---
title: profile_blockio
sidebar_position: 0
---

import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';

# profile_blockio

The `profile_blockio` gadget gathers information about the usage of the
block device I/O (disk I/O), generating a histogram distribution of I/O
latency (time), when the gadget is stopped.

Notice that the latency of the disk I/O is measured from when the call is
issued to the device until its completion, it does not include time spent
in the kernel queue. This means that the histogram reflects only the
performance of the device and not the effective latency suffered by the
applications.

The histogram shows the number of I/O operations (`count` column) that lie in
the latency range `interval-start` -> `interval-end` (`µs` column), which,
as the columns name indicates, is given in microseconds.

For this guide, we will use [the `stress` tool](https://man.archlinux.org/man/stress.1) that allows
us to load and stress the system in many different ways. In particular, we will use the `--io` flag
that will generate a given number of workers to spin on the [sync()
syscall](https://man7.org/linux/man-pages/man2/sync.2.html). In this way, we will generate disk I/O
that we will analyse using the `profile_blockio` gadget.

## Getting started

Running the gadget:

<Tabs groupId="env">
    <TabItem value="kubectl-gadget" label="kubectl gadget">
        ```bash
        $ kubectl gadget run ghcr.io/inspektor-gadget/gadget/profile_blockio:%IG_TAG% [flags]
        ```
    </TabItem>

    <TabItem value="ig" label="ig">
        ```bash
        $ sudo ig run ghcr.io/inspektor-gadget/gadget/profile_blockio:%IG_TAG% [flags]
        ```
    </TabItem>
</Tabs>

## Guide

Run the gadget in a terminal:

<Tabs groupId="env">
    <TabItem value="kubectl-gadget" label="kubectl gadget">
        ```bash
        $ kubectl gadget run profile_blockio:%IG_TAG% --node minikube-docker
        ```

        It will start to display the I/O latency distribution as follows:

        ```bash
        latency
              µs               : count    distribution
               0 -> 1          : 0        |                                        |
               1 -> 2          : 0        |                                        |
               2 -> 4          : 0        |                                        |
               4 -> 8          : 1        |*                                       |
               8 -> 16         : 21       |***************************             |
              16 -> 32         : 17       |*********************                   |
              32 -> 64         : 12       |***************                         |
              64 -> 128        : 0        |                                        |
             128 -> 256        : 0        |                                        |
             256 -> 512        : 0        |                                        |
             512 -> 1024       : 21       |***************************             |
            1024 -> 2048       : 3        |***                                     |
            2048 -> 4096       : 31       |****************************************|
            4096 -> 8192       : 0        |                                        |
            8192 -> 16384      : 0        |                                        |
           16384 -> 32768      : 0        |                                        |
           32768 -> 65536      : 0        |                                        |
           65536 -> 131072     : 0        |                                        |
          131072 -> 262144     : 0        |                                        |
          262144 -> 524288     : 0        |                                        |
          524288 -> 1048576    : 0        |                                        |
         1048576 -> 2097152    : 0        |                                        |
         2097152 -> 4194304    : 0        |                                        |
         4194304 -> 8388608    : 0        |                                        |
         8388608 -> 16777216   : 0        |                                        |
        16777216 -> 33554432   : 0        |                                        |
        33554432 -> 67108864   : 0        |                                        |
        ```

        Now, let's increase the I/O operations using the stress tool:

        ```bash
        # Start by creating our testing namespace
        $ kubectl create ns test-biolatency

        # Run stress with 1 worker that will generate I/O operations
        $ kubectl run --restart=Never --image=polinux/stress stress-io -n test-biolatency -- stress --io 1
        $ kubectl wait --timeout=-1s -n test-biolatency --for=condition=ready pod/stress-io
        pod/stress-io condition met
        $ kubectl get pod -n test-biolatency -o wide
        NAME        READY   STATUS    RESTARTS   AGE   IP           NODE          NOMINATED NODE   READINESS GATES
        stress-io   1/1     Running   0          2s    10.244.1.7   worker-node   <none>           <none>
        ```

        Using the profile block-io gadget, we can generate another histogram to analyse the
        disk I/O with this load:

