New: [BUG] bad performance and system stalls when using dm-crypt

https://bugzilla.kernel.org/show_bug.cgi?id=18302

Summary: [BUG] bad performance and system stalls when using
dm-crypt
Product: File System
Version: 2.5
Kernel Version: 2.6.35.4
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: ext3
AssignedTo: [email protected]
ReportedBy: [email protected]
Regression: No

Please see
http://thread.gmane.org/gmane.linux.kernel.device-mapper.dm-crypt/4558 for the full mailing list thread that is related to my bug report here :)

Summary:
'Right, I see the issue as the following: requesting a lot of writes and then a number of read operations from different processes leads to a *poor* outcome.
I say this because if I do "dd /dev/zero of=/tmp/DELETEME" after a short time the entire system stalls and it really is *very* difficult to end the dd, which is writing to the disk :)'

---> The first post in the thread I sent to the dm-crypt list :)

I am not sure if this really is a bug or just expected behaviour with ext3 in ordered mode with luks / dm-crypt adding some extra latency
...

----
I am experiencing really bad performance and a fair amount of system stalls using dm-crypt(luks) on debian lenny with with an ext3 ordered mode /

"

Version:        1
Cipher name:    aes
Cipher mode:    cbc-essiv:sha256
Hash spec:      sha1

"
/dev/mapper/foo-root on / type ext3 (rw,relatime,errors=remount-ro) Swap is also within the luks partition.

The kernel version is 2.6.35.4.

A simple test is just to dd if=/dev/zero of=DELETEME for a short time and the system will stall rather a lot - it is not a complete lock up
- just the entire system is unresponsive for large periods at a time (from around 30seconds - to 2 minutes). This may be related to
http://thread.gmane.org/gmane.linux.kernel.mm/51444 .

The system is a 6 core amd phenom with 4gb of ram - the hard drive is a WD 1TB sata 3 drive hooked up to a (sata 3 controller) 00:11.0 SATA controller: ATI Technologies Inc SB700/SB800 SATA Controller [IDE mode] (rev 40)

00:11.0 SATA controller: ATI Technologies Inc SB700/SB800 SATA Controller [IDE mode] (rev 40) (prog-if 01 [AHCI 1.0])
Subsystem: ASUSTeK Computer Inc. Device 8443
Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR+ FastB2B- DisINTx+
Status: Cap+ 66MHz+ UDF- FastB2B- ParErr- DEVSEL=medium

       Latency: 64, Cache Line Size: 64 bytes
       Interrupt: pin A routed to IRQ 42
       Region 0: I/O ports at c000 [size=8]
       Region 1: I/O ports at b000 [size=4]
       Region 2: I/O ports at a000 [size=8]
       Region 3: I/O ports at 9000 [size=4]
       Region 4: I/O ports at 8000 [size=16]
       Region 5: Memory at fe8ffc00 (32-bit, non-prefetchable) [size=1K]
       Capabilities: [50] Message Signalled Interrupts: Mask- 64bit+

Queue=0/2 Enable+
Address: 00000000fee3f00c Data: 4161
Capabilities: [70] SATA HBA <?>
Capabilities: [a4] PCIe advanced features <?> Kernel driver in use: ahci
Kernel modules: ahci

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https://bugzilla.kernel.org/show_bug.cgi?id=18302

--- Comment #1 from david b <[email protected]> 2010-10-24 15:48:56 ---
...
For example:
doing something stupid like this

dd if=/dev/zero of=TEMP count=15553600 & dd if=/dev/zero of=TEMP2 count=15553600 & ls -lahR / &
will --> end up with the following output :/

fsync time: 25.8393
pread time: 0.0010
fsync time: 20.6251
pread time: 0.0007
fsync time: 31.0960
pread time: 5.3767
fsync time: 28.0393
pread time: 16.1137
fsync time: 19.2237
pread time: 12.9312
fsync time: 25.0550
pread time: 6.7220
fsync time: 9.8830
pread time: 0.0009

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Alan <[email protected]> changed:

What |Removed |Added
----------------------------------------------------------------------------

             Status|NEW                         |RESOLVED
                 CC|                            |[email protected]
         Resolution|                            |OBSOLETE

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