Hello Simon, Monday, March 13, 2006, 3:40:21 PM, you wrote:
just to check available PHYSICAL memory he answered that he don't know that is physical memory, only virtual memory matters
SM> I think that's a mischaracterisation of what I said. Actually I said SM> that I didn't understand your comment about physical vs. virtual memory, SM> and in fact, looking back at the message, I still don't understand it :) SM> http://www.haskell.org//pipermail/glasgow-haskell-users/2005-April/008373.ht... SM> I think what you're suggesting is that the runtime should detect the SM> amount of physical memory on the system and auto-tune itself to switch SM> to compacting collection when its residency reaches that amount. This SM> is certainly something we could do. Bear in mind that GHC is not SM> necessarily the only process running on the machine, though, and what SM> about running multiple GHCs? i suggest checking of AVAILABLE physical ram, that is perfectly possible in windows SM> Also, you can do this by setting your GHC_RTS environment variable. SM> Suppose you have 1G of physical mem. You want GHC to give up when it SM> reaches 1.5G, and you want to switch to compacting collection when the SM> residency reaches 300M. You could do this: SM> export GHC_RTS='-M1.5G -c20' SM> because 300M is 20% of 1.5G. Perhaps a better interface would be to SM> allow you to specify exactly the residency at which to switch to compaction. you mix up two questions: 1) switching from copying to compacting algorithm 2) return memory to OS after GC the only commonality between them is what we want to do both these things only when we are short on physical memory (1) is possible in GHC. (2) can be implemented, i think. so, the questions is how to trigger each thing. GHC has mechanism to switching GC algorithm although this mechanism is not enough flexible. i personally will prefer to have API that allow to control all GC parameters (although at this moment we also have this api unofficially - we have access to all these variables). so the main question at this time is implementation of returning memory to OS and providing some simple mechanism of enabling this (say, in percents of maximal heap size like this is done "-c"). then someone like me can roll out some API to allow programs better control the entire mechanism -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com