Questions tagged [io]

I/O is an acronym for input/output, which refers to the mechanism or process for the transfer of information between one system or component and another.

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GNU parallel: why does diagnostic output look like sequential execution rather than parallel execution?

Scenario: $ cat libs.txt lib.a lib1.a $ cat t1a.sh f1() { local lib=$1 stdbuf -o0 printf "job for $lib started\n" sleep 2 stdbuf -o0 printf "job for $...
pmor's user avatar
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Running a screensaver on top of console program after inactivity: how to watch for input?

I'm implementing a screensaver system that would wait for user input on a tty, and, in the event that it didn't get any, would play a screensaver until input is received. How would I efficiently tap ...
R-Rothrock's user avatar
2 votes
1 answer
65 views

How can a different controller explain this I/O?

My new NAS has 5 disks. They are all same model. sde is connected to the controller on the motherboard. sda-sdd is on the raid controller. Run 'pv /dev/sd[cde]' in parallel: Device rkB/s wkB/...
Ole Tange's user avatar
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How to tune BFQ schduler to prevent a single low priority process from severely degrading system performance?

I have been trying to use nice/ionice for a while and it turns out that bfq ignores ionice parameters. So how do I prevent a low priority process from consuming all the io bandwith to the detriment of ...
Morrison's user avatar
1 vote
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112 views

Determining system's unresponsiveness when high IO load

I'm trying to understand why my Fedora 38 (KDE on Wayland) becomes unresponsive for some seconds while there's high IO on the root disk (a SanDisk SSD PLUS 240GB (UF5000RL)). The root partition is ...
TesX's user avatar
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how to check if the IO was hanging

Are there any method I could use in centos to check if the block device under the IO was hanged? I tried to check the /proc/diskstats, but it is not obvious enough to show if there is an hang there. ...
lei wang's user avatar
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FIO reports slower sequential read than the advertised NVMe SSD read bandwidth

TLDL For the very simple sequential read, FIO reports is much slower than the NVMe SSD sequentail read capability. Main Text Hello everyone, I have been facing an issue while trying to achieve the ...
JGL's user avatar
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Calculating the CPU-utilization given a round-robin scheduler with 1 ms time quantum, CPU-bound and I/O-bound tasks, and a context-switch time penalty

Consider a system running ten I/O-bound tasks and one CPU-bound task. Assume that the I/O-bound tasks issue an I/O operation once for every millisecond of CPU computing and that each I/O operation ...
NoName123's user avatar
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Latency on pselect caused by other user space processes

I have the following pre-condition on Linux: I'm using a process to read serial data using pselect on a serial device /dev/ttySX. Data comes in at a stable frequency of 400 Hz. To optimize latency of ...
nyquist's user avatar
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How to use vdbench to do multiple operations concurrently on the 3 file system

I want to use following vdbench parameter files to do muliple operations concurrently on the 3 file system, however, the execute failed as in below. Can some one help to check what is wrong in the ...
lei wang's user avatar
2 votes
1 answer
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Softirq delayed because of the Heavy I/O Operation

I am trying to copy the contents of a 1 GB ISO file (stored in USB) to my internal storage. As part of a test when i am doing repetitive copy operation from USB to my hard drive continuously I observe ...
Eswar Reddy's user avatar
3 votes
1 answer
227 views

I/O errors, but after running badblocks everything works again : how is that possible?

TLDR; HDD seemed damaged. Unable to format partition (mkfs.ext4 I/O errors), even with a newly created GPT table. SMART test shows some errors. I was about to throw the disk away. Before that, out of ...
ChennyStar's user avatar
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Dmesg reports a lot of "Unrecovered read errors" and yet rsync copies just fine. Why?

I've been copying moderately valuable data (nice to have, not the end of the world if it is lost) from a bunch of old HDDs to my new NAS with more reliable storage. During reading I get a bunch or ...
Joachim Sauer's user avatar
2 votes
1 answer
214 views

Force rsync to output messages line-by-line

(I'm not sure if this question should go on StackOverflow or here. But the actual problem is with rsync, so on balance I reckon it's a Linux question. If admins disagree, by all means please migrate ...
Sod Almighty's user avatar
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Linux socket modes of IO

There are three modes of i/o. They are Programmed IO, Interrupt IO and DMA. My understanding is, Programmed IO requires CPU to busy-wait while Interrupt IO by nature, is ansynchronous. Where can I ...
cpp's user avatar
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mc command hangs with --version parameter when writing to stdout but works when piping to cat?

