Oracle 5.0, Справочное руководство

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Enabling Large Page Support
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After this, all tables created in the database
mydb
are created in
D:\data\mydb
.
The following limitations apply to the use of
.sym
files for database symbolic linking on Windows:
• The symbolic link is not used if a directory with the same name as the database exists in the MySQL
data directory.
• The
--innodb_file_per_table
[1241] option cannot be used.
• If you run
mysqld
as a service, you cannot use a mapped drive to a remote server as the destination
of the symbolic link. As a workaround, you can use the full path (
\\servername\path\
).
8.9.7. Enabling Large Page Support
Some hardware/operating system architectures support memory pages greater than the default
(usually 4KB). The actual implementation of this support depends on the underlying hardware and
operating system. Applications that perform a lot of memory accesses may obtain performance
improvements by using large pages due to reduced Translation Lookaside Buffer (TLB) misses.
In MySQL, large pages can be used by InnoDB, to allocate memory for its buffer pool and additional
memory pool.
Currently, MySQL supports only the Linux implementation of large page support (which is called
HugeTLB in Linux).
Before large pages can be used on Linux, the kernel must be enabled to support them and it is
necessary to configure the HugeTLB memory pool. For reference, the HugeTBL API is documented in
the
Documentation/vm/hugetlbpage.txt
file of your Linux sources.
The kernel for some recent systems such as Red Hat Enterprise Linux appear to have the large pages
feature enabled by default. To check whether this is true for your kernel, use the following command
and look for output lines containing “huge”:
shell> cat /proc/meminfo | grep -i huge
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 4096 kB
The nonempty command output indicates that large page support is present, but the zero values
indicate that no pages are configured for use.
If your kernel needs to be reconfigured to support large pages, consult the
hugetlbpage.txt
file for
instructions.
Assuming that your Linux kernel has large page support enabled, configure it for use by MySQL using
the following commands. Normally, you put these in an
rc
file or equivalent startup file that is executed
during the system boot sequence, so that the commands execute each time the system starts. The
commands should execute early in the boot sequence, before the MySQL server starts. Be sure to
change the allocation numbers and the group number as appropriate for your system.
# Set the number of pages to be used.
# Each page is normally 2MB, so a value of 20 = 40MB.
# This command actually allocates memory, so this much
# memory must be available.
echo 20 > /proc/sys/vm/nr_hugepages
# Set the group number that is permitted to access this
# memory (102 in this case). The mysql user must be a
# member of this group.
echo 102 > /proc/sys/vm/hugetlb_shm_group
# Increase the amount of shmem permitted per segment
# (12G in this case).
echo 1560281088 > /proc/sys/kernel/shmmax