Script used to tune bcache devices
** Attachment added: "tune-bcache"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1806015/+attachment/5217652/+files/tune-bcache
** Description changed:
Whilst diagnosing a disk performance issue on our QA cloud, I did some
performance testing of bcache fronted spindles to compare xenial (4.4
kernel) and bionic (4.14 kernel) installs on the same hardware.
A vanilla install (with no tuning of bcache configuration) resulted in
the following performance metrics (using the sysbench fileio rndrw
benchmark):
Xenial
4 threads:
- 45.77 MiB/sec read
- 30.52 MiB/sec write
+ 45.77 MiB/sec read
+ 30.52 MiB/sec write
48 threads (matching core count):
- 138.72 MiB/sec read
- 92.52 MiB/sec write
+ 138.72 MiB/sec read
+ 92.52 MiB/sec write
Bionic
4 threads:
- 29.51 MiB/sec
- 19.67 MiB/sec
+ 29.51 MiB/sec
+ 19.67 MiB/sec
48 threads (matching core count):
- 41.35 MiB/sec
- 27.59 MiB/sec
+ 41.35 MiB/sec
+ 27.59 MiB/sec
-
- After tuning (disabling the congested_{read|write}_threshold_us and disabling
sequential cutoff)
+ After tuning (disabling the congested_{read|write}_threshold_us and
+ disabling sequential cutoff)
Xenial
48 threads (matching core count):
- 153.60 MiB/sec
- 102.40 MiB/sec
+ 153.60 MiB/sec
+ 102.40 MiB/sec
Bionic
48 threads (matching core count):
- 161.49 MiB/sec
- 107.67 MiB/sec
+ 161.49 MiB/sec
+ 107.67 MiB/sec
- suggestion is this might be something todo with the move from deadline
- to cfq as the default IO scheduler between 4.4 and 4.13 but as you can
- see the baseline vanilla performance is significantly slower.
+ suggestion is this might be something todo with the move from deadline to cfq
as the default IO scheduler between 4.4 and 4.13 but as you can see
+ the baseline vanilla performance is significantly slower.
+
+ As a further reference point, the IO performance on the NVMe device
+ supporting the bcache device is:
+
+ 4 threads:
+ 554.56 MiB/sec read
+ 369.71 MiB/sec write
+
ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-generic 4.15.0.39.41
ProcVersionSignature: Ubuntu 4.15.0-39.42-generic 4.15.18
Uname: Linux 4.15.0-39-generic x86_64
AlsaDevices:
- total 0
- crw-rw---- 1 root audio 116, 1 Nov 29 11:38 seq
- crw-rw---- 1 root audio 116, 33 Nov 29 11:38 timer
+ total 0
+ crw-rw---- 1 root audio 116, 1 Nov 29 11:38 seq
+ crw-rw---- 1 root audio 116, 33 Nov 29 11:38 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay': 'aplay'
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord':
'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq',
'/dev/snd/timer'] failed with exit code 1:
Date: Fri Nov 30 10:11:54 2018
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig': 'iwconfig'
Lsusb:
- Bus 002 Device 002: ID 8087:8002 Intel Corp.
- Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
- Bus 001 Device 003: ID 413c:a001 Dell Computer Corp. Hub
- Bus 001 Device 002: ID 8087:800a Intel Corp.
- Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
+ Bus 002 Device 002: ID 8087:8002 Intel Corp.
+ Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
+ Bus 001 Device 003: ID 413c:a001 Dell Computer Corp. Hub
+ Bus 001 Device 002: ID 8087:800a Intel Corp.
+ Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Dell Inc. PowerEdge R630
PciMultimedia:
-
+
ProcEnviron:
- TERM=xterm-256color
- PATH=(custom, no user)
- XDG_RUNTIME_DIR=<set>
- LANG=C.UTF-8
- SHELL=/bin/bash
+ TERM=xterm-256color
+ PATH=(custom, no user)
+ XDG_RUNTIME_DIR=<set>
+ LANG=C.UTF-8
+ SHELL=/bin/bash
ProcFB: 0 mgadrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-39-generic
root=UUID=a361a524-47eb-46c3-8a04-e5eaa65188c9 ro hugepages=103117 iommu=pt
intel_iommu=on
RelatedPackageVersions:
- linux-restricted-modules-4.15.0-39-generic N/A
- linux-backports-modules-4.15.0-39-generic N/A
- linux-firmware 1.173.2
+ linux-restricted-modules-4.15.0-39-generic N/A
+ linux-backports-modules-4.15.0-39-generic N/A
+ linux-firmware 1.173.2
RfKill: Error: [Errno 2] No such file or directory: 'rfkill': 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/08/2016
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 2.3.4
dmi.board.name: 02C2CP
dmi.board.vendor: Dell Inc.
dmi.board.version: A03
dmi.chassis.type: 23
dmi.chassis.vendor: Dell Inc.
dmi.modalias:
dmi:bvnDellInc.:bvr2.3.4:bd11/08/2016:svnDellInc.:pnPowerEdgeR630:pvr:rvnDellInc.:rn02C2CP:rvrA03:cvnDellInc.:ct23:cvr:
dmi.product.name: PowerEdge R630
dmi.sys.vendor: Dell Inc.
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https://bugs.launchpad.net/bugs/1806015
Title:
bcache: performance regression without tuning under bionic
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