** Package changed: linux-hwe (Ubuntu) => linux (Ubuntu) -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1758621
Title: Ubuntu Xenial HWE Kernel 4.13 Direct Sync Write Performance Regression Status in linux package in Ubuntu: New Bug description: Hi Ubuntu, Just found out today that when using Ubuntu Xenial HWE kernel 4.13 in a VM on top of Proxmox VE 5.1.x, the direct synchronous write performance is 93% slower than on kernel 4.4. Kernel 4.13 direct sync 4KB write could only achieve 303KB/s while kernel 4.4 could achieve 4.5MB/s. The VM is using ext4 filesystem and running on top of ZFS ZVOL on ZFS RAID1 with virtio-scsi, qemu disk cache none, and qemu disk discard enabled. The underlying physical disks are Samsung Enterprise SSD SM863a 480GB series. The reason I need to run kernel 4.13 to mount CephFS Luminous with kernel client. Hopefully CephFS Luminous kernel client will be back ported to kernel 4.4 in the near future. Is this from Ubuntu Xenial kernel 4.13 performance regression or from Proxmox VE 5.1 kernel 4.13 virtio-scsi performance regression? The test results: ## # ubuntu xenial kernel 4.13. the direct synchronous write performance is 93% slower than kernel 4.4 ## root@localhost:~# uname -a Linux localhost 4.13.0-37-generic #42~16.04.1-Ubuntu SMP Wed Mar 7 16:03:28 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux root@localhost:~# dd if=/dev/zero of=/mnt/test/test bs=4K count=256 oflag=direct,sync status=progress; rm /mnt/test/test 1048576 bytes (1.0 MB, 1.0 MiB) copied, 3.46369 s, 303 kB/s ## # ubuntu xenial kernel 4.4. the direct synchronous write performance is 14x faster than kernel 4.13 ## root@localhost:~# uname -a Linux localhost 4.4.0-116-generic #140-Ubuntu SMP Mon Feb 12 21:23:04 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux root@localhost:~# dd if=/dev/zero of=/mnt/test/test bs=4K count=256 oflag=direct,sync status=progress; rm /mnt/test/test 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.231176 s, 4.5 MB/s ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: linux-image-4.13.0-37-generic 4.13.0-37.42~16.04.1 ProcVersionSignature: Ubuntu 4.13.0-37.42~16.04.1-generic 4.13.13 Uname: Linux 4.13.0-37-generic x86_64 ApportVersion: 2.20.1-0ubuntu2.15 Architecture: amd64 Date: Sun Mar 25 13:43:34 2018 InstallationDate: Installed on 2018-03-22 (2 days ago) InstallationMedia: Ubuntu-Server 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228) ProcEnviron: TERM=screen-bce PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash SourcePackage: linux-hwe UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1758621/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
