andrew@bhpese.bhpese.oz (Andrew Steele) (12/02/88)
This is a quick question.
If in a program you have the following statement :
ptr = AllocMem( 100L , MEMF_FAST );
how will the Amiga handle the case when the is no fast ram left ?
I would think that a lack of fast ram would cause chip ram to be allocated
but I can't find anywhere that explicitly says that this is the case.
_____
Andrew Steele /_ _\ Spengat Technologies,
_ | | _ c/o Electrical Computer Services,
ACSnet : andrew@bhpese.oz /__| |__\ BHP Rod & Bar Products Division,
INTERNET: andrew@bhpese.oz.au Newcastle, NSW, Australia.
UUCP : ...!{uunet,mcvax}!munnari!bhpese.oz!andrewraddison@castor.usc.edu (Richard Addison) (12/03/88)
In <155@bhpese.bhpese.oz> andrew@bhpese.bhpese.oz (Andrew Steele) writes: >This is a quick question. >If in a program you have the following statement : > > ptr = AllocMem( 100L , MEMF_FAST ); > >how will the Amiga handle the case when the is no fast ram left ? > >I would think that a lack of fast ram would cause chip ram to be allocated >but I can't find anywhere that explicitly says that this is the case. If you ask for MEMF_FAST, you will only get memory that is identified as FAST; if you ask for MEMF_CHIP, you will only get CHIP memory; if you ask for MEMF_PUBLIC, you will get PUBLIC memory. Note that these are not strictly mutually exclusive. Granted, in the current system design, CHIP and FAST are distinct, but AllocMem would operate happily on a MemHeader that is marked both CHIP and FAST. In fact, all memory on the Amiga is now marked PUBLIC as well as either CHIP or FAST. (Aside: I sure hope anyone who wants their software to survive any upgrade to an MMU version of Exec pays strict attention to allocating shared data objects in PUBLIC memory!) Now back to what you really want: Try: if (!(ptr = AllocMem(100L,MEMF_FAST))) ptr = AllocMem(100L,0L); So, if there isn't a block of FAST memory that satisfies your request, you ask for any old block of memory! Be aware that AllocMem will try to purge Libraries and Devices that are not currently open before it returns a NULL pointer. Richard Addison (Remember that episode of Gilligan's Island where they almost got of the island?)
dillon@POSTGRES.BERKELEY.EDU (Matt Dillon) (12/05/88)
:andrew@bhpese.oz.au (Andrew Steele): :This is a quick question. :If in a program you have the following statement : : : ptr = AllocMem( 100L , MEMF_FAST ); : :how will the Amiga handle the case when the is no fast ram left ? If you specify MEMF_FAST, and not enough fast memory exists, NULL will be returned. Normally, I do this: ptr = AllocMem( <blah>, MEMF_PUBLIC); OR ptr = AllocMem( <blah>, 0); OR Here, since you are not specifying any particular type of memory, the system first checks FAST memory, and if not enough exists it then tries to allocate from CHIP memory. It doesn't really matter whether MEMF_PUBLIC is specified or not (it is unclear when one should specify it and when one should not, and the current OS does not care). >I would think that a lack of fast ram would cause chip ram to be allocated >but I can't find anywhere that explicitly says that this is the case. Only if you don't specify a specific type of memory as I did in my example. . o . o . // O -Matt\|/ * "The trajectory failed due to an ill-considered rounding of the floating point quantity by the compiler"
phil@titan.rice.edu (William LeFebvre) (12/10/88)
In article <2077@nunki.usc.edu> raddison@castor.usc.edu (Richard Addison) writes: >If you ask for MEMF_FAST, you will only get memory that is identified as >FAST; if you ask for MEMF_CHIP, you will only get CHIP memory; if you ask >for MEMF_PUBLIC, you will get PUBLIC memory. >... >(Aside: I sure hope anyone who wants their software to survive any >upgrade to an MMU version of Exec pays strict attention to allocating >shared data objects in PUBLIC memory!) The documentation is not particularly clear when something should be public and when it should not be. For example, does the string pointed to by an IntuiText structure need to be public? My intuition (no pun intended) says "yes". It would also be handy if it was easy to pre-declare hunks to be, say, both chip and public. "atom" sure won't let you do it! In fact, it's not even clear to me if atom's idea of "public" is the same as MEMF_PUBLIC. The documentation implies (at least to me) that using atom to change something to "p" just means that it can come out of either chip or fast. That's not quite the same thing. I'd like to put all my Intuition structures (new window and the gadgets especially) in the same hunk and just delcare that hunk to be public: I don't want to have to AllocMem all those suckers. But, at least in A68K, I'm not sure that I can request that a given hunk be public. William LeFebvre Department of Computer Science Rice University <phil@Rice.edu>