Subject: Re: Swap overcommit (was Re: Replacement for grep(1) (part 2))
To: Daniel C. Sobral <>
From: Matthew Dillon <>
List: tech-kern
Date: 07/15/1999 21:57:31
:Technical follow-up:
:Contrary to what I previously said, a number of tests reveal that
:Solaris, indeed, does not overcommit. All non-read only segments,
:and all malloc()ed memory is reserved upon exec() or fork(), and the
:reserved memory is not allowed to exceed the total memory. It makes
:extensive use of read only DATA segments, and has a NON_RESERVE
:mmap() flag.
:Though the foot firmly planted in my mouth ought to prevent me from
:saying anything else, I must say that it does explain a few things
:to me...
:Daniel C. Sobral			(8-DCS)

    Something is weird here.  If the solaris people are using a 
    SWAPSIZE + REALMEM VM model, they have to allow the 
    allocated + reserved space go +REALMEM bytes over available swap 
    space.  If not they are using only a SWAPSIZE VM model.

    Wait - does Solaris normally use swap files or swap partitions?
    Or is it that weird /tmp filesystem stuff?  If it normally uses swap 
    files and allows holes then that explains everything.

					Matthew Dillon