Hi, I'm seeing random temporary freezes (up to 2 seconds) under memory pressure. Before I describe the exact circumstances, I'd like to say that this is a serious issue affecting playability of certain AAA Linux games. In order to reproduce this, an application should: - allocate a few very large buffers (256-512 MB per buffer) - allocate more memory than there is available VRAM. The issue also occurs (but at a lower frequency) if the app needs only 80% of VRAM. Example: ttm_bo_validate needs to migrate a 512 MB buffer. The total size of moved memory for that call can be as high as 1.5 GB. This is always followed by a big temporary drop in VRAM usage. The game I'm testing needs 3.4 GB of VRAM. Setups: Tonga - 2 GB: It's nearly unplayable, because freezes occur too often. Fiji - 4 GB: There is one freeze at the beginning (which is annoying too), after that it's smooth. So even 4 GB is not enough. Workarounds: - Split buffers into smaller pieces in the kernel. It's not necessary to manage memory at page granularity (64KB). Splitting buffers into 16MB-large pieces might not be optimal but it would be a significant improvement. - Or do the same in Mesa. This would prevent inter-process and inter-API buffer sharing for split buffers (DRI, OpenCL), but we would at least verify how much the situation improves. Other issues sharing the same cause: - Allocations requesting 1/3 or more VRAM have a high chance of failing. It's generally not possible to allocate 1/2 or more VRAM as one buffer. Comments welcome, Marek
