CUDA: scale q8->f16 cache reserve on >=112 GiB cards (fixes session OOM on large models)

ds4_cuda.cu

@@ -514,14 +514,16 @@ static uint64_t cuda_q8_f16_cache_reserve_bytes(uint64_t total_bytes) {
     const uint64_t reserve = cuda_parse_mib_env("DS4_CUDA_Q8_F16_CACHE_RESERVE_MB", &present);
     if (present) return reserve;
 
-    if (total_bytes >= 112ull * 1024ull * 1024ull * 1024ull) {
-        return 512ull * 1048576ull;
-    }
-
     /* The expanded Q8->F16 cache is only an acceleration path.  Keep enough
-     * device memory free for cuBLAS workspaces, transient graph buffers, and
-     * driver bookkeeping instead of letting optional cached weights consume the
-     * last few GiB on 96 GiB cards. */
+     * device memory free for the session/context tensors, cuBLAS workspaces, and
+     * transient graph buffers allocated after model load, instead of letting
+     * optional cached weights consume the last few GiB.
+     *
+     * Do NOT shrink this to a sub-GiB reserve on large (>=112 GiB) cards: a tiny
+     * reserve lets the eager preload fill device memory down to a few hundred MiB
+     * and OOM at session creation on big models (e.g. a ~252 GB GLM-5.2 split
+     * across 2x H200 NVL). Loading an MTP model disables this cache and hides it.
+     * This mirrors PR #446 (same bug on the ROCm runtime, q4q2). */
     const uint64_t min_reserve = 4096ull * 1048576ull;
     const uint64_t pct_reserve = total_bytes / 20u; /* 5% */
     return pct_reserve > min_reserve ? pct_reserve : min_reserve;