DICOM-WEB: study downloading eats all CPU

Plugins: dicomweb, mysql for index, s3 for storage
Study: 6.5Gb, 3100 instances

GET dicom-web/studies/{StudyInstanceUID} works for 90 seconds and eats all CPU during this request.

90 seconds is ok, but why is it so CPU intensive? Any ideas on how to fix it?

What version of Orthanc are you using?
It might be due to ChunkedTransfers set to true if you’re using Orthanc 1.5.7 or 1.5.8.
See https://book.orthanc-server.com/plugins/dicomweb.html?highlight=ChunkedTransfers and https://bitbucket.org/sjodogne/orthanc/issues/156/

Besides, good practice is to provide minimal work example to reproduce your issue instead of just guessing as I did now…

I used latest Orthanc from mainline.

Also just reproduced on with latest jodogne/orthanc-plugins (using only dicomweb plugin). So it’s not a s3 plugin issue.
Downloading 6.5Gb study with 3100 instances takes 2-3 minutes and uploading is really slow to. Also CPU load is 300% during this process on my macbook pro 2019.

Looks like disabling ChunkedTransfers doesn’t change anything.

Hello,

It is important to uncouple the possible sources when investigating any problem.

As a consequence, first of all, please disable the S3 plugin and the MySQL plugin (i.e. use the barebone SQLite database, that is just fine for 3100 instances). They might be the source of the high CPU usage.

Then, try again and see if this improves performance.

If not, please provide the exact command lines you use (how you start Orthanc and the curl commands):
https://book.orthanc-server.com/users/support.html#discussing-a-minimal-working-example

Sébastien-