        ```bash
        # Run the gadget again
        $ kubectl gadget run profile_blockio:%IG_TAG% --node minikube-docker
        latency
              µs               : count    distribution
               0 -> 1          : 0        |                                        |
               1 -> 2          : 0        |                                        |
               2 -> 4          : 0        |                                        |
               4 -> 8          : 786      |                                        |
               8 -> 16         : 57788    |****************************************|
              16 -> 32         : 39060    |***************************             |
              32 -> 64         : 1513     |*                                       |
              64 -> 128        : 36       |                                        |
             128 -> 256        : 16       |                                        |
             256 -> 512        : 260      |                                        |
             512 -> 1024       : 2045     |*                                       |
            1024 -> 2048       : 986      |                                        |
            2048 -> 4096       : 57       |                                        |
            4096 -> 8192       : 1        |                                        |
            8192 -> 16384      : 0        |                                        |
           16384 -> 32768      : 0        |                                        |
           32768 -> 65536      : 0        |                                        |
           65536 -> 131072     : 0        |                                        |
          131072 -> 262144     : 0        |                                        |
          262144 -> 524288     : 0        |                                        |
          524288 -> 1048576    : 0        |                                        |
         1048576 -> 2097152    : 0        |                                        |
         2097152 -> 4194304    : 0        |                                        |
         4194304 -> 8388608    : 0        |                                        |
         8388608 -> 16777216   : 0        |                                        |
        16777216 -> 33554432   : 0        |                                        |
        33554432 -> 67108864   : 0        |                                        |

        ```

        The new histogram shows how the number of I/O operations increased significantly.
    </TabItem>

    <TabItem value="ig" label="ig">
        ```bash
        $ sudo ig run profile_blockio:%IG_TAG%
        ```

        It will start to display the I/O latency distribution as follows:

        ```bash
        latency
              µs               : count    distribution
               0 -> 1          : 0        |                                        |
               1 -> 2          : 0        |                                        |
               2 -> 4          : 0        |                                        |
               4 -> 8          : 4        |                                        |
               8 -> 16         : 11       |**                                      |
              16 -> 32         : 1        |                                        |
              32 -> 64         : 10       |*                                       |
              64 -> 128        : 0        |                                        |
             128 -> 256        : 0        |                                        |
             256 -> 512        : 2        |                                        |
             512 -> 1024       : 11       |**                                      |
            1024 -> 2048       : 1        |                                        |
            2048 -> 4096       : 213      |****************************************|
            4096 -> 8192       : 0        |                                        |
            8192 -> 16384      : 0        |                                        |
           16384 -> 32768      : 0        |                                        |
           32768 -> 65536      : 0        |                                        |
           65536 -> 131072     : 0        |                                        |
          131072 -> 262144     : 0        |                                        |
          262144 -> 524288     : 0        |                                        |
          524288 -> 1048576    : 0        |                                        |
         1048576 -> 2097152    : 0        |                                        |
         2097152 -> 4194304    : 0        |                                        |
         4194304 -> 8388608    : 0        |                                        |
         8388608 -> 16777216   : 0        |                                        |
        16777216 -> 33554432   : 0        |                                        |
        33554432 -> 67108864   : 0        |                                        |
        ```

        Now, let's increase the I/O operations using the stress tool:

        ```bash
        $ docker run -d --rm --name stresstest polinux/stress stress --io 10
        ```

        Run the gadget to observe the I/O latency distribution:

        ```bash
        $ sudo ig run profile_blockio:%IG_TAG%
        latency
              µs               : count    distribution
               0 -> 1          : 0        |                                        |
               1 -> 2          : 0        |                                        |
               2 -> 4          : 0        |                                        |
               4 -> 8          : 202      |                                        |
               8 -> 16         : 13027    |*************************************   |
              16 -> 32         : 13833    |****************************************|
              32 -> 64         : 4272     |************                            |
              64 -> 128        : 876      |**                                      |
             128 -> 256        : 13       |                                        |
             256 -> 512        : 529      |*                                       |
             512 -> 1024       : 2913     |********                                |
            1024 -> 2048       : 720      |**                                      |
            2048 -> 4096       : 86       |                                        |
            4096 -> 8192       : 5        |                                        |
            8192 -> 16384      : 0        |                                        |
           16384 -> 32768      : 0        |                                        |
           32768 -> 65536      : 0        |                                        |
           65536 -> 131072     : 0        |                                        |
          131072 -> 262144     : 0        |                                        |
          262144 -> 524288     : 0        |                                        |
          524288 -> 1048576    : 0        |                                        |
         1048576 -> 2097152    : 0        |                                        |
         2097152 -> 4194304    : 0        |                                        |
         4194304 -> 8388608    : 0        |                                        |
         8388608 -> 16777216   : 0        |                                        |
        16777216 -> 33554432   : 0        |                                        |
        33554432 -> 67108864   : 0        |                                        |
        ```
    </TabItem>
</Tabs>

