Messages in this thread | | | Date | Fri, 24 Mar 2000 23:27:51 -0700 | From | Richard Gooch <> | Subject | Re: Avoiding OOM on overcommit...? |
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Andreas Dilger writes: > Olaf Weber writes: > > In a similar vein, if a process dies due to SIGXCPU or SIGXFSZ that > > you know it dies because it ran into a cpu or file limit. Yes, I > > would like to have some OS support from an overcommitting OS, so that > > if it decides to kill a process of mine because it ran out memory I > > get SIGXMEM instead of SIGBUS. > > If you look at the AIX documentation, they have a signal like this. The > following is quoted from the following URL, and I urge people posting to > this OOM thread to read this document to get a better understanding of > what a system with (optional) no-overcommit behaves like. > > http://www.rs6000.ibm.com/doc_link/en_US/a_doc_lib/aixbman/admnconc/pag_space_under.htm > > "The system monitors the number of free paging space blocks and > detects when a paging-space shortage exists. When the number of free > paging-space blocks falls below a threshold known as the paging-space > warning level, the system informs all processes (except kprocs) > of this condition by sending the SIGDANGER signal. If the shortage > continues and falls below a second threshold known as the paging-space > kill level, the system sends the SIGKILL signal to processes that are > the major users of paging space and that do not have a signal handler > for the SIGDANGER signal (the default action for the SIGDANGER signal > is to ignore the signal). The system continues sending SIGKILL signals > until the number of free paging-space blocks is above the paging-space > kill level." > > Those advocates of "no OOM possible" implementations should read the part: > > "The AIXwindows server currently requires more than 250MB of paging space > when the application runs in early allocation mode." > > It is interesting to note that memory overcommit has recently been ADDED > to AIX, arguably one of the most popular MISSION CRITICAL BUSINESS Unixes.
??? I recall seeing SIGDANGER and SIGKILL on low memory back in 1991 when we using some AIX machines. I wouldn't call that recent.
Regards,
Richard.... Permanent: rgooch@atnf.csiro.au Current: rgooch@ras.ucalgary.ca
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