Package: mount Version: 2.17.2-3.3 Severity: important Hello all,
I'm currently playing with xen and some intensive parallel I/O requests on disks. I've remark some performance issues on XEN bring by losetup which drop the NCQ/TCQ/Queuing functionnality (which is really useful in parallel random access disk) I'm using this C program to measure the performance impact : http://box.houkouonchi.jp/seeker_baryluk.c (found on this website : http://www.linuxinsight.com/how_fast_is_your_disk.html ) Please find some benchmark : Performance of /dev/dm-2 (lvm) with 1 thread : 210 seeks/secs r...@srv-xen1:~# ./seeker_baryluk /dev/dm-2 1 [1 threads] Results: 210 seeks/second, 4.755 ms random access time (33493245 < offsets < 60740308117) Performance of /dev/dm-2 with 32 threads : 699 seeks/secs (at least 3x times better) r...@srv-xen1:~# ./seeker_baryluk /dev/dm-2 32 [32 threads] Results: 699 seeks/second, 1.430 ms random access time (8670248 < offsets < 60740120558) We are mapping /dev/dm-2 on /dev/loop0 (Yes, just a mapping of LVM drive without any FS interaction) r...@srv-xen1:~# losetup /dev/loop0 /dev/dm-2 Performance of /dev/loop0 with 1 thread : exactly the same performance as direct random seek (good point here) r...@srv-xen1:~# ./seeker_baryluk /dev/loop0 1 [1 threads] Results: 210 seeks/second, 4.757 ms random access time (4255332 < offsets < 60739140845) Performance of /dev/loop0 with 32 threads : 211 seeks/mins <- Here we have "catastrophic" performance issues because we completly lost performance bring by NCQ/TCQ/Queuing !! r...@srv-xen1:~# ./seeker_baryluk /dev/loop0 32 [32 threads] Results: 211 seeks/second, 4.735 ms random access time (14948337 < offsets < 60737675221) Best regards, Grégory -- System Information: Debian Release: squeeze/sid APT prefers testing APT policy: (500, 'testing') Architecture: amd64 (x86_64) Kernel: Linux 2.6.32-5-xen-amd64 (SMP w/2 CPU cores) Locale: LANG=fr_LU.UTF-8, LC_CTYPE=fr_LU.UTF-8 (charmap=UTF-8) Shell: /bin/sh linked to /bin/dash Versions of packages mount depends on: ii libblkid1 2.17.2-3.3 block device id library ii libc6 2.11.2-7 Embedded GNU C Library: Shared lib ii libselinux1 2.0.96-1 SELinux runtime shared libraries ii libsepol1 2.0.41-1 SELinux library for manipulating b ii libuuid1 2.17.2-3.3 Universally Unique ID library mount recommends no packages. Versions of packages mount suggests: ii nfs-common 1:1.2.2-4 NFS support files common to client -- no debconf information -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
