The existence of OOM is one of the few really stupid things in Linux

The existence of OOM is one of the few really stupid things in Linux

Posted Nov 8, 2009 21:21 UTC (Sun) by epa (subscriber, #39769)
In reply to: The existence of OOM is one of the few really stupid things in Linux by dlang
Parent article: Toward a smarter OOM killer

I don't think it matters much if a few slightly-buggy applications use the wrong variant. If 90% of userspace including the most important programs such as shells passes the right hint to the kernel, the kernel can make better decisions than it does now, and the need for the OOM killer will be reduced. It's a similar situation with raw I/O, for example: a disk-heavy program such as a database server might know that it will scan through a large file just once. Ordinarily this file's contents might clog up the page cache and evict more useful things. To help get more consistent performance, apps can be coded to hint to the kernel that it needn't bother to cache a particular I/O request. The default is still to cache it, and it's not catastrophic if one or two userspace programs haven't been tuned to use the new fancy hinting mechanism.

but forget the fork then exec situation for a moment and consider the real fork situation. for a large app, most of the memory will never get modified by either process, and so even there it will almost never use the 2x memory that has been reserved for it.

Very true, but of course there's no way for the kernel to know this. I expect most apps would prefer the fork to either succeed for sure, or fail at once if not enough memory can be guaranteed. There may be a few where optimistically hoping for the best and perhaps killing a random process later is the ideal behaviour.

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