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System p Performance

2. System p Performance / Improved Out Of The Box Performance. 3/1/2007 6:18 PM. Agenda. VMM Page ReplacementNew defaults reducing the requirement for basic performance tuningVMM File IO Pacing Enabled By DefaultPerformance TunablesTunables are categorized into restricted and non-restricted tuna

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System p Performance

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    1. 7/21/2012 System p Performance / AIX v6.1 Bret Olszewski, breto@us.ibm.com Dirk Michel, dirkm@us.ibm.com

    2. 2 System p Performance / Improved Out Of The Box Performance 3/1/2007 6:18 PM Agenda VMM Page Replacement New defaults reducing the requirement for basic performance tuning VMM File IO Pacing Enabled By Default Performance Tunables Tunables are categorized into restricted and non-restricted tunables AIO Dynamic AIO tuning AIO Fast Path for CIO JFS2 Read only access to files opened with CIO NFS Changes to TCP scaling window, R/W size and number of biod daemons

    3. 3 System p Performance / Improved Out Of The Box Performance 3/1/2007 6:18 PM Memory – AIX Page replacement algorithm Default AIX 5.1, 5.2, 5.3 Tuning gives us: When page replacement begins to run, it selects a page type to steal based on: If the amount of file pages is above maxclient/maxperm, file pages are chosen If the number of file pages is between minperm and maxclient, the type is chosen based on re-paging history If the amount of file pages is below minperm, working storage and file pages are chosen without checking for the re-paging history Re-paging history indicates if individual pages have been written to disk and read back recently Re-paging history adds a degree of uncertainty to the selection process If re-paging history decides to pick working storage pages, system paging may begin This was intended as a “safety” valve, if we are too aggressive in stealing file pages, stop But, sometimes it is triggered by bad luck If re-paging history decides to pick file pages and many file pages are “dirty”, heavy writes to disk can occur This would probably happen eventually due to “sync”, so it is not always as noticeable With AIX 6.1, the basic algorithms remain the same, but the tuning changes

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