Questions tagged [memory]

Synonym for: RAM - Acronym for: Random Access Memory, a type of computer data storage.

A random-access device allows stored data to be accessed in very nearly the same amount of time for any storage location, so data can be accessed quickly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations. Therefore the time to access a given data location varies significantly depending on its physical location.

Today, random-access memory takes the form of integrated circuits. Strictly speaking, modern types of DRAM are not random access, as data is read in bursts, although the name DRAM/RAM has stuck. However, many types of SRAM, ROM, OTP, and NOR flash are still random access even in a strict sense. RAM is often associated with volatile types of memory (such as DRAM memory modules), where its stored information is lost if the power is removed.

Wikipedia article (source) also contains more information on RAM.

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Any benefit or detriment from removing a pagefile on an 8 GB RAM machine?

I'm running Windows 7 on a dual core, x64 AMD with 8 GB RAM. Do I even need a page file? Will removing it help or hurt performance? Would it make a difference if this is a server or a desktop? Does Windows 7 vs. Windows 2008 make a difference with a…
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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 Swap: 24571408 54528 24516880 I have no idea on…
Muahmmad Zeeshan
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What does Virtual memory size in top mean?

I am running top to monitor my server performance and 2 of my java processes show virtual memory of up to 800MB-1GB. Is that a bad thing? What does virtual memory mean? And oh btw, I have swap of 1GB and it shows 0% used. So I am confused. Java…
kapso
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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 running a ram-drive can witness that It's awesome in…
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Why drop caches in Linux?

In our servers we have a habit of dropping caches at midnight. sync; echo 3 > /proc/sys/vm/drop_caches When I run the code it seems to free up lots of RAM, but do I really need to do that. Isn't free RAM a waste?
ivcode
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Dump a linux process's memory to file

Is it possible to dump the current memory allocated for a process (by PID) to a file? Or read it somehow?
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How does vm.overcommit_memory work?

When I use the default settings: vm.overcommit_memory = 0 vm.overcommit_ratio = 50 I can read these values from /proc/meminfo file: CommitLimit: 2609604 kB Committed_AS: 1579976 kB But when I change vm.overcommit_memory from 0 to 2, I'm…
Mikhail Morfikov
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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). As I understand it, Buffers Are used by…
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Linux: how to explicitly unswap everything possible?

I've launched something that took lots of memory and now everything lags a lot. I guess all applications' memory has gone to swap in order to free some space for the memory-intensive process, and now everything is slowly returning to RAM when…
kolypto
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How to read memory usage in htop?

Here is my htop output: For example, I'm confused by this ruby script: How much physical memory is it using? 3+1+8+51+51? 51? 51+51?
Lai Yu-Hsuan
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Does memtest86+ test memory which is used to run itself?

One of the common server failure scenarios is bad DRAM, sometimes even when ECC memory is used. memtest86+ is one of the most useful tools to diagnose DRAM problems. As it loads itself at the start of the memory, I've been wondering if memtest86+…
Robin
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How to understand the memory usage and load average in linux server

I am using a linux server which has 128GB of memory and 24 cores. I use top to see how much it is used. Its output is pasted at the end of the post. Here are two questions: (1) I see that each of the running processes occupies a very small…
Tim
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vSphere education - What are the downsides of configuring VMs with *too* much RAM?

VMware memory management seems to be a tricky balancing act. With cluster RAM, Resource Pools, VMware's management techniques (TPS, ballooning, host swapping), in-guest RAM utilization, swapping, reservations, shares and limits, there are a lot of…
ewwhite
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DIMMs: Single vs. Double vs. Quad Rank

What difference does the 'Rank' of DIMMs make to server memory? For example, when looking at server configurations I see the following being offered for the same server: 2GB (1x2GB) Single Rank PC3-10600 CL9 ECC DDR3-1333 VLP RDIMM 2GB (1x2GB) Dual…
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How to find memory usage of individual Windows services?

Task Manager shows the overall memory usage of svchost.exe. Is there a way to view the memory usage of individual services? Note this is similar to Finegrained performance reporting on svchost.exe
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