Le mercredi, 6 ao{ 2003, ` 16:12 Europe/Paris, Jim Magee a icrit : On Wednesday, August 6, 2003, at 7:04 AM, Jonas Maebe wrote: On woensdag, aug 6, 2003, at 12:50 Europe/Brussels, Stiphane Sudre wrote: } else if (retval != KERN_RESOURCE_SHORTAGE) { /* would like to cause a zone_gc() */ (1) panic("zalloc"); } ---- Q: Instead of panicing at (1), couldn't it just be possible to return NULL? KERN_RESOURCE_SHORTAGE is described as: /* A system resource could not be allocated to fulfill * this request. This failure may not be permanent. */ The issue is that once you "Kernel Panic"ed, it's 'permanent' till the next reboot. Note that it panics if retval is *different* from KERN_RESOURCE_SHORTAGE". So in case of KERN_RESOURCE_SHORTAGE, whatever comes below will be executed. Correct. The issue is that most kernel code expects zalloc() to wait until memory is available. They only expect a NULL return in the cases that they specified that they are unwilling to block for memory allocation. However, one of the "different from KERN_RESOURCE_SHORTAGE" errors actually occurs as a result of the kernel's virtual address space being exhausted (rather than just being short of free page frames at the moment). It is extremely unlikely that this "exhausted virtual memory space" situation will rectify itself by having the current thread wait. So we panic. This is somewhat analogous to malloc(). It will normally wait for memory to become available (including waiting for the kernel to select and page out other application pages, etc...). But if the virtual address space of your application is completely exhausted, there's not much that can be done. The good news is that the Darwin 10.7 (Panther) PowerPC[1] kernel supports a significantly larger kernel virtual address space. So the odds of hitting that panic go WAY down (most existing machines can't handle enough physical memory to trigger it). There are also additional hand and soft resource limits added to keep applications from inducing run-away kernel allocations. Side question: Is there a way or a tool to monitor kernel memory (free) space? _______________________________________________ darwin-kernel mailing list | darwin-kernel@lists.apple.com Help/Unsubscribe/Archives: http://www.lists.apple.com/mailman/listinfo/darwin-kernel Do not post admin requests to the list. They will be ignored.