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Martin Hope
Deltik
Asked: 2016-05-13 16:24:38 +0800 CST
  • 6

我正在将数据迁移到 LUKS 分区中。现在操作系统驱动器正在运行 LUKS，我尝试开始迁移数据驱动器。然后服务器停止响应。

此 LUKS 设备已打开：

cryptsetup luksOpen /dev/sdc data1

这些命令中的任何一个都会扼杀服务器：

pv /dev/zero > /dev/mapper/data1
pv /dev/zero > /dev/sdc

不是立即，而是在几秒钟内，服务器变得异常缓慢。I/O 上的所有内容都被阻塞：

root@node51 [~]# ps aux | awk '{if($8~"D"||$8=="STAT"){print $0}}' 
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root      1197  0.0  0.0      0     0 ?        D    06:39   0:00 [jbd2/dm-1-8]
root      1687  0.1  0.0      0     0 ?        D    11:15   0:12 [kworker/u96:5]
root     13057  2.0  0.0      0     0 ?        D    13:10   0:01 [dmcrypt_write]
root     13644 10.9  0.0   7452   784 pts/1    D+   13:10   0:08 pv /dev/zero
root     14159  0.0  0.0  98256  6836 ?        DNs  13:10   0:00 sshd: root [priv]
root     14772  0.0  0.0  29008    92 ?        D    13:11   0:00 /usr/sbin/CRON -f
root     14773  0.0  0.0  98256  6748 ?        DNs  13:11   0:00 sshd: root [priv]
root     15411  0.0  0.0  98256  6876 ?        DNs  13:11   0:00 sshd: root [priv]
root     16009  0.1  0.0  98256  6840 ?        DNs  13:11   0:00 sshd: root [priv]
root     16632  0.5  0.0  98256  6892 ?        DNs  13:11   0:00 sshd: root [priv]
root     16900  0.0  0.0   5448   356 pts/3    D+   13:11   0:00 awk {if($8~"D"||$8=="STAT"){print $0}}
root     28553  0.6  0.0      0     0 ?        D    12:12   0:21 [txg_sync]

值得注意的是，大约两秒钟，pv报告它正在以超过2GiB/s. 这既是回写缓存，也是填满的脏页（通过监控发现/proc/meminfo）。

之后，pv记录了正常的写入速度，200MiB/s但在回写缓存中仍然领先。2GiB3GiB

由于所有 I/O 阻塞的进行，服务器平均负载跃升至 10.00 以上。

中止写测试需要一段时间，pv因为需要清空回写缓存，但在中止测试后，服务器性能恢复正常。

有趣的是，这些命令不会导致服务器滞后：

# Reads from dm-crypt block device
pv /dev/mapper/data1 > /dev/zero
# Reads from the raw block device
pv /dev/sdc > /dev/zero

# Writes to a control disk of a different model
pv /dev/zero > /dev/sdi
# Reads from a control disk
pv /dev/sdi > /dev/zero

# Writes to a file on a dm-crypt ext4 filesystem on a solid-state drive
pv /dev/zero > /tmp/empty
# Reads from that same solid-state drive
pv /dev/sda > /dev/zero

我有这些问题：

  1. 为什么持续顺序写入此数据磁盘会大大降低服务器速度？
  2. 在写入特定的一个或几个磁盘时，如何避免阻塞其他磁盘？
  3. 为什么这种硬盘会导致性能问题，而其他硬盘却不会？

我有六个相同型号的磁盘（/dev/sdc、/dev/sdd、/dev/sde、/dev/sdf、/dev/sdg和/dev/sdh）要加密，它们将来会有顺序写入工作负载，所以我不希望服务器因这个问题而停滞不前。

附加信息

要闻速览

服务器： 戴尔 PowerEdge T320

核心： Linux node51 4.4.0-22-generic #39-Ubuntu SMP Thu May 5 16:53:32 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

操作系统： Ubuntu Server 16.04 LTS Xenial Xerus 64-bit

有问题的硬盘： 东芝 PH3500U-1I72

我有六个这样的磁盘，它们都被认为是健康的，我测试了其中的两个，并且都经历了服务器范围的 I/O 性能下降。200MiB/s他们几乎在一开始就阅读和写作。

控制（无问题）硬盘： 三星SP1614C

该磁盘的持续写入速度为50MiB/s. 会不会是有问题的磁盘太快了？

磁盘控制器： 戴尔 PERC H310

两个固态驱动器和六个有问题的硬盘驱动器连接到这个控制器，所有这些驱动器都直接作为AHCI传递。控制盘连接到主板内置的 SATA 端口。

I/O 调度程序

root@node51 [/tmp]# tail -n +1 /sys/block/sd*/queue/scheduler 
==> /sys/block/sda/queue/scheduler <==
noop [deadline] cfq 

==> /sys/block/sdb/queue/scheduler <==
noop [deadline] cfq 

==> /sys/block/sdc/queue/scheduler <==
[noop] deadline cfq 

==> /sys/block/sdd/queue/scheduler <==
[noop] deadline cfq 

==> /sys/block/sde/queue/scheduler <==
[noop] deadline cfq 

==> /sys/block/sdf/queue/scheduler <==
[noop] deadline cfq 

==> /sys/block/sdg/queue/scheduler <==
[noop] deadline cfq 

==> /sys/block/sdh/queue/scheduler <==
[noop] deadline cfq 

==> /sys/block/sdi/queue/scheduler <==
noop [deadline] cfq

更改/dev/sdcfrom noopto的调度程序deadline没有明显的区别。将调度程序更改为cfq似乎在一定程度上减少了延迟，但其他磁盘上的 I/O 操作仍然受到影响。

vm.dirty*内核参数

root@node51 [~]# sysctl -a | grep 'vm.dirty'
vm.dirty_background_bytes = 0
vm.dirty_background_ratio = 10
vm.dirty_bytes = 0
vm.dirty_expire_centisecs = 3000
vm.dirty_ratio = 20
vm.dirty_writeback_centisecs = 500
vm.dirtytime_expire_seconds = 43200

检测到并记录到的缓慢示例/var/log/syslog

ZFS 事务组同步：

May 11 19:28:44 node51 kernel: [ 4080.179688] INFO: task txg_sync:3179 blocked for more than 120 seconds.
May 11 19:28:44 node51 kernel: [ 4080.179905]       Tainted: P           O    4.4.0-22-generic #39-Ubuntu
May 11 19:28:44 node51 kernel: [ 4080.180110] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
May 11 19:28:44 node51 kernel: [ 4080.180357] txg_sync        D ffff88060b68baa8     0  3179      2 0x00000000
May 11 19:28:44 node51 kernel: [ 4080.180362]  ffff88060b68baa8 ffff880616a96d00 ffff8806133ea940 ffff880603dc2940
May 11 19:28:44 node51 kernel: [ 4080.180366]  ffff88060b68c000 ffff880616ad6d00 7fffffffffffffff ffff88056cb8c508
May 11 19:28:44 node51 kernel: [ 4080.180368]  0000000000000001 ffff88060b68bac0 ffffffff818211f5 0000000000000000
May 11 19:28:44 node51 kernel: [ 4080.180372] Call Trace:
May 11 19:28:44 node51 kernel: [ 4080.180381]  [<ffffffff818211f5>] schedule+0x35/0x80
May 11 19:28:44 node51 kernel: [ 4080.180385]  [<ffffffff81824315>] schedule_timeout+0x1b5/0x270
May 11 19:28:44 node51 kernel: [ 4080.180390]  [<ffffffff810abe52>] ? default_wake_function+0x12/0x20
May 11 19:28:44 node51 kernel: [ 4080.180395]  [<ffffffff810c33b2>] ? __wake_up_common+0x52/0x90
May 11 19:28:44 node51 kernel: [ 4080.180398]  [<ffffffff81820744>] io_schedule_timeout+0xa4/0x110
May 11 19:28:44 node51 kernel: [ 4080.180412]  [<ffffffffc05afbec>] cv_wait_common+0xbc/0x140 [spl]
May 11 19:28:44 node51 kernel: [ 4080.180416]  [<ffffffff810c3a70>] ? wake_atomic_t_function+0x60/0x60
May 11 19:28:44 node51 kernel: [ 4080.180423]  [<ffffffffc05afcc8>] __cv_wait_io+0x18/0x20 [spl]
May 11 19:28:44 node51 kernel: [ 4080.180487]  [<ffffffffc071320e>] zio_wait+0x10e/0x1f0 [zfs]
May 11 19:28:44 node51 kernel: [ 4080.180528]  [<ffffffffc069ce66>] dsl_pool_sync+0x2c6/0x430 [zfs]
May 11 19:28:44 node51 kernel: [ 4080.180573]  [<ffffffffc06b85b6>] spa_sync+0x366/0xb30 [zfs]
May 11 19:28:44 node51 kernel: [ 4080.180576]  [<ffffffff810abe52>] ? default_wake_function+0x12/0x20
May 11 19:28:44 node51 kernel: [ 4080.180623]  [<ffffffffc06c9a4a>] txg_sync_thread+0x3ba/0x630 [zfs]
May 11 19:28:44 node51 kernel: [ 4080.180669]  [<ffffffffc06c9690>] ? txg_delay+0x180/0x180 [zfs]
May 11 19:28:44 node51 kernel: [ 4080.180676]  [<ffffffffc05aae31>] thread_generic_wrapper+0x71/0x80 [spl]
May 11 19:28:44 node51 kernel: [ 4080.180682]  [<ffffffffc05aadc0>] ? __thread_exit+0x20/0x20 [spl]
May 11 19:28:44 node51 kernel: [ 4080.180686]  [<ffffffff810a0588>] kthread+0xd8/0xf0
May 11 19:28:44 node51 kernel: [ 4080.180688]  [<ffffffff810a04b0>] ? kthread_create_on_node+0x1e0/0x1e0
May 11 19:28:44 node51 kernel: [ 4080.180692]  [<ffffffff8182568f>] ret_from_fork+0x3f/0x70
May 11 19:28:44 node51 kernel: [ 4080.180694]  [<ffffffff810a04b0>] ? kthread_create_on_node+0x1e0/0x1e0

ext4 期刊：

May 11 20:46:46 node51 kernel: [ 6000.186474] INFO: task jbd2/dm-2-8:1148 blocked for more than 120 seconds.
May 11 20:46:46 node51 kernel: [ 6000.193164]       Tainted: P           O    4.4.0-22-generic #39-Ubuntu
May 11 20:46:46 node51 kernel: [ 6000.199950] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
May 11 20:46:46 node51 kernel: [ 6000.208323] jbd2/dm-2-8     D ffff88060a6e7c98     0  1148      2 0x00000000
May 11 20:46:46 node51 kernel: [ 6000.208330]  ffff88060a6e7c98 0000000000000246 ffff8806133eb700 ffff88060b561b80
May 11 20:46:46 node51 kernel: [ 6000.208333]  ffff88060a6e8000 ffff88060aeb68b8 ffff88060a6e7d88 ffff88060a6e7d70
May 11 20:46:46 node51 kernel: [ 6000.208336]  ffff88060b561b80 ffff88060a6e7cb0 ffffffff818211f5 ffff8805fd6af900
May 11 20:46:46 node51 kernel: [ 6000.208339] Call Trace:
May 11 20:46:46 node51 kernel: [ 6000.208355]  [<ffffffff818211f5>] schedule+0x35/0x80
May 11 20:46:46 node51 kernel: [ 6000.208361]  [<ffffffff812ea0e0>] jbd2_journal_commit_transaction+0x240/0x1870
May 11 20:46:46 node51 kernel: [ 6000.208365]  [<ffffffff810b6be1>] ? dequeue_entity+0x431/0xa80
May 11 20:46:46 node51 kernel: [ 6000.208368]  [<ffffffff810b774a>] ? dequeue_task_fair+0x51a/0x8a0
May 11 20:46:46 node51 kernel: [ 6000.208372]  [<ffffffff810c3a70>] ? wake_atomic_t_function+0x60/0x60
May 11 20:46:46 node51 kernel: [ 6000.208378]  [<ffffffff810ec5fe>] ? try_to_del_timer_sync+0x5e/0x90
May 11 20:46:46 node51 kernel: [ 6000.208381]  [<ffffffff812ef32a>] kjournald2+0xca/0x250
May 11 20:46:46 node51 kernel: [ 6000.208384]  [<ffffffff810c3a70>] ? wake_atomic_t_function+0x60/0x60
May 11 20:46:46 node51 kernel: [ 6000.208387]  [<ffffffff812ef260>] ? commit_timeout+0x10/0x10
May 11 20:46:46 node51 kernel: [ 6000.208391]  [<ffffffff810a0588>] kthread+0xd8/0xf0
May 11 20:46:46 node51 kernel: [ 6000.208394]  [<ffffffff810a04b0>] ? kthread_create_on_node+0x1e0/0x1e0
May 11 20:46:46 node51 kernel: [ 6000.208397]  [<ffffffff8182568f>] ret_from_fork+0x3f/0x70
May 11 20:46:46 node51 kernel: [ 6000.208399]  [<ffffffff810a04b0>] ? kthread_create_on_node+0x1e0/0x1e0
May 11 20:46:46 node51 kernel: [ 6292.776357] perf interrupt took too long (2539 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
performance hard-drive linux io
Martin Hope
Deltik
Asked: 2015-06-04 10:34:03 +0800 CST
  • 1

我做了一些愚蠢的事情：我启用xend并libxl使用xend.

现在，libxl即使我摆脱了所有xend实例并停止了，也不会启动任何实例xend：

root@xen1 [~]# virsh start xen-pv-yolo
error: Failed to start domain xen-pv-yolo
error: internal error: libxenlight failed to create new domain 'xen-pv-yolo'

从日志文件/var/log/libvirt/libxl/xen-pv-yolo.log：

libxl: debug: libxl_create.c:1342:do_domain_create: ao 0x7fea1c0075c0: create: how=(nil) callback=(nil) poller=0x7fea1c001400
libxl: error: libxl_create.c:600:libxl__domain_make: cannot change hotplug execution option once set, please shutdown all guests before changing it
libxl: error: libxl_create.c:743:initiate_domain_create: cannot make domain: -3
libxl: debug: libxl_event.c:1591:libxl__ao_complete: ao 0x7fea1c0075c0: complete, rc=-3
libxl: debug: libxl_create.c:1356:do_domain_create: ao 0x7fea1c0075c0: inprogress: poller=0x7fea1c001400, flags=ic
libxl: debug: libxl_event.c:1563:libxl__ao__destroy: ao 0x7fea1c0075c0: destroy

我有一些现有的libxl实例正在运行，如果为了重新确立 的主导地位而关闭它们会带来不便libxl。

启用和禁用后如何libxl重新启动实例xend？

众所周知，重新启动可以解决此问题，但我更愿意避免重新启动。

linux