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* DSV4 checkpoints WIP
* DSV4 checkpoints: fix per-sequence state save/restore writing all streams
Critical bug: llama_state_seq_get_data() and llama_state_seq_set_data()
were serializing/deserializing ALL DSV4 compressed cache streams instead
of only the stream for the target sequence. This corrupted other active
sequences' compressed indexer state during checkpoint restore.
Fix:
- Add dsv4_stream_offset_size() helper to compute per-stream byte
offset and size for any DSV4 cache tensor (CSA K, LID K, HCA K,
and all state tensors)
- write_kv_cache_data: emit dsv4_single_stream flag + stream_idx
so per-sequence saves only write that stream's portion
- write_dsv4_cache: accept stream_idx parameter (-1 = full tensor,
>= 0 = single stream at computed offset)
- read_kv_cache_data: read the new format, validate consistency
(per-stream data needs dest seq_id, full data needs seq_id=-1),
and restore only the destination stream's bytes into the correct
tensor offset
Format change (WIP, backward compat not required):
[has_dsv4_cache] [n_layer] [single_stream] [stream_idx] [n_stream]
[per-layer: layer_type + stream tensor data]
* DSV4 checkpoints: fix checkpoint search using pos_max instead of pos_min
Bug: checkpoint search condition cur.pos_min < n_past || cur.pos_min == 0
always matched all DSV4 checkpoints because they all have pos_min=0 (the KV
cache starts at 0 and never evicts). The reverse-iterator always picked the
NEWEST checkpoint regardless of how far past the intended rewind/divergence
point it extended, causing n_past to be set to the checkpoint's pos_max
(e.g. 9500) instead of the rewind point (e.g. 5000). This made the system
skip reprocessing tokens between the rewind point and the checkpoint's
pos_max.
Fix in both batch_pending_prompt and apply_checkpoint:
- Condition changed to cur.pos_max < n_past — only checkpoints that end
BEFORE the divergence/rewind point are eligible
- Post-restore n_past uses it->pos_max directly instead of the incorrect
max(pos_min + 1, pos_max) which always returned pos_max for DSV4 anyway
Now when rewinding to position 5000 with checkpoints at pos_max=8000+:
no checkpoint matches, falls through to full reprocessing (correct).
When rewinding to position 8000 with a checkpoint at pos_max=7500: only
500 tokens need reprocessing (optimal).
* DSV4 checkpoints: throttle creation via interval gating on all paths
When ctx_checkpoints_interval > 0, DSV4 checkpoints (~145 MiB) were still
created at every transition point (PP done, TG start, release) because
direct create_checkpoint() calls bypassed the interval gate.
Fix:
- Modified create_checkpoint_at_interval() to handle interval <= 0 as
'always create' (preserving recurrent model behavior for small state)
- Replaced all 4 external direct create_checkpoint() calls with
create_checkpoint_at_interval() so the interval gate is respected
- Unified the prompt-loading branch that had split
create_checkpoint / at_interval calls
Now with --ctx-checkpoints-interval N, all checkpoint creation is
throttled to at most 1 per N positions regardless of the transition
phase.
* DSV4 checkpoints: clarify divergence log message for models with state checkpoints
The message 'does not support partial KV reuse' was misleading for DSV4,
which now supports checkpoint-based state restoration. Split the fallback
message: models with state checkpoints (DSV4, recurrent, hybrid) now print
'no checkpoint before divergence point' instead of 'does not support
partial KV reuse', explaining that the restore failed due to missing
checkpoints at the right position, not due to lack of support.
* DSV4 checkpoints: don't erase the just-restored checkpoint
The erasure condition pos_max > pos_min_thold was equivalent to
pos_max >= pos_next, erasing any checkpoint whose data touched or
went past the current write position. The checkpoint just restored
from (pos_max == pos_next) was immediately erased, wasting a ~145 MiB
checkpoint that was perfectly valid.
Fix:
- Changed erasure condition to pos_max > pos_next (strictly greater
than the next write position). Checkpoints at exactly the current
position (pos_max == pos_next, e.g. the one we just restored from)
are kept.
- Preserved cache-aligned pos_next through the restore block so the
erasure compares against cache positions, not prompt positions
(pre-existing bug where the prompt-tokens call at line 3677
overwrote pos_next with a prompt position).
* DSV4 checkpoints: update interval gate position after restore
After a checkpoint restore, slot.checkpoint_pos was still 0 (from
slot.release()), so the interval gate in create_checkpoint_at_interval
always passed (0 + 2048 <= pos + 1), creating a new ~145 MiB checkpoint
immediately after every restore — even just 5 tokens past the restored
checkpoint's position.
Fix: set slot.checkpoint_pos = it->pos_max in both restore paths
(apply_checkpoint generic restore and batch_pending_prompt DSV4
restore). This tells the gate that a checkpoint already exists at the
restored position, and no new one is needed until another interval
(2048 tokens) has elapsed.
