624 views

What is shrink_slab, and why is it showing up in /var/log/messages?

I'm investigating some application issues on a Linux system and noticed this around the time of the most recent problem, but not close enough to be definitively related: Jun 7 17:51:49 localhost ...
3
votes
2answers
4k views

How to sort top result on virtual memory on Redhat Linux?

There is an interactive key "M" to sort by memory, which seems to be sorting on resident memory. Is there a way to sort on virtual memory? I happen to be working on Redhat Linux, but the question is ...
3
votes
1answer
688 views

Reducing Virtual memory Page File Size on Windows 7

I've upgraded my PC to 16GB RAM and I've noticed the page file is at 16GB as well. Since I decided to go SSD, hard drive space is a bit limited so I would like to try and claim some of that 16GB back. ...
3
votes
1answer
548 views

Performance affects of compressing Program Files on Windows / NTFS

What are the performance affects of compressing Program Files on Windows NTFS? On a fast, multicore machine, the overhead of decompression is minimal. Machines are generally disk bound, and if you ...
3
votes
2answers
206 views

How can I keep important VMs in memory without disabling swap?

VM Host -> Xenon E5-2440 w/ 48G mem... Everything runs CentOS6.5 (2.6.32-431) I have 4 guest VMs running each w/ 2G of memory. Their disk images are local files. The host machine is also running a ...
3
votes
0answers
44 views

How can I measure disk cache churn on Linux? [duplicate]

Possible Duplicate: Is there a way to get Cache Hit/Miss ratios for block devices in Linux? I have a file server which serves out large (25GB-1TB+) files over the network from local ...
2
votes
2answers
96 views

Linux virtual memory tuning to workaround disk I/O issue

I am having a problem with a Linux server that it is writing to much to disk, thus I am having a slow response time due to a big IO wait. I already check smart values for the disks and are OK. This is ...
2
votes
1answer
1k views

Is it bad if your Virtual Bytes count is high in an application pool in IIS?

Related to What does Virtual Bytes mean in Worker Processes pane in IIS7.5 Manager? I have a server running a few different sites. We're seeing some performance and memory issues. When I go to ...
2
votes
2answers
717 views

DefaultAppPool Settings in IIS

With a 4Gb RAM server and Windows 2003, I've determined by trial and error that setting a virtual RAM limit of 1.6 seems to kill the runaway processes without causing the normal processes to restart ...
2
votes
1answer
2k views

How to tune system settings for mongoDB on Linux?

Trying to squeeze a lot out of one question here -- please bear with me. Although the MongoDB man pages make several useful recommendations about system settings like ulimit ...
2
votes
1answer
288 views

Windows Server: Prevent process swapping/paging

Is there a possibility to prevent swapping for a single process? This process is an in-memory-database and should not be moved to virtual ram. all other processes should still be swap-able. I ...
2
votes
1answer
288 views

Do IIS App Pools using Network Service account share memory?

We're trying to tune our IIS farm, and I'm trying to get my head around how Windows allocates resources in our current setup. We have a pretty standard layout. We host 30+ ASP/ASP.NET sites on our ...
2
votes
1answer
3k views

Definition of these metrics recorded in /proc/vmstat on RHEL 5.3 (paging/swapping?)

This question relates to the definition of specific metrics recorded in /proc/vmstat on RHEL 5.3. I'm using nmon to monitor a load test which consists of simulating 2500 users carrying out a days ...
2
votes
1answer
60 views

What is System Code Total Bytes

I am trying to use perfmon, and according to MSDN, the "System Code Total Bytes" counter ... Shows the size, in bytes, of pageable operating system code currently in virtual memory. It is a ...
2
votes
1answer
100 views

How to interpret increasing SHR reported by top?

