[dm-crypt] Computer locking up on heavy disk IO

Michael Kjörling michael at kjorling.se
Tue Aug 1 22:47:36 CEST 2017


On 1 Aug 2017 22:22 +0200, from heinrich5991 at gmail.com:
> Aug 01 22:05:27 kernel: ata_piix 0000:00:1f.2: swiotlb buffer is full (sz: 61440 bytes)
> Aug 01 22:05:27 kernel: ata_piix 0000:00:1f.2: DMA: Out of SW-IOMMU space for 61440 bytes

I think that's the key. Don't know why it'd only affect usage through
dm-crypt, though.

[1] isn't about the exact same issue (that's someone getting very
similar errors with a network card) but suggests booting with
iommu=force or even iommu=off causes the errors to go away. It'll
likely kill performance, but it seems like a good test. If the system
is stable with such a configuration, one might expect that the drive
itself doesn't have any problems with the usage.

Also, there seem to be lots of reports that this happens with kernels
3.8.0 and newer, but that 3.7.x and earlier don't exhibit the same
problem and [2] says a fix for another similar issue may be in 3.8.3
or possibly (as per [3]) 3.8.4. Which of course prompts the question:
what kernel version are you running? And while you're at it, you might
also tell us which cryptsetup version you're running; while I really
doubt this is cryptsetup related, that piece of information can hardly
hurt.

And [4] suggests increasing the swiotlb size using the swiotlb=N
kernel parameter, where N apparently is the number of 2 KiB blocks to
allocate (65536 for 128 MB, 131072 for 256 MB). That feels like a
stopgap measure, though, even more so than disabling IOMMU, but if all
else fails...


 [1]: https://bbs.archlinux.org/viewtopic.php?pid=650269#p650269

 [2]: https://forum.siduction.org/index.php?topic=3272.msg27986#msg27986

 [3]: https://forum.siduction.org/index.php?topic=3272.msg28451#msg28451

 [4]: https://www.spinics.net/lists/linux-ide/msg25119.html

-- 
Michael Kjörling • https://michael.kjorling.semichael at kjorling.se
                 “People who think they know everything really annoy
                 those of us who know we don’t.” (Bjarne Stroustrup)


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