You can clean up the resources created during this guide by running the following commands:

<Tabs groupId="env">
    <TabItem value="kubectl-gadget" label="kubectl gadget">
        ```bash
        $ kubectl delete ns test-biolatency
        ```
    </TabItem>

    <TabItem value="ig" label="ig">
        ```bash
        $ docker rm -f stresstest
        ```
    </TabItem>
</Tabs>

## Exporting metrics

The `profile_blockio` gadget can expose the histograms it generates to a
Prometheus endpoint. To do so, you need to activate both the metrics listener as
well as the gadget collector. To enable the metrics listener, check the
[Exporting Metrics](../reference/export-metrics.mdx) documentation. To enable
the collector for the `profile_blockio` gadget with the metrics name
`blockio-metrics`, run the following command:

<Tabs groupId="env">
    <TabItem value="kubectl-gadget" label="kubectl gadget">
        ```bash
        WIP: Headless mode for kubectl gadget is under development
        ```
    </TabItem>

    <TabItem value="ig" label="ig">
        ```bash
        gadgetctl run ghcr.io/inspektor-gadget/gadget/profile_blockio:%IG_TAG% \
                    --annotate=blockio:metrics.collect=true \
                    --otel-metrics-name=blockio:blockio-metrics \
                    --detach
        ```
    </TabItem>
</Tabs>

<Tabs groupId="env">
    <TabItem value="kubectl-gadget" label="kubectl gadget">
        ```bash
        WIP: Headless mode for kubectl gadget is under development
        ```
    </TabItem>

    <TabItem value="ig" label="ig">
        Unless you configured the metrics listener to do differently, the
        metrics will be available at `http://localhost:2224/metrics` on the
        server side. And for the `profile_blockio` gadget we ran above, the
        metrics will be available under the `blockio-metrics` scope:

        ```bash
        $ curl http://localhost:2224/metrics -s | grep blockio-metrics
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="1"} 0
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="2"} 0
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="4"} 0
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="8"} 10
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="16"} 193
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="32"} 374
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="64"} 943
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="128"} 1825
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="256"} 2829
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="512"} 3905
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="1024"} 4280
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="2048"} 4351
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="4096"} 4351
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="8192"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="16384"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="32768"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="65536"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="131072"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="262144"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="524288"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="1.048576e+06"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="2.097152e+06"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="4.194304e+06"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="8.388608e+06"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="1.6777216e+07"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="3.3554432e+07"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="6.7108864e+07"} 4354
        latency_bucket{otel_scope_name="blockio-metrics",otel_scope_version="",le="+Inf"} 4354
        latency_sum{otel_scope_name="blockio-metrics",otel_scope_version=""} 1.520032e+06
        latency_count{otel_scope_name="blockio-metrics",otel_scope_version=""} 4354
        otel_scope_info{otel_scope_name="blockio-metrics",otel_scope_version=""} 1
        ```
    </TabItem>
</Tabs>

Finally, stop metrics collection:

<Tabs groupId="env">
    <TabItem value="kubectl-gadget" label="kubectl gadget">
        ```bash
        WIP: Headless mode for kubectl gadget is under development
        ```
    </TabItem>

    <TabItem value="ig" label="ig">
        ```bash
        $ gadgetctl list
        ID           NAME                                                      TAGS                                                      GADGET
        3e68634c4c28 amazing_payne                                                                                                       ghcr.io/inspektor-gadget/gadget/profile_blockio:latest
        ```

        ```bash
        $ gadgetctl/... delete 3e68634c4c28
        3e68634c4c28a981a60fe96a29d24a99
        ```
    </TabItem>
</Tabs>
