[TCLCORE] Re: Memory Allocators (wasHintermayer's string allocation patch)

[Jim I. <ji...@ap...>]

Brent,

Yeah...  It has a dynamic swap file, rather than a separate swap partition.  So the swap size is bounded above by the size of your disk not the size of the swap partition.  It is bounded below by some default "smallest swap size".  I couldn't find where this is set, but somewhere in the /etc forest or in the NetInfo database, one or the other. 

It also seems (I haven't looked at the code, this is just from watching as I filled up my disk) that it will stop to compress unused swap as it goes along.  It is a little too agressive, I think, so that when I had filled up my entire disk, and then tried to launch gdb on gdb, it actually tried to do it, but went into a seemingly endless cycle of crunching the disk.  However, I could reboot the machine and it came up with no disk errors, so the failure mode is not that bad, and the upside is pretty nice...  

Appropriate for a desktop system, but maybe not for a server, where anything that might compromise the system's running should be killed immediately.  You can of course do all the classic Unix admin stuff, and limit process sizes, # of processes, etc for any/all users, if you want to make a MacOS X system secure from external attacks or malicious users.  Needless to say, I don't do this for myself.  If I hang the machine in this way, it is usually my fault (and I haven't been able to for a while without trying pretty hard - which is nice).

Jim  

On Wednesday, August 30, 2000, at 10:06 PM, Brent Welch wrote:

> Apparently MacOS is more advanced than UNIX in this area.  In UNIX you have 
> to be able to allocate the swap space to cover the virtual memory.  So, in practice, 
> if you have 300 Meg of swap space, 192 Meg of real memory, and a 160 Meg string, 
> you cannot append one byte to it in Tcl. 
>  
>  

--
Jim Ingham                                   ji...@ap...
Developer Tools - gdb
Apple Computer

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