Description of problem:
The hd performance of Fedora 16 3.1 rc kernel is ca. 50% that of Fedora 15
Here's the hdparm output:
Timing cached reads: 1396 MB in 2.00 seconds = 698.33 MB/sec
Timing buffered disk reads: 180 MB in 3.02 seconds = 59.66 MB/sec
Timing cached reads: 984 MB in 1.99 seconds = 494.18 MB/sec
Timing buffered disk reads: 84 MB in 3.09 seconds = 27.20 MB/sec
This is consistent.
Also, the resume from hibernation takes twice to three times longer than with Fedora 15
Version-Release number of selected component (if applicable):
About as fast as Fedora 15
I couldn't find anything with my google-fu, hope this is appropriate, I intentionally set the priority to low
f16 kernels still have all of the kernel debugging options enabled whereas f15 does not. Before we go worrying about performance issues, we should test on a kernel that has the debug stuff turned off. We already know those options significantly slow down Xorg as well.
The next f16 kernel build should have them off. I'll post a URL to it here for testing.
Great, thanks. I was expecting something along these lines, just not such a huge impact. Will wait and test.
I've started a 3.1-rc6 build that has the debugging options disabled. You can test this build when it completes:
thanks, this brings hard disk performance back at expected levels. More thorough tests will have to wait, as I have on of those "nice" netbooks from acer with a brcm4312 chip, which has to use the brcmsmac driver.
Thanks for testing. I'll put this in MODIFIED state for now.
kernel-3.1.0-0.rc6.git0.0.fc16 has been submitted as an update for Fedora 16.
Can we look at fixing this for f17 kernels as well? For now, I have just rebuilt an f17 kernel using the f16 config files. This is a pain to do, but things are so much slower with debugging enabled that I am losing so much time waiting for stuff to happen (kernel builds, yum updates) that run alternative kernels is the best answer for me now.
I don't know if this affects things, but in my case I am running dmcrypt on top of mdraid.
see comment 32 of bug 735268
kernel-3.1.0-0.rc6.git0.0.fc16 has been pushed to the Fedora 16 stable repository. If problems still persist, please make note of it in this bug report.