** Changed in: linux (Ubuntu)
Status: New => Fix Released
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https://bugs.launchpad.net/bugs/653611
Title:
extremely bad dm-crypt latency
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Seems like I should have been testing 2.6.38-rc2 better. I checked a few
days ago, benchmarked and tought I had forgotten to revert the patch.
Went back to 2.6.37, because standby on my machine is broken with in
2.6.38. Just compiled a pristine mainline 2.6.38-rc2 to be sure and it
really seems fix
There is a bit progress, you can read the details at http://www.linux-
archive.org/device-mapper-development/474248-problem-ssd-access-time-dm-
crypt-way-too-high.html. There are currently two patches, which
completely resolve the issue for me, but have their own problems and
presumably won't go in
Note that listing all files with find (exact commandline see below) is
34 times faster on 2.6.32 (367s vs 10.7s).
# echo 1 > /proc/sys/vm/drop_caches
# time find / > /dev/null
** Attachment added: "LatencyTOP information about find, while listing all
files on the root partition with 2.6.32 (10.7
** Attachment added: "LatencyTOP information about find, while listing all
files on the root partition with 2.6.35 (367 seconds)"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/653611/+attachment/1666559/+files/latencytop-find-2.6.35.png
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extremely bad dm-crypt latency
https://bugs.
Note the huge difference in the amount of context-switches.
** Attachment added: "vmstat output during the palimpsest benchmark under
2.6.32"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/653611/+attachment/1666558/+files/vmstat-palimpsest-2.6.32.txt
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extremely bad dm-crypt latency
Ignore the performance spikes, these are caused by empty space, which the
firmware of the drive handles faster.
Comparing the encrypted disk (2.6.32) with the raw disk, there seems to be
virtually no performance penalty.
** Attachment added: "Raw disk benchmarked under 2.6.32, 0.2ms latency"
** Attachment added: "vmstat output during the palimpsest benchmark under
2.6.35"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/653611/+attachment/1666557/+files/vmstat-palimpsest-2.6.35.txt
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extremely bad dm-crypt latency
https://bugs.launchpad.net/bugs/653611
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** Attachment added: "Encrypted disk benchmarked under 2.6.32, 0.2ms latency"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/653611/+attachment/1666554/+files/latencytop-find-2.6.32.png
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extremely bad dm-crypt latency
https://bugs.launchpad.net/bugs/653611
You received this bug notif
** Attachment added: "Encrypted disk benchmarked under 2.6.35, 10.1ms latency"
https://bugs.launchpad.net/bugs/653611/+attachment/1666553/+files/palimpsest-2.6.35.png
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extremely bad dm-crypt latency
https://bugs.launchpad.net/bugs/653611
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Public bug reported:
The latency induced by dm-crypt seems to have increased at least five-fold with
the Maverick 2.6.35 kernel, compared to the Lucid 2.6.32 kernel.
This makes a very fast SSD system feel like slower than with an HDD.
I did some benchmarks from my current Lucid install with stock
Extremely annoying bug, happend with hardy, intrepid and jaunty.
Current Configuration:
- Jaunty x64
- Intel(R) Core(TM)2 Duo CPU T7300 @ 2.00GHz, 4GiB DDR2
- Encrypted Home (--cipher aes-xts-plain --key-size 256)
- kernel.org custom 2.6.30 kernel
I simulate a write load (like copying large
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