4 ms·

I'm not quite sure mmap is such a good idea if you're trying to have more low-level control over performance. Weird Carmack advocating this, because you can't r

by angch 10y ago

I'm not quite sure mmap is such a good idea if you're trying to have more low-level control over performance. Weird Carmack advocating this, because you can't really guarantee the latency of grabbing any resource if you incur a fault and need to grab it from disk. See also the comments from https://news.ycombinator.com/item?id=8704911 https://news.ycombinator.com/item?id=8704911

robert_tweed 10y ago
Just guessing, but from my reading it sounds like the aim is to maintain generally good frame rates and not worry too much about dropped frames due to page faults, since those will be rare. Presumably the idea is to rely on ATW so that when frames do get dropped, it's imperceptible.
HelloNurse 10y ago
He notes that reasonable hardware should have the performance margin to load a reasonable number of pages from a SSD without dropping a frame, which seems a very good plan. Looking forward to actual tests, of course. Considering that prefetching schemes allow the programmer to spread asset loading evenly over many frames, and cheap rendering approximations can be used in troublesome frames, there should also be enough low-level control.
- lazyjones 10y ago
  > reasonable hardware should have the performance margin to load a reasonable number of pages from a SSD without dropping a frame My disks are usually encrypted though and sometimes I can choose faster or slower encryption methods (thus affecting throughput when loading). I don't see how this can work reliably without forcing the user to reserve specific disk areas just for GPU assets.
  - wtallis 10y ago
    Why aren't you using a self-encrypting SSD?
CyberDildonics 10y ago
It doesn't mean that everything has to be done like this, only that it would be an available feature. Even then you could touch memory to make sure it is available.

4 ms·

I'm not quite sure mmap is such a good idea if you're trying to have more low-level control over performance. Weird Carmack advocating this, because you can't r

by angch 10y ago

robert_tweed 10y ago
Just guessing, but from my reading it sounds like the aim is to maintain generally good frame rates and not worry too much about dropped frames due to page faults, since those will be rare. Presumably the idea is to rely on ATW so that when frames do get dropped, it's imperceptible.
HelloNurse 10y ago
He notes that reasonable hardware should have the performance margin to load a reasonable number of pages from a SSD without dropping a frame, which seems a very good plan. Looking forward to actual tests, of course. Considering that prefetching schemes allow the programmer to spread asset loading evenly over many frames, and cheap rendering approximations can be used in troublesome frames, there should also be enough low-level control.
- lazyjones 10y ago
  > reasonable hardware should have the performance margin to load a reasonable number of pages from a SSD without dropping a frame My disks are usually encrypted though and sometimes I can choose faster or slower encryption methods (thus affecting throughput when loading). I don't see how this can work reliably without forcing the user to reserve specific disk areas just for GPU assets.
  - wtallis 10y ago
    Why aren't you using a self-encrypting SSD?
CyberDildonics 10y ago
It doesn't mean that everything has to be done like this, only that it would be an available feature. Even then you could touch memory to make sure it is available.