llama.cpp

58325573 - llama: narrow the random-access mmap advice to the gather table

llama: narrow the random-access mmap advice to the gather table The advice was applied per mapping: every mapping the model kept got POSIX_MADV_RANDOM plus a whole-file POSIX_FADV_RANDOM, and the eager pull-in was skipped for every file. On qwen4exp that also hit token_embd.weight, which sits 0.33 GiB past the PLE table in the same shard and is read densely, not by sparse gathers. Measured over -c 512 --chunks 60 on IQ1_S it fell to 8.45% resident, against 100% with the feature off. A model now nominates its gather tables (qwen4exp: per_layer_tok_embd) and only those byte ranges are advised. The range is rounded out to whole pages, which on this model takes in 832 bytes before and 192 after. token_embd goes back to 86.55% resident and the PLE table still drops to 4.44%; smaps shows one VM_RAND_READ VMA of exactly the table instead of one over all 27.16 GiB that stays mapped. posix_fadvise is dropped from the narrowed path. POSIX_FADV_RANDOM ignores its offset and length and marks the whole open file, and the FMODE_RANDOM it sets is only read by page_cache_sync_ra() on the read() path, which a fault on a MADV_RANDOM vma never reaches. POSIX_FADV_ DONTNEED does take a range, so the drop mode keeps it. The eager pull-in is now skipped only for the files holding a nominated table, and re-issued as WILLNEED over the rest of such a file, so other shards load exactly as before. prefetch_rows() keys off the tensor being nominated rather than off a mapping-level flag, so the batched readahead lands only where the advice did. -c 512 --chunks 60, cold, IQ1_S, mean of 3, total wall: default 32.50 s whole mapping 30.05 s narrowed 30.35 s PPL 4.2061 in all three. IQ1_S KLD is bit-identical with the feature on and off, including Mean KLD 0.396070 +/- 0.001931 and Same top p 77.325%. tg128 73.65 +/- 0.33 narrowed against 73.49 +/- 0.34 whole. Assisted-by: Claude