I observed odd behaviour of a utility binary (it's actually the minio client mc in a recent-ish version) when running it from the command line. If I just run it like ./mc --version, the command hangs ...
BMBM's user avatar
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time difference of rm single tar file between large and small size

If I have a file data.tar and one is 1 MB in size versus one that is 10 GB in size versus one that is 10.0 TB in size (yes 10 terabytes is correct) why is there a time difference in doing a rm on ...
ron's user avatar
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Enable IO accounting inheritance in the Linux kernel only for specific applications

The Linux kernel does IO accounting, it calculates how many pages of data the process has read and written (IO_READ/IO_WRITE). Here's the issue: when an application launches another application which ...
Artem S. Tashkinov's user avatar
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Need help debugging slow NFS with high avg RTT on Ubuntu

I'm managing a number of libvirt hypervisors, where the VMs data is stored on a NFS server. I've been experiencing high I/O wait on the hypervisors' CPUs, and as such decided to dig a little deeper. ...
Ian Falatik's user avatar
2 votes
1 answer
407 views

How to disable/enable bounce-buffers in IOMMU?

I am trying to figure out how to disable bounce buffers used in IOMMU when the hardware IOMMU is used. To give more context, when IOMMU_DEFAULT_DMA_STRICT is set in the kernel it enables strict IOTLB ...
sammy17's user avatar
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Parallelism and I/O in Linux

I'm a bit confused about how the Linux kernel handles parallelism during I/O operations (if it handles it at all). I assume it can concurrently operate on file descriptors, but does it achieve ...
asnail's user avatar
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Oracle Linux 8.x - Performance Test (Stress / Load / IO / Network Usage / Memory Usage)

I want to do performance test on Oracle Linux 8 KVM guest server (It will be used as Application server (WLS 14c) and/or Oracle DB server). What are the best tools I can provide this with? I saw an ...
rndm_acct1's user avatar
1 vote
1 answer
497 views

How to monitor the I/O of a network-mounted disk in a process specific manner?

We have a disk mounted via network. nfsiostat revealed some basic stats for the whole disk: $ sudo nfsiostat -d /mountpoint 10.20.xxx.xx:/source mounted on /mountpoint: op/s rpc bklog 7.01 ...
Jerry Fan's user avatar
3 votes
1 answer
1k views

How does mmio get routed to io devices?

I am trying to understand how IO devices are mapped into the 'regular' memory address space on modern x86 machines running Linux. Some details which I am trying to make sense of are: cat /proc/iomem ...
shafe's user avatar
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60 views

Monitoring disk IO on MTD devices

Is there a tool for monitoring disk IO on MTD devices? I'm using UBI on top of MTD, so could also monitor IO there if that's possible. It seems like only an erase counter is available in UBI and ...
andrey's user avatar
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1 answer
242 views

What makes sfill so slow?

sfill -Illv makes a file with data from /dev/urandom until it fills the partition. Making a large file like this takes a lot of time. iotop tells me it is writing about 1 MB/s. Though dd if=/dev/...
xkehz's user avatar
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1 answer
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bash IO redirection, how du dup() STDERR?

Consider the following example: exec 10>&2 # duplicate STDERR to fd 10 { echo ok; inexistantcommand; } > /tmp/both 2>&1 10>/tmp/err exec 10>&- # close fd 10 I expect /tmp/...
Mévatlavé Kraspek's user avatar
2 votes
1 answer
128 views

bash IO redirection with tee, without complicated syntax, how it works?

One way to do implicit dup(2) in bash with the output in fd {10,11,12} in a real use-case and close it right after, based on this: $ cat tags desktop-19.9.0 foobar-1.2.3 desktop-22.9.0 mobile-24.10.0 ...
Gilles Quénot's user avatar
1 vote
1 answer
159 views

Bash IO redirection, open & close 'fd', can someone explain?

I try to understand this concept for years, with at this time some incomplete knowledge of this. Is anyone here can make a kind of a tutorial or good explanations with examples on how to open a new ...
Mévatlavé Kraspek's user avatar
0 votes
0 answers
102 views

Gparted enable more logging

I cannot find a way for Gparted to produce more informative logs in the manual. What I am looking for is to find out why exactly did e cartain I/O operation fail (more details about the SCSI command ...
Łukasz Przeniosło's user avatar
1 vote
1 answer
345 views

cgroup v2 io.max limit not applied

I can't seem to be able to apply io.max limit through cgroups v2 on Rocky Linux 9. Setup: # lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS ... ├─nvme0n1p5 259:5 0 444.9G 0 part │ └─...
mike's user avatar
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763 views

How to get disk I/O activity by files and processes?

On Red Hat 8 I sometimes get huge disk I/O operations. I can see disk I/O activities by using sudo iotop -oP command. Output is: PID | USER | DISK READ | DISK WRITE ---- ------ ----------- ----------- ...
folow's user avatar
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1 answer
1k views

Isolating I/O issue with NVME or hardware?

Hardware: Samsung 980 PRO M.2 NVMe SSD (MZ-V8P2T0BW) (2TB) Beelink GTR6, with the SSD in the NVMe slot Since the hardware arrived, I've installed Ubuntu Server on it as well as a bunch of services (...
Tiago's user avatar
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2 votes
0 answers
391 views

Is there a GUI linux application that shows per mounted disk i/o transfer rate in a graphic?

