I updated my test case to include the "sync" call inside the "time", because
otherwise recent 64bit installations report wrong results. @v4169sgr, you might
want to test again with 64bit using the updated commands:
1) . /etc/os-release; echo -n "$VERSION, $(uname -r), $(dpkg
--print-architecture), RAM="; awk '/MemTotal:/ { print $2 }' /proc/meminfo
2) mount /dev/sdb2 /mnt && rm -rf /mnt/tmp/lib && mkdir -p /mnt/tmp/lib && sync
&& echo 3 > /proc/sys/vm/drop_caches && chroot /mnt
3) mkdir -p /tmp/lib; cd /tmp/lib; s=/lib; d=1; echo -n "Copying $s to $d: ";
while /usr/bin/time -f %e sh -c "cp -a '$s' '$d'; sync"; do s=$d;
d=$((($d+1)%100)); echo -n "Copying $s to $d: "; done
I managed to find 16 GB RAM and test locally. All 3.x kernels are unaffected,
and all 32 bit 4.x kernels have issues.
14.04, Trusty Tahr, 3.13.0-24-generic, i386, RAM=16076400 [Live CD]
8-13 secs
15.04 (Vivid Vervet), 3.19.0-15-generic, i386, RAM=16083080 [Live CD]
5-7 secs
15.10 (Wily Werewolf), 4.2.0-16-generic, i386, RAM=16082536 [Live CD]
4-350 secs
16.04.2 LTS (Xenial Xerus), 3.19.0-80-generic, i386, RAM=16294832 [HD install]
10-25 secs
16.04.2 LTS (Xenial Xerus), 4.2.0-42-generic, i386, RAM=16294392 [HD install]
14-89 secs
16.04.2 LTS (Xenial Xerus), 4.4.0-79-generic, i386, RAM=16293556 [HD install]
15-605 secs
16.04.2 LTS (Xenial Xerus), 4.8.0-54-generic, i386, RAM=16292708 [HD install]
6-160 secs
16.04.2 LTS (Xenial Xerus), 4.8.0-36-generic, amd64, RAM=16131028 [Live CD]
4-11 secs
** Attachment added: "cp-benchmark"
https://bugs.launchpad.net/ubuntu/+source/linux-hwe/+bug/1698118/+attachment/4898505/+files/cp-benchmark
** Description changed:
This happens on xenial with 4.4 and 4.8 kernels.
- It does not happen on precise with 3.2, nor on trusty with 4.2.
+ It does not happen on precise with 3.2, nor on trusty with 3.19.
The problem is that disk writes start with 200 MB/sec, but after some disk
usage, e.g. after 20-50 GB of writes, they become extremely slow, like 2
MB/sec, and never get fast again.
The difference is really 100 times slower, it's not related to RAM caching,
it makes the system unusable permanately after it appears.
-
- Test case:
+ Test case [edit: see comment #7 below for my updated test case]:
# This copies with 200 MB/sec:
dd if=/dev/zero of=/mnt/test bs=1M count=1000 conv=fdatasync
# This just does some disk writes, because the problem happens gradually
cp -a /mnt/a-20gb-folder /mnt/dest
# Now testing again, it writes with 2 MB/sec:
dd if=/dev/zero of=/mnt/test bs=1M count=1000 conv=fdatasync
After those 3 commands, the system is unusable even if left for hours.
I've only seen it in 2 out of 100 installations so far, so it appears to be
rare...
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.8.0-54-generic 4.8.0-54.57~16.04.1
ProcVersionSignature: Ubuntu 4.8.0-54.57~16.04.1-generic 4.8.17
Uname: Linux 4.8.0-54-generic i686
ApportVersion: 2.20.1-0ubuntu2.6
Architecture: i386
CurrentDesktop: MATE
Date: Thu Jun 15 13:28:43 2017
InstallationDate: Installed on 2017-06-07 (7 days ago)
InstallationMedia: Ubuntu-MATE 16.04.2 LTS "Xenial Xerus" - Release i386
(20170215)
SourcePackage: linux-hwe
UpgradeStatus: No upgrade log present (probably fresh install)
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1698118
Title:
Slow disk writes after some uptime, only on 32bit/16+RAM/4+ kernels
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux-hwe/+bug/1698118/+subscriptions
--
ubuntu-bugs mailing list
[email protected]
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
