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Default nogds to filesystem-aware O_DIRECT - #128
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takeshi-yoshimura merged 1 commit intoOct 8, 2026
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Move the unified copier's filesystem policy into common.is_odirect_enabled and reuse it for nogds. Local and unknown filesystems now use direct I/O by default; known network filesystems and platforms without O_DIRECT retain buffered reads. Benchmark: H100 80GB (one GPU for Granite, four for DeepSeek). Use nogds, queue_size=2, device_memory_budget=-1, enforce-eager, max_model_len=32768, gpu_memory_utilization=0.97/0.8 respectively. NVMe is XFS at /opt/nvme/hf_home; /tmp/tyos/hf_cache is tmpfs. | Model (TP) | Storage | I/O | Cold mean | Warm mean | |--------------|---------|----------|-----------|-----------| | Granite (1) | NVMe | buffered | 11.625691 | 4.198456 | | Granite (1) | NVMe | direct | 4.890897 | 4.810586 | | Granite (1) | tmpfs | buffered | 4.504860 | 4.365668 | | Granite (1) | tmpfs | direct | 4.520546 | 4.242581 | | DeepSeek (4) | NVMe | buffered | 50.294593 | 16.138033 | | DeepSeek (4) | NVMe | direct | 15.921407 | 14.378360 | | DeepSeek (4) | tmpfs | buffered | 11.303327 | 11.471072 | | DeepSeek (4) | tmpfs | direct | 11.514589 | 13.038018 | Cold requests POSIX_FADV_DONTNEED before every load to drop page cache, while warm performs no eviction. I observed similar trends on different models. Some small models showed that bufferred I/O outperformed, but the gain was few seconds. So, in conclusion, I made O_DIRECT as default and let users disable it on some specific cases. Signed-off-by: Takeshi Yoshimura <tyos@jp.ibm.com>
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takeshi-yoshimura
merged commit Oct 8, 2026
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Thanks for landing this, and for the credit. I read the merged change and tried it on a GB10 (ext4/tmpfs/overlayfs) and a ZFS box; notes in #129, plus a small CI one in #130. None of it is urgent. BTW, happy to review before merge whenever that's useful to you. Tag me on anything touching the loaders or the copiers and I'll turn it around quickly. |
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Move the unified copier's filesystem policy into common.is_odirect_enabled and reuse it for nogds. Local and unknown filesystems now use direct I/O by default; known network filesystems and platforms without O_DIRECT retain buffered reads.
Benchmark: H100 80GB (one GPU for Granite, four for DeepSeek). Use nogds, queue_size=2, device_memory_budget=-1, enforce-eager, max_model_len=32768, gpu_memory_utilization=0.97/0.8 respectively. NVMe is XFS at /opt/nvme/hf_home; /tmp/tyos/hf_cache is tmpfs.
Cold requests POSIX_FADV_DONTNEED before every load to drop page cache, while warm performs no eviction.
I observed similar trends on different models. Some small models showed that bufferred I/O outperformed, but the gain was few seconds. So, in conclusion, I made O_DIRECT as default and let users disable it on some specific cases.
Refs #110
Reported-by: @gitbisector