LWN.net Logo

Huge pages, slow drives, and long delays

Huge pages, slow drives, and long delays

Posted Nov 25, 2011 7:33 UTC (Fri) by set (guest, #4788)
Parent article: Huge pages, slow drives, and long delays

Well, just a comment as a desktop user that had no trouble reproducing this problem:

I have a usb stick which has poor write speed, which I periodicly copy ~16gb of linear data to. If I just left the machine alone, it would struggle along at a rate of perhaps 1mb/s - 3mb/s, with occasional pauses where almost no data moved. If, however I were to try and use a browser, not only would the browser hang for upto minutes, but other applications would hang, not updating their windows, AND the copy process really went to hell, trickling out a few kb/s and requiring hours to complete. Oddly, the only way I could get things going again after it entered this IO hell state, was to just cat gigs of disk files. (this just got the copy going again-- no help for hanging applications.)

This seems the definition of unacceptable behaviour on what is an otherwise capable dual core amd64 box with 4gb of ram. Eventually, after trying many things to tune swap/page and even formating the USB sticks to start their data clusters on 128k clusters, etc. (before that, the IO was even slower...) I finally just rebuilt the kernel without transparent huge pages. I wish I had heard they might be at fault earlier, but for me that was just a guess.

So, unless some fix is implemented, it would seem to me that transparent huge pages is simply an option that should at least be documented as being potentially completely destructive to desktop usage.


(Log in to post comments)

Huge pages, slow drives, and long delays

Posted Nov 25, 2011 19:45 UTC (Fri) by jospoortvliet (subscriber, #33164) [Link]

What I wonder if this can also hit you on a internal SSD which has performance issues... My system stalls frequently like this when an app tries to allocate memory.

Huge pages, slow drives, and long delays

Posted Nov 29, 2011 9:21 UTC (Tue) by Thomas (subscriber, #39963) [Link]

Exactly the same behaviour here on my laptop at work with a 32GB SD-card connected via a built-in MMC/SD-card reader. After having written more than 8GB of a 16GB git repository via rsync to the SD card, I have lock-ups for minutes (system load > 8 according to xosview). I have to try out and disable this huge pages feature and try again.

Thanks to Jonathan for the very enlightening article!

Copyright © 2013, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds