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Berlin
Asked: 2016-12-20 15:28:48 +0800 CST

systemd 的 mysqld.service - 无法解析资源值，忽略：40000 - LimitMEMLOCK

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当我为 MYSQL 5.7mysql systemd[1]: [/usr/lib/systemd/system/mysqld.service:39] Failed to parse resource value, ignoring: 40000设置限制时，我在使用 mysql 5.7 的 Centos 7 上遇到了这个错误。LimitMEMLOCK

LimitMEMLOCK=40000
  1. 为什么不能为 设置数字限制LimitMEMLOCK？
  2. 目的是LimitMEMLOCK什么？
  3. 是唯一的灵魂LimitMEMLOCK=infinity吗？

*

#cat /etc/*-release
CentOS Linux release 7.3.1611 (Core)
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

CentOS Linux release 7.3.1611 (Core)
CentOS Linux release 7.3.1611 (Core)

*

service mysqld status
Redirecting to /bin/systemctl status  mysqld.service
● mysqld.service - MySQL Server
   Loaded: loaded (/usr/lib/systemd/system/mysqld.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2016-12-19 23:21:24 UTC; 9s ago
 Main PID: 11170 (mysqld)
   CGroup: /system.slice/mysqld.service
           └─11170 /usr/sbin/mysqld --daemonize --pid-file=/var/run/mysqld/mysqld.pid

mysql systemd[1]: Starting MySQL Server...
mysql mysqld_pre_systemd[11143]: /usr/sbin/restorecon:  Warning no default label for /mnt/data/mysql
mysql systemd[1]: Started MySQL Server.
mysql systemd[1]: [/usr/lib/systemd/system/mysqld.service:39] Failed to parse resource value, ignoring: 40000

在其他 Centos 7 版本 ( CentOS Linux release 7.2.1511 (Core))mysqld.service上使用LimitMEMLOCK=40000.

cat /etc/*-release
CentOS Linux release 7.2.1511 (Core)
NAME="CentOS Linux"
VERSION="7 (Core)"
ID="centos"
ID_LIKE="rhel fedora"
VERSION_ID="7"
PRETTY_NAME="CentOS Linux 7 (Core)"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:centos:centos:7"
HOME_URL="https://www.centos.org/"
BUG_REPORT_URL="https://bugs.centos.org/"

CENTOS_MANTISBT_PROJECT="CentOS-7"
CENTOS_MANTISBT_PROJECT_VERSION="7"
REDHAT_SUPPORT_PRODUCT="centos"
REDHAT_SUPPORT_PRODUCT_VERSION="7"

CentOS Linux release 7.2.1511 (Core)
CentOS Linux release 7.2.1511 (Core)
mysql centos7 systemd

1 个回答

  1. Best Answer

    让我们从systemd 文档开始：

    LimitCPU=, LimitFSIZE=, LimitDATA=, LimitSTACK=, LimitCORE=, LimitRSS=, LimitNOFILE=, LimitAS=, LimitNPROC=, LimitMEMLOCK=, LimitLOCKS=, LimitSIGPENDING=, LimitMSGQUEUE=, LimitNICE=, LimitRTPRIO=, LimitRTTIME=

    对已执行进程的各种资源设置软限制和硬限制。有关资源限制概念的详细信息，请参见setrlimit(2)。

    对于 MEMLOCK，该手册页解释说：

       RLIMIT_MEMLOCK
          The maximum number of bytes of memory that may be locked into
          RAM.  In effect this limit is rounded down to the nearest
          multiple of the system page size.  This limit affects mlock(2)
          and mlockall(2) and the mmap(2) MAP_LOCKED operation.  Since
          Linux 2.6.9 it also affects the shmctl(2) SHM_LOCK operation,
          where it sets a maximum on the total bytes in shared memory
          segments (see shmget(2)) that may be locked by the real user
          ID of the calling process.  The shmctl(2) SHM_LOCK locks are
          accounted for separately from the per-process memory locks
          established by mlock(2), mlockall(2), and mmap(2) MAP_LOCKED;
          a process can lock bytes up to this limit in each of these two
          categories.

          In Linux kernels before 2.6.9, this limit controlled the
          amount of memory that could be locked by a privileged process.
          Since Linux 2.6.9, no limits are placed on the amount of
          memory that a privileged process may lock, and this limit
          instead governs the amount of memory that an unprivileged
          process may lock.

    将内存锁定在 RAM 中可防止内核将其换出。这并不经常这样做，但对于某些性能关键的东西来说它非常有用。数据库是可以充分利用这一点的东西之一。

    将此值设置为 40000 没有任何意义。即使你能做到，它也会削弱数据库并可能导致它崩溃。MySQL 在启用大页面支持时锁定内存，并且文档指出 memlock 必须是无限的（infinity在您的 systemd 单元中）。

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