What is HugePage size in RHEL for s390x architecture?

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原文链接：https://access.redhat.com/solutions/381883

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#HugePage #HugePages #s390x # #mainframe

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本文详细介绍了Red Hat Enterprise Linux (RHEL) 在s390x架构下HugePage的大小，包括RHEL 5为2MB，RHEL 6和7为1MB，并解释了这些设置在内核源代码中硬编码，无法更改，除非修改并重新编译内核。同时提供了检查HugePage大小的方法。

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SOLUTION 已验证 - 已更新 2018年二月23日03:11 -

English

环境

Red Hat Enterprise Linux 5
Red Hat Enterprise Linux 6
Red Hat Enterprise Linux 7

问题

What is HugePage size in RHEL for s390x architecture and if it can be changed?

决议

HugePage size in Red Hat Enterprise Linux 5 for s390x architecture is 2 megabytes.
HugePage size in Red Hat Enterprise Linux 6 for s390x architecture is 1 megabyte.
HugePage size in Red Hat Enterprise Linux 7 for s390x architecture is 1 megabyte.

There is no possibility to change HugePage size in RHEL with s390x architecture.

根源

HugePage size is hardcoded in the source code of the kernel, so it cannot be changed without modifying the kernel source code and recompilation.

诊断步骤

Check HugePage size in /proc/meminfo file:

Raw

$ cat /proc/meminfo 
...skip...
Hugepagesize:       1024 kB

For s390x architecture, the hugepage size is already defined in the kernel code itself:

RHEL 7:

Raw

arch/s390/include/asm/page.h:

#define HPAGE_SHIFT        20
#define HPAGE_SIZE        (1UL << HPAGE_SHIFT)
#define HPAGE_MASK        (~(HPAGE_SIZE - 1))
#define HUGETLB_PAGE_ORDER        (HPAGE_SHIFT - PAGE_SHIFT)
#define HUGE_MAX_HSTATE                2

RHEL 6:

Raw

arch/s390/include/asm/page.h:

#define HPAGE_SHIFT        20
#define HPAGE_SIZE        (1UL << HPAGE_SHIFT)
#define HPAGE_MASK        (~(HPAGE_SIZE - 1))
#define HUGETLB_PAGE_ORDER        (HPAGE_SHIFT - PAGE_SHIFT)

RHEL 5:

Raw

include/asm-s390/page.h:

#define HPAGE_SHIFT        21
#define HPAGE_SIZE        (1UL << HPAGE_SHIFT)
#define HPAGE_MASK        (~(HPAGE_SIZE - 1))
#define HUGETLB_PAGE_ORDER        (HPAGE_SHIFT - PAGE_SHIFT)