0
votes
1answer
24 views

Can high disk cache usage lead to external fragmentation and ultimately to page allocation failures?

We're getting page allocation failures on a Linux server (3.2 kernel). We've been told the problem is directly related to the high use of the memory for cache; this would lead to external ...
0
votes
1answer
68 views

MongoDB: big size of mapped memory

I'm not expert in mongo memory management but some things confuse me. I use Mongo 2.4.9 and I have a replica sets for three nodes. I have performed db.serverStatus().mem and see that size of mapped is ...
3
votes
3answers
256 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 ...
1
vote
0answers
36 views

Stack , data and address space limits on an Ubuntu server

I am running an Ubuntu server which has around 5000 users. The users are allowed to SSH in to the system. So in order to cap the memory used up by a process I have capped the address space limits ...
4
votes
2answers
247 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 ...
1
vote
2answers
75 views

Impact on various Linux commands on a Varnish server

I know Varnish use memory mapped technique for caching data in memory, what if I execute the following commands on a machine, are there any penalty on the overall Varnish's performance? e.g. Total ...
2
votes
1answer
972 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 ...
1
vote
1answer
154 views

Using Linux /proc/meminfo to avoid overloading server via swapping

I am trying to find a metric to use that will tell me if starting another process estimated to use N bytes of memory will have an adverse impact on system performance. I know that the /proc/meminfo ...
2
votes
1answer
78 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 ...
1
vote
2answers
580 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
297 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
0answers
84 views

Getting the virtual memory address for (major) page faults

On a Linux (Cent OS 5) system, I have a process that accesses a large amount of memory mapped files. The process is generating a large amount of page faults because the aggregated size of the mapped ...
0
votes
4answers
223 views

Fast small static file serving on a VPS - avoiding the Disk

I need to serve a large number of very small static files (e.g. 1Million, ~1KB), from a VPS. My current favoured approach is Nginx, but my main concern is hitting slow VPS disks. Is there an ...
3
votes
1answer
368 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 ...
3
votes
0answers
43 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 ...
3
votes
1answer
543 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
3k 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 ...
7
votes
4answers
4k 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 ...
5
votes
3answers
15k 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?
3
votes
2answers
619 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 ...
0
votes
2answers
420 views

New 64 bit linux system has regular processes (ps, grep etc) taking up way too much VIRT mem

We just moved from a 32-bit machine to a 64-bit machine. We have quickly ran out of memory despite the new boxes have twice as much ram as the old boxes. Running a simple ps command will illustrate ...
7
votes
4answers
435 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 ...
48
votes
3answers
42k 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 ...
21
votes
18answers
21k 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 ...
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 ...
21
votes
5answers
15k 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 ...
35
votes
3answers
19k 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). ...