The man page for top defines SHR as: t: SHR -- Shared Mem size (kb) The amount of shared memory used by a task. It simply reflects memory that could be potentially shared with other ...
2
votes
0answers
144 views

virtual memory commited

After a server bounce happens, and after around 40-45 days time period, we receive continuous “Committed Virtual Memory” alerts which indicates the usage of swap space in the magnitude of >4GB This ...
2
votes
2answers
426 views

Cannot change pagefile size on Windows 2008

I have a windows 2008 (virtual) machine, which I want to add a pagefile to. However, any time I try to set the page file size, after a reboot it jumps back down to 0. Why is this?
1
vote
4answers
2k views

How do I tell if a Linux system has hugemem?

i386 Linux kernels can be configured for a 2, 3 or 4 GiB limit on virtual address space per process, AFAIK. Is there something I can query in /proc or elsewhere to tell how the currently-running ...
1
vote
2answers
826 views

Linux out of memory on VPS

On my VPS (CentOS) 4GB ram (2 + 2 dynamically assigned when needed) and i have tomcat running with following options JAVA_OPTS="-Xms256m -Xmx2048m -XX:MaxPermSize=256m". Now when i try to start ...
1
vote
1answer
349 views

100GB Virtual Memory on 64GB server without swap [duplicate]

Possible Duplicate: Understanding virtual memory usage > swap + physical on Linux We have the following process: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND ...
1
vote
2answers
783 views

Where's the Swap File/Partition?

I'm investigating the virtual memory configuration of a Debian based Amazon EC2 instance, and as my background isn't in system admin, I'm slightly confused by what I'm seeing. We're using MongoDB, ...
1
vote
1answer
2k views

Mysql using high VIRT memory and RES is compartively

is there a way to reduce the VIRT mem usage? I am not sure what the reason is for such high usage. It has reached upto 12g as well. Using top command Tasks: 348 total, 1 running, 344 sleeping, 0 ...
1
vote
1answer
828 views

Virtual Memory Limit in IIS 7

The Virtual Memory Limit(KB) setting in IIS 7 on our production server has a value 0. Does it means our application is not using any virtual memory or does it means, there is no maximum limit on the ...
1
vote
1answer
779 views

Why do I get swap space related errors when I still have lots of free memory in Solaris 10?

I am seeing a few of my services suffering/crashing with errors along the lines of "Error allocating memory" or "Can't create new process" etc. I'm slightly confused by this since logs show that at ...
1
vote
1answer
1k views

Large virtual memory size of ElasticSearch JVM

I am running a JVM to support ElasticSearch. I am still working on sizing and tuning, so I left the JVM's max heap size at ElasticSearch's default of 1GB. After putting data in the database, I find ...
1
vote
1answer
55 views

Virtual memory and CPU usage catch 20/20?

I am looking at this system below with ensuring we have enough memory to carry out day to day tasks, we have been hitting a bottleneck recently because there was only a 2GB page file, I've changed ...
1
vote
1answer
158 views

SQL Server Page File On 3TB San Drive

We have a Windows Server 2008 R2 box with 288GB of RAM. The system has created a page file about about the same size. This is expected, however, when I try to move the file to a SAN drive that is ...
1
vote
2answers
3k views

How do I find the root cause of Memory pressure failure on an SQL server 2008?

One of the servers I have been performance monitoring started throwing the following warnings from the Resource-Exhaustion-Detector: Windows successfully diagnosed a low virtual memory condition. ...
1
vote
1answer
940 views

How to find out who used all RAM (UPDATED)?

Sometimes I find that 100% of my small Debian machine's RAM is used, but I can't figure out how to find this leak: top show that all memory is used, but I can't find any process that consumed this ...
1
vote
1answer
2k views

How much space is in a Solaris /tmp filesystem?

On Solaris, the /tmp filesystem is a filesystem of type "tmpfs". It's implemented in the kernel by allocated space from the virtual memory pool. That means allocation interacts with the available RAM ...
1
vote
1answer
1k views

How to use AWE for Windows Server 2003 (32-bit) and SQL Server 2005 (32-bit)?

The server is Windows Server 2003 SP2 (32-bit), running SQL Server 2005 SP3 (32-bit). I believe the server has 4 GB of physical RAM. The machine has crashed twice in the last week and it is a ...