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About the UBC

About the UBC

何謂UBC呢?謝謝!
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About the UBC

Dear Henry,



The Managing Memory Performance DOC is attached for your reference.



best regards.

About the UBC

The Unified Buffer Cache (UBC) affects disk I/O performance. The UBC is allocated a portion of physical memory to cache most-recently accessed file system data.



可以透過

vm:

ubc_minpercent = 10

ubc_maxpercent = 100

來定義ubc min and max的值

default max is 100%,所以系統允許使用所有的free memory 來當ubc

1)The AdvFS buffer cache is a subset of the UBC.

2)When an AdvFS I/O operation occurs, AdvFS searches the AdvFS buffer cache for the data before querying the UBC for the cache page

3)UFS 的 metadata 放在 wire memory,but file system data 放在UBC

4)AdvFS 的metadata and file data 都是放在UBC

5)Memory Allocation During High File System Activity and No Paging Activity begin allocate UBC

6)Memory Allocation During Low File System Activity and High Paging Activity begin reclaimed UBC