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Questions tagged [iowait]

Iowait is the time a CPU is in an idle state, waiting for IO-operations to complete.

In UNIX/Linux systems, is the amount of time or percentage of time, in which the CPU is idle and waits for completion of IO-operations. This state of the CPU can be seen in the output of the top-command under wa.

To test the behavior of this value (to produce iowait-time),e.g. the dd-command can be used:

dd if=/dev/sda of=/dev/null

Note that if there is an other process that is using the same CPU as this command, it is possible that the other process is using this CPU and the CPU won't be in idle state nor in iowait-state.

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High iowait with java processes on linux

I have a concurrent system with many machines/nodes involved. Each machine run several JVMs doing different stuff. It is a "layered" architecture where each layer consists of many JVM running across the machines. Basically the top-layer JVM receives…
Per Steffensen
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How to automatically compile LESS into CSS on the server?

Friend designer of mine was compiling his LESS file manually and uploading it with Coda (Remote Site) spending lots of precious time. He asked me: Is it possible to automatically detect file change on the Linux server and compile without delay at…
romaninsh
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Cassandra Amazon EC2, Read Performance experiments

I need some help improving Cassandra read performance. I am concerned about degradation of read performance as the size of the column family increases. We have the following stats on single-node Cassandra. Operating System: Linux - CentOS release…
Asim
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Debugging 100% iowait problem in linux

I've been trying to trace down why I have 100% iowait on my box. If I do something like a mysql select query, system goes to 100% iowait (on more than one cpu on my server,) which kills my watchdogs and sometimes kills httpd itself. In vmstat I see…
gilm
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Cassandra Amazon EC2 , lots of IOWait

We have the following stats on single node cassandra on Amazon EC2/Rightscale m1.large instance with 2 ephemeral disks with raid0. (7.6 GB Total Memory) 4 GB RAM is allocated to cassandra Heap, 800MB is Heap NEW size. following stats are from…
Asim
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ANR with high iowait in android

I am running youtube application and getting an ANR and device is responsive slow. And I am getting iowait 64% E ActivityManager: 98% TOTAL: 12% user + 20% kernel + 64% iowait + 0% irq + 1.1% softirq So how we can identify causing application for…
Saurabh Pareek
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How to get the system ioWait

How can i get the systems ioWait? This would be preferable by using info the /proc interface( i guess its written somewhere in there) so an app could detect this, but an external call to exec() from my app would be acceptable.
Quamis
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High iowait on sdcard - process stuck for 5-15 seconds

I have IOT devices (arm64) running Ubuntu with SD cards (formatted as ext4 with Journaling) where my application logging(python logging library) is done to files on that SD card, overall the write speed (as reported by iotop) is around 40KB/s (the…
Uriel Katz
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Getting iowait with top and awk

For a benchmark script, I need to extract the iowait % right after a little operation. For now, the best way I find was this: IOWAIT=top -bn2 | awk '$1~/Cpu/ {print $6}' | sed -n '2p' | tr -d '%wa,' The correct output is something like 2.1: First,…
Brice
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Dedicated database server heavy iowait spikes

We have a dedicated database server that runs PostgreSQL 8.3 on linux debian. The database is being regularly queried for a lot of data while updates/inserts happen frequently also. Periodically the database does not respond for a small duration (…
John Papastergiou
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Perfino java process IOwait consuming "APPARENT DEADLOCK!!!"

we reboot process java perfino every night, after reboot it starts consuming 24-30% IOWait and the software doesn't work until 30-40 minutes... The output when it is starting is: 2022-09-05 09:09:53,390 INFO [main]…
Juanjo
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Can CPU execute other processes if the iowait is 99% now

If there is only one cpu and the IOwait is 99%, is the cpu still able to execute other processes, if so, is only 1% cpu resource could be used? or the other process could also use 100% cpu resource although under the scene of 99% Iowait. I read the…
Jack
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Graphite Server High IO Wait Time

Our Graphite server is facing CPU and disk bottlenecks. The main problem is that the %IO Wait time is always in the range of 40%. We run it on a 2-core CPU on a RHEL server with 7.5 GiB RAM. (Agreed, our CPU configuration is primitive, but we'd like…
sgrover
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Get IO Wait time as % in python

I am writing a python script to get some basic system stats. I am using psutil for most of it and it is working fine except for one thing that I need. I'd like to log the average cpu wait time at the moment. from top output it would be in CPU…
nick_v1
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high load low cpu low iowait, why?

Look at the those peaks in the first graph, which factor can cause this? cpu 24X6
user1784472
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