A major bug related to the display of attachments has been fixed. An immediate improvement in performance has been measured (via CPU resources) and observed.

Image heavy threads are quick as lightning now. Thanks admin!

Was this the issue where attachment thumbnails needed to be regenerated per request?

It was a horrendous arrangement -- attachment.php, which deals with everything attachment-related, was executed for each and every thumbnail displayed to a user. Attachment.php contains 150 lines of code and queries the database multiple times. This script was being triggered thousands of times at a given time.

I spent so much time trying to circumvent this issue and it's finally fixed. The array that's loaded by the script handling threads is used to determine thumbnail image paths instead of executing attachment.php to then query the database to then determine the path of the thumbnail image.

Crazy design oversight for this version of MyBB; crazy inefficient. I just assumed it was mostly my internet to blame, and didn't fully appreciate how bad it really was. Glad you found a fix though.

Seems to be running well now

Thanks sbflicker! This issue has consumed a great deal of our time and energy (managing server performance) -- we're now free to make some fundamental improvements in the area of design and function (batch uploads being key).

Wow! Dramatic improvement. Some threads were still not loading after many minutes, and now they're filling as fast as the thumbnails can be sent.

>attachment.php, which deals with everything attachment-related, was executed for each and every thumbnail displayed to a user.

Holy fuck. No wonder the site was strangled.

(July 1, 2016, 1:26 pm)ghoolihan >attachment.php, which deals with everything attachment-related, was executed for each and every thumbnail displayed to a user.

Holy fuck. No wonder the site was strangled.

Absolutely. It's something I tried resolving by tinkering with elements of the script and eventually abandoned. After reaching out to the developers of MyBB, I was told that (a) it's not an issue or (b) it's not practical to address. In returning to some of my old threads, I discovered that my complaint had been flagged and incorporated into official development plans for MyBB 1.8 and MyBB 2.0 -- importantly, one of the key developers provided a very simple fix (which I didn't realize was possible and no one else suggested).

Nice job! It's like a whole new site now!