Why OneDrive slowed under Linux

For several months, users of OneDrive for Business complain of a strange problem: the web application opens very slowly and works slowly under Linux (Chrome / Firefox). But the speed of the application increases dramatically if you change the user-agent on Windows.

November 26, 2016, one of the users gave such an example. On Ubuntu / Linux 16.04 + Chrome / Firefox (latest version) it opens:

https://<my_company>-my.sharepoint.com/personal/<my_user>/_layouts/15/onedrive.aspx

Within two minutes, the UI does not respond, the CPU load is 100%, the network panel shows a page load of about 100 MB.
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If you change the user-agent in the browser, specifying the Windows operating system, then everything works as expected.

In the following discussion, the problem was confirmed by other users. Some were frustrated with Microsoft’s behavior, one said about switching to Google Apps. At this discussion and stopped. As it turned out, it is difficult to get justice in the official support forum.

The topic resurfaced on March 22, 2017, when one of the Reddit users complained about a similar problem. He said that he uses a laptop with Linux Mint 18.1 and Firefox 52, and uses only Word from Office 365 services. This has to be done, because when working in a team, format compatibility is important. Unlike the previous user, his OneDrive still runs, although it works very slowly, with creepy lags. At the same time, there are no such problems on the Windows 10 desktop computer.

Then he got the idea to try the extension to change the user-agent in Firefox. He put such a user-agent, changing only the operating system: Mozilla / 5.0 (Windows NT 6.1; WOW64; rv: 40.0) Gecko / 20100101 Firefox / 52 - and the problem was miraculously solved. The OneDrive interface did not slow down at all.

The user said that the same method helped his friend. If you return the usual Mozilla / 5.0 user-agent (Linux Mint / 18.1; WOW64; rv: 40.0) Gecko / 20100101 Firefox / 52, the brakes are also returned.

The strange behavior of the web application has generated a number of questions. It is not clear how application performance may depend on user-agent?

March 23, 2017, Microsoft finally clarified the situation . The employee explained that this bug was fixed. It turns out that the problem was with the StaticLoad.aspx page, which in the background pumps up resources for office web applications (this is the standard optimization technology in browsers - prefetching or prefetching).

As it turned out, due to ridiculous chance, this page used one link for prefetching in browsers on iOS, Chrome OS, Mac, Windows operating systems, but for browsers on Linux operating system, it slid into an alternative, less efficient prefetch mechanism - without optimization.

The employee stressed that the problem was fixed on March 22 at 15:00 PST, it was a completely unintentional mistake - and apologized for any inconvenience.

In a more detailed explanation , a Microsoft employee explained that by a “less efficient” prefetching mechanism, he means prefetching using the <object>, <script>, <img> tags. In this case, prefetch links are not used. This is the mechanism that browsers under Linux have been switching to.

The employee said that browser recognition by the StaticLoad.aspx page was done to select the prefetch method, because not all browsers support the most optimal prefetching of links. Therefore, some were rolled into the prefet through tags <object>, <script>, <img>.

Perhaps there was some kind of white or black list - and this list did not work completely correctly. Well, such simple programmer errors occur even in large companies like Microsoft. The main thing is that the company, albeit with a delay of six months or a year, but recognized the problem - and corrected it.

"Updated" Microsoft declares that it is very friendly with Open Source and GNU / Linux. Everyone remembers how Satya Nadella said : “Microsoft loves Linux”. True, this does not prevent Microsoft from continuing to patent attacks on Linux and issue money with Android , but these are trifles.