Bug #56537: cephfs-top: wrong/infinitely changing wsp values - CephFS - Ceph

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Bug #56537

closed

cephfs-top: wrong/infinitely changing wsp values

Added by Jos Collin almost 2 years ago. Updated over 1 year ago.

Status:

Resolved

Priority:

Normal

Assignee:

Jos Collin

Category:

Correctness/Safety

Target version:

Ceph - v18.0.0

% Done:

Source:

Tags:

backport_processed

Backport:

pacific,quincy

Regression:

Severity:

3 - minor

Reviewed:

Affected Versions:

ceph-qa-suite:

Component(FS):

cephfs-top

Labels (FS):

Pull request ID:

47099

Crash signature (v1):

Crash signature (v2):

Description

wsp(MB/s) field in cephfs-top shows wrong and negative values changing infinitely.

Steps to reproduce:
1. Create two filesystems and mount them as client1 and client2.
2. run cephfs-top.
3. Write something to client1 only.
4. Both client1 and client2 shows changing wsp values, even if there is no IO in client2.

client1 shows changing positive values and client2 shows changing negative values. This continues infinitely since the write starts and doesn't stop when the write ends. However, this issue is not observed in 'perf stats' output.

Related issues 2 (0 open — 2 closed)

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Updated by Venky Shankar almost 2 years ago

Jos Collin wrote:

wsp(MB/s) field in cephfs-top shows wrong values when there is an IO.

Steps to reproduce:
1. Create two filesystems and mount them as client1 and client2.

userland or kclient?

2. run cephfs-top.
3. Write something to client1 only.
4. Both client1 and client2 shows changing wsp values, even if there is no IO in client2.

There can be little variance, but not huge if there is no IO.

client1 shows changing positive values and client2 shows changing negative values. This continues infinitely since the write starts and doesn't stop when the write ends.
However, this issue is not observed in 'perf stats' output.

So, I think this is a bug in fstop and not in client/mds?

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Updated by Jos Collin almost 2 years ago

Venky Shankar wrote:

Jos Collin wrote:

wsp(MB/s) field in cephfs-top shows wrong values when there is an IO.

Steps to reproduce:
1. Create two filesystems and mount them as client1 and client2.

userland or kclient?

both

2. run cephfs-top.
3. Write something to client1 only.
4. Both client1 and client2 shows changing wsp values, even if there is no IO in client2.

There can be little variance, but not huge if there is no IO.

As I understand, wsp(MB/s) should come to 0 when the IO ends? But it never comes to 0. The client2 goes negative too. This happens probably because the `size` variable used to calculate the wsp value doesn't reset when there's a new client.

client1 shows changing positive values and client2 shows changing negative values. This continues infinitely since the write starts and doesn't stop when the write ends.
However, this issue is not observed in 'perf stats' output.

So, I think this is a bug in fstop and not in client/mds?

Yes, it's a bug in cephfs-top.

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