Is there a GUI linux application that shows per mounted disk i/o transfer rate in a graphic? (Like gnome-system-monitor do for the swap mount but for each mounted drive) I'm looking for an application ...
user avatar
1 vote
0 answers
97 views

host hangs after cat /dev/null > bigfile.log

I found a big log file(2.7 TB) on my disk, so I decided to empty it with the following command: cat /dev/null > bigfile.log After I executed this cmd, I lost my ssh connection. When I logged in ...
Cans Fong's user avatar
2 votes
1 answer
42 views

input redirection to common commands like userdel [duplicate]

Is it possible to use users.txt a file that contains some users to redirect the input to userdel like this userdel < users.txt my question applpies to these common commands not only userdel.
Hussam Elshehawy's user avatar
1 vote
1 answer
950 views

What is the impact of different Linux I/O APIs on performance benchmarking of NVMe SSDs? (libaio vs SPDK vs io_uring)

I am benchmarking NVMe SSDs on my Linux server, with the aim to achieve the IOPS, BW and Latency values as mentioned in the product specifications. I'm using FIO as workload generator, and used libaio ...
Jaideep Khare's user avatar
1 vote
1 answer
192 views

How to write a one-page file to disk in one flush?

Say I have 4096 bytes of data that I want to save in a file. It should take exactly one page and can be flushed only once. However, if I do it using multiple calls to kernel i.e. write piece by piece, ...
donaastor's user avatar
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0 answers
153 views

in linux, system is slowed very much and CPU 100% when I copy from (non-system-based) usb HDD to another usbHDD. Why?

in linux, system is slowed very much and CPU 100% when I copy from (non-system-based) usb HDD to another usbHDD. Why? My CPU is 100%. I was told that CPU can be 100% without system be slowed down....
Estatistics's user avatar
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1 answer
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Soft link will pass filename as 1st parameter to target?

https://github.com/adurbin/iotools Original usage is: ./iotools rdmsr x xxxxx when I doing: ln -sf iotools rdmsr then I can do: rdmsr x xxxxx Why?? because when doing soft linking, it will pass the ...
Mark K's user avatar
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-1 votes
2 answers
51 views

When io util is relatively high, will Linux read and write hard disks return EIO?

When input/output util is relatively high, will Linux read and write hard disks return EIO?
yangfan's user avatar
1 vote
0 answers
103 views

why top command in linux shows high us and low wa while cp many large files simultaneously?

I am copying 10 large files(which may costs 1 hour) simultaneously, and I used top command to check the cpu usage, but I found out 100.0 us and 0.0 wa. shouldn't it be IO-bound instead of CPU-bound? I ...
cluuuuu's user avatar
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0 votes
1 answer
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Why top is not reporting high %wa on too many write sys calls

My HTTP application suddenly started taking extra time to start up. During this phase, it loads the data from the disk to the in-memory data structure. I doubt it is due to the extensive logging ...
shubmishra's user avatar
1 vote
1 answer
584 views

Is it possible to disable page caching on Ubuntu?

I am running an application on Ubuntu 20.04 which requires me to clear the page cache everytime I run it. Currently, I just run echo 1 | sudo tee /proc/sys/vm/drop_caches everytime before I run the ...
Sathvik Swaminathan's user avatar
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0 answers
363 views

Determine DISK IO for a specific process in linux

I have an application that I am working on a sorting algorithm for a large data set. I want to calculate the effect of I/O in this algorithm. Does counting the number of reading and writing operations ...
tuasopsdk's user avatar
2 votes
1 answer
293 views

SSD performance different results in dd and gnome-disk

I wanted to measure my SSD read/write performance and found some recommendations for using dd and gnome-disks. (from my understanding, hdpart is not relevant since it's not using the disk itself but ...
hutcruchi's user avatar
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0 votes
1 answer
173 views

How does the --bsize option in fio work?

Since fio is a benchmarking tool that for each run, should simulate a real I/O workload, how does the --bsize option fit with that? My understanding is that the filesystem has a set block size for ...
Macondoman's user avatar
1 vote
1 answer
689 views

Why not always use 'oflag=direct' in 'dd'?

Using oflag=direct in dd seems always to make operations much faster than either not using it, or using pv etc. to do the operation instead. Under what circumstances might I not want to use oflag=...
EmmaV's user avatar
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-1 votes
1 answer
552 views

How to access virtual address via terminal in Ubuntu?

i'm trying to read & write to register by using the busybox devmem command. I printed its base address from the driver's source code and received the following address: 0xffffff800bdd0000 I ...
jetson user's user avatar
0 votes
1 answer
397 views

Debian 11 - How can i lower the load on my server?

I'm currently running a Debian 11 with a load average of 4. I want to lower this load - But i don't really know where to start, like a first step on at least the analisis part... It's a Docker Server, ...
Raul Chiarella's user avatar

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