KAIO perf on HPUX

Posted in 1997

Martyn Hodgson — 1 Aug 1997 18:26:51 GMT — source: @@NL@@As part of our upgrade to 7.23 I switched on Kernel Asynchronous@@NL@@IO as this had been recommended to me by an Informix consultant@@NL@@(whose name I don�t remember - shame). I have read the Admin.@@NL@@guide on the subject of KAIO and it seemed a sensible thing to@@NL@@do. I believe I understand what is supposed to happen, i.e. IO is@@NL@@handled by the cpu vp (of which we have one to match the single@@NL@@processor that the instance is configured for) and in doing so@@NL@@avoids the overhead of the context switch to an AIO vp.@@NL@@Unfortunately it had a very detrimental effect on performance. A@@NL@@10 minute query took over half an hour. Clearly there is more to@@NL@@the mechanics of KAIO than I understand.@@NL@@\

Hi, We are running Online version 7.23 on a 2 processor HP machine (HP-UX version 10.20). The Online Instance is configured as if the server has just a single processor, as Informix recommend this is more efficient (I believe that the theory is that a single cpu avoids having to some locking and synchronisation and is therefore faster than a twin processor machine). All of our data is held in raw chunks. The main database is in a single dbspaces of its own (3 raw chunks, no fragmentation). It is a read only database, so the database is Unlogged. \