URL: https://docs.oracle.com/cd/E11882_01/server.112/e10839/appi_vlm.htm#UNXAR393
Enabling HugePages makes it possible for the operating system to support memory pages greater than the default (usually 4KB).
Using very large page sizes can improve system performance by reducing the amount of system resources required to access page table entries.
HugePages is useful for both 32-bit and 64-bit configurations.
HugePage sizes vary from 2MB to 256MB, depending on the kernel version and the hardware architecture.
For Oracle Databases, using HugePages reduces the operating system maintenance of page states,
and increases Translation Lookaside Buffer (TLB) hit ratio.
The following are the advantages of using HugePages:
Increased performance through increased TLB hits.
Pages are locked in memory and are never swapped out which guarantees that shared memory like SGA remains in RAM.
Contiguous pages are preallocated and cannot be used for anything else but for System V shared memory (for example, SGA)
Less bookkeeping work for the kernel for that part of virtual memory due to larger page sizes
Ex:-
$grep -i huge /proc/meminfo
HugePages_Total: 5120 ===> No Units.
HugePages_Free: 5120
HugePages_Rsvd: 0
Hugepagesize: 2048 kB
where:
HugePages_Total = is the size of the pool of hugepages.
HugePages_Free = is the number of hugepages in the pool that are not yet allocated.
HugePages_Rsvd = is short for "reserved," and is the number of hugepages
for which a commitment to allocate from the pool has been made, but no
So here total huge page configured is , 5120 * 2048(kb) = 10240 MB ~ 10 GB
Always Huge page should be equal or less than available RAM.
Enabling HugePages makes it possible for the operating system to support memory pages greater than the default (usually 4KB).
Using very large page sizes can improve system performance by reducing the amount of system resources required to access page table entries.
HugePages is useful for both 32-bit and 64-bit configurations.
HugePage sizes vary from 2MB to 256MB, depending on the kernel version and the hardware architecture.
For Oracle Databases, using HugePages reduces the operating system maintenance of page states,
and increases Translation Lookaside Buffer (TLB) hit ratio.
The following are the advantages of using HugePages:
Increased performance through increased TLB hits.
Pages are locked in memory and are never swapped out which guarantees that shared memory like SGA remains in RAM.
Contiguous pages are preallocated and cannot be used for anything else but for System V shared memory (for example, SGA)
Less bookkeeping work for the kernel for that part of virtual memory due to larger page sizes
Ex:-
$grep -i huge /proc/meminfo
HugePages_Total: 5120 ===> No Units.
HugePages_Free: 5120
HugePages_Rsvd: 0
Hugepagesize: 2048 kB
where:
HugePages_Total = is the size of the pool of hugepages.
HugePages_Free = is the number of hugepages in the pool that are not yet allocated.
HugePages_Rsvd = is short for "reserved," and is the number of hugepages
for which a commitment to allocate from the pool has been made, but no
So here total huge page configured is , 5120 * 2048(kb) = 10240 MB ~ 10 GB
Always Huge page should be equal or less than available RAM.
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