3
votes
1answer
56 views

Artificially prime buffer cache?

Is it beneficial to artificially prime the buffer cache when dealing with larger files? Here's a scenario: A large file needs to be processed, line by line. Conceptually, it is easy to parallelize ...
0
votes
0answers
16 views

how to find where buffers/cache are and how to clean them up? [duplicate]

I want to create 20gb ram disk for ANSYS to work in yet on free -g I see: And personally I have not created any ram drives yet. So I wonder how to maximize avaliable ram: how to locate what is using ...
2
votes
0answers
43 views

Reduce cache size of flash storage devices

For various benefits Linux uses a memory cache for writes to removable stogare devices like memory sticks. This cache seems to be quite large on my system, which leads to some annoying behavior. For ...
1
vote
1answer
60 views

Random application crashes in Linux

Sometimes after booting my computer, some applications fail to start: they crash. They're usually the largest ones, such as firefox, thunderbird or virtualbox. Rebooting or cleaning the cache usually ...
0
votes
1answer
49 views

should I reduce /dev/shm size?

I have a server wity 8 GB RAM Mem: Total 8031464 Used 5146344 Free 2885120 If I execute # df it always returns this tmpfs 4015732 0 4015732 0% /dev/shm What does it ...
1
vote
1answer
102 views

Clear Memory Cache on Amazon EC2

In our project we have a few tests which run for about 3-4 hours continuously. In due course, the tests fail as they couldn't find enough memory. On googling, I found that running the following ...
5
votes
1answer
140 views

How to use an SSD for caching, so my hard disks can spin down?

I've got a file server with a bunch of disks running together in a BTRFS pool and want to add an SSD for caching. I'm not mainly after speeding up things, but want to catch the regular small accesses ...
3
votes
1answer
333 views

SSD as a read cache for FREQUENTLY read data

I'm looking for ways to make use of an SSD to speed up my system. In “Linux equivalent to ReadyBoost?” (and the research that triggered for me) I've learned about bcache, dm-cache and EnhanceIO. All ...
3
votes
0answers
470 views

Tune write disk cache flushing algorithm

I would like to use the free memory for write cache. Linux does that automatically, but it has some weird flushing algorithm that I would like tuned for my use. I have recently used ddrescue to copy ...
13
votes
1answer
6k views

How do you empty the buffers and cache on a Linux system?

Prior to doing some benchmarking work how would one free up the memory (RAM) that the Linux Kernel is consuming for its buffers and cache?
4
votes
2answers
398 views

Are there any ways or tools to dump the memory cache and buffer?

As the title, I want to check out what files are loaded in buffer. Just so it's clear, the buffers & cache I'm referring to are what show up when you run the free -m command: $ free -m ...
1
vote
1answer
2k views

Is “sync” before drop_caches necessary?

I have read a lot of docs saying, it is good idea to do a sync before doing echo [1,2,3] > /proc/sys/vm/drop_caches. I am not able to understand why it is needed, since drop_cache is a ...
4
votes
1answer
552 views

How can I tune Ubuntu for running from a flash drive?

I feel like this is a bit of a duplicate of this other question about making caching more aggressive, but I tried a lot of the suggestions there and I just can't figure out why I'm having trouble. My ...
1
vote
1answer
77 views

How to stop CACHE instance from Shell Script

I want to restart CACHE(database that I am using) Instance from shell script. What I did is created a function in the shell script named resatrt_cache. restart_cache() { ccontrol stop instancename ...
6
votes
1answer
658 views

How to configure Linux to cache file metadata in preference to contents?

I’d like to set the system up to use most RAM for file system metadata caching, but only a reasonably small amount for read/write caching and prefetching files. Ideally I would like to be able to ...
3
votes
1answer
471 views

How to guarantee writes are physically committed before reported completed?

When my system boots, as it probes the external, USB-attached hard drive, I get the message Assuming drive cache: write through in the dmesg output, tagged with the device name of the external drive. ...
2
votes
1answer
132 views

Keeping disk caches when hibernating

Is there a way to keep disk caches when hibernating Linux? I understand and agree that dropping them is the best option all-around. But my system is unresponsive after resume and I would like to give ...
8
votes
1answer
280 views

Linux cache evictions

Looking at how the VFS cache on my Linux machine behaves, I can see that even when effectively idle (crond and most other daemons stopped, interfaces down) the amount of free memory gradually ...
1
vote
2answers
234 views

TLB cache flusing when a page is swapped out

I recently heard that Linux simply flushes the TLB cache when the corresponding data in that physical address is swapped out, resulting in underutilization of the TLB. I don't know whether all OSes do ...
0
votes
1answer
337 views

Does linux have something like supercache?

I installed http://www.superspeed.com/desktop/supercache.php for windows and the result is awesome. Every program I run is faster. Basically it uses the memory to cache data. Simple idea. I also use ...
4
votes
1answer
274 views

Limit disk buffer usage in SLES 11SP2 to allow more efficient memory overcommit on esxi host

When running VMs on an ESXi host, you can overcommit the memory. Example: host == 20GB physical RAM The amount of RAM allocated to each VM is VM1 == 10gb VM2 == 10gb VM3 == 10gb VM4 == 10gb The ...
13
votes
2answers
782 views

Why does Linux purge the memory cache when it is nearly full?

Here's what the memory graph looks like on a VPS running CentOS with 512MB of RAM and nginx/php-fpm/mysqld serving (mostly static) content to a couple thousand visitors per day. (those are days on ...
3
votes
2answers
317 views

linux disk caching affects access times reported by stat?

On Ubuntu 12.04 I did the following stat a file cat the same file stat the file again cat the file again after 5 min stat the file The access time reported at 3. reflects the point at which 2. was ...
3
votes
2answers
137 views

RAID Lag-Behind Burst Write

I would like to setup RAID1 so that a ramdisk in the RAID configuration has occasional synchronisation with a physical disk (that is very battery intensive to run, so I hope to let it spinout). Is ...
1
vote
2answers
2k views

How to bypass youtube's local cache?

Youtube performance here in Brazil has been terrible lately. Checking my browser's activity I can see that my ISP has a local Youtube cache and serves videos in 1.7 MB chunks. Talking to some friends ...
2
votes
1answer
231 views

How to utilize extended attributes for image preview?

Is there any file browsers for Linux that cache image previews, just like Windows Explorer cache them to a file named Thumbs.db? As in the latest ext3/4 filesystems, an inode can hold extended ...
2
votes
1answer
428 views

Running a query without the OS cache

I want to emulate a client site who doesn't have much caching because they have so much I/O all the time. I want to run a SQL query on my machine (on my VM to be precise) with the same limitations ...
4
votes
1answer
590 views

Drop a specific file from the Linux filesystem cache?

I know I can drop everything from the Linux filesystem cache, but is there a way to drop just one specific file? Or prevent a file from being cached? Or tell a process not to cache any files it ...
2
votes
2answers
534 views

mbcache documentation

I want to experiment with mbcache kernel module, but I'm having trouble finding the documentation for it. If I understood correctly, mbcache allows the use of a fast SSD disk to act as a transparent ...
3
votes
1answer
2k views

What is the buffers column in the output from free?

These questions briefly list the format of the free command, noting that buffers is kernel memory that must be written out to disk and cache is file data that does not need to be written disk. On my ...
1
vote
2answers
409 views

Embedded device: How to do raw reads and write to flash (emmc/movinand) bypassing file system cache

I have an embedded device with a flash memory running linux. I want to do raw read writes on the flash part but I also want to avoid any file system cache. How can I do this? Any pointers?
2
votes
3answers
499 views

Is there a way to tell the system to keep a folder to reside in memory?

I'm developing a Java EE web application and I'm trying to speed up the testing process. To do so I was wondering if there is a way to tell the system to keep my build folder in system memory?
6
votes
1answer
15k views

How to read the local DNS cache contents?

I know that on Windows I can issue ipconfig /displaydns and I see the local DNS's cache content. How can I list the DNS's cache content in Linux? I would like to get as much as cross-distro solution ...
5
votes
2answers
5k views

Cleancache vs zram?

I have an old laptop here with only 512 MB of RAM. Since a few kernel releases, I am using zram to convert 256 MB of it to a compressed ramdisk which is then used as swap. This has proved to be very ...
1
vote
0answers
946 views

What is meant by cache aliasing? [closed]

What is the meant by cache aliasing? I searched around some, but wasn't satisfied with the answers I found. I also saw two associated terms, instruction cache aliasing & data cache aliasing. ...
2
votes
0answers
587 views

Linux kernel slab usage growing on embedded system

I'm in the process of QA/debugging a project on a custom embedded linux system. The problem we're VERY tight on memory, and even a couple megs can cause issues with our software. What I'm seeing ...
4
votes
1answer
2k views

What options are there for tuning Linux file system caching?

What various types of caching are possible in the ext3 file system and how can their values be changed using system calls or other methods? I don't want to use commands or tools.
17
votes
7answers
5k views

Linux equivalent to ReadyBoost?

Is there a kernel module or some other patch or something similar to Windows' ReadyBoost? Basically I'm looking for something that allows disk reads to be cached on a Flash drive.
25
votes
3answers
2k views

Does grep use a cache to speed up the searches?

I have noticed that subsequent runs of grep on the same query (and also a different query, but on the same file) are much faster than the first run (the effect is easily noticeable when searching ...
7
votes
5answers
13k views

DNS queries not using nscd for caching

I'm trying to use nscd (Nameservices Cache Daemon) to cache DNS locally so I can stop using Bind to do it. I've gotten it started and ntpd seems to attempt to use it. But everything else for hosts ...