* Missing info
* DSV4 checkpoints: document float-reduction-order reproducibility after restore
After a checkpoint restore, the PP batch loop processes remaining tokens
sequentially from n_past_prompt in chunks of n_batch. Because the loop
is stateless with no carry-over from earlier batches, the chunk boundaries
at and after the restore point are identical to a full-reprocess control
arm. This ensures float-reduction-order reproducibility between arms
when performing correctness validation.
Addresses joelfarthing's finding on openPangu, where mismatched chunk
boundaries between restore+reprocess and full-reprocess controls caused
bit-level differences that masked actual restore bugs.
* DSV4 checkpoints: verify position after restore
After both restore paths (apply_checkpoint and DSV4 batch_pending_prompt),
verify that llama_kv_cache_seq_pos_max() matches the checkpoint's pos_max.
A size-matched but misplaced restore can silently corrupt the KV cache;
on mismatch, force a full reset.
The DSV4 path pre-sets restored = true on byte-level success, then the
position check can revert it to false. Only if (restored) proceeds with
the restored state, matching the apply_checkpoint pattern.
* DSV4 checkpoints: correct misleading comment about chunk-boundary reproducibility
* DSV4 checkpoints: add FNV-1a checksum integrity check for checkpoint data
Sanity check (pos_max): catches misplaced restores (wrong stream offset,
partial overwrite) where the byte count matches but the cache position
doesn't.
Correctness check (FNV-1a hash of serialized data): catches in-memory
corruption of the checkpoint data vector between creation and restore.
Both checks are applied in the standard (apply_checkpoint) and DSV4
(batch_pending_prompt) restore paths. A mismatch in either causes the
restore to be treated as failed, falling back to full reprocess.
File format bumped to CKPT v2 (magic 0x434b5054, version 2) with a
data_hash field per checkpoint. Old-format files (LLAMA_STATE_SEQ_MAGIC)
are still loaded: the hash is computed on load so validation works
uniformly.
* Defer checkpoint hash computation to offload creation path
The FNV-1a hash (~5-15ms per 150 MiB checkpoint) is no longer computed
during checkpoint creation. Instead, data_hash is set to 0 and
hash_computed to false. The hash is computed lazily on first access via
ensure_checkpoint_hash(), called from:
- apply_checkpoint (before the integrity check during restore)
- save_checkpoints_to_file (before writing to disk)
This removes the hash computation from the time-critical checkpoint
creation path, reducing the pause between batches.
* Reuse pre-allocated scratch buffer for checkpoint serialization
Adds a reusable std::vector<uint8_t> scratch buffer to server_context,
eliminating the per-checkpoint zero-init allocation (~150 MiB memset)
from ckpt.data.resize(). The scratch is grown on demand and handed
off to the checkpoint via swap() — a zero-copy move.
Also removes default arguments from server_prompt_checkpoint_update()
since all callers already pass every parameter explicitly.
* Compute checkpoint data hash incrementally during serialization
Instead of a second pass over the serialized buffer (costly for 145 MiB DSV4
checkpoints) or deferring to save/restore time (breaks in-memory verification),
compute the FNV-1a hash as a streaming operation during llama_state_seq_get_data.
llama_data_write_buffer gains an optional fnv_hash pointer and updates it
during write() and write_tensor_data() — the hash is computed from bytes as
they land in the output buffer, with zero extra memory reads.
The server then obtains the hash at creation time by passing &ckpt.data_hash
(pre-initialized to the FNV-1a offset basis) to llama_state_seq_get_data.
This replaces the deferred hash approach (ensure_checkpoint_hash / hash_computed)
and restores in-memory round-trip verification.
* DSV4 checkpoints: add round-trip serialization verification
After restore, re-serialize the KV cache and compare byte-for-byte against
the original checkpoint data. This directly catches serialization bugs
that produce internally-consistent but wrong values (Joel's 59/64 case:
correct position, corrupted tensor data).
The check is added to both restore paths (standard apply_checkpoint and
DSV4 batch_pending_prompt) and runs after the pos_max sanity check and
FNV-1a hash integrity check. Cost: one extra llama_state_seq_get_size +
llama_state_seq_get_data + memcmp of the checkpoint data.
* Remove dead _ckpt_max_size member
_ckpt_max_size was set by server_prompt_checkpoint_update but never read.
Removed the member, the function parameter, and the call site.
* Remove no-op resize after swap in server_prompt_checkpoint_update
After swap, ckpt.data holds the scratch buffer which was already
resized to checkpoint_size. Since n == checkpoint_size (asserted),
the resize is a no-op.
* remove dead (void)has_hash cast
The variable is actually used later (for old-format file detection),
so the unused-variable suppression cast is misleading.
* add missing const qualifiers on to_json() methods
Both server_prompt_checkpoint::to_json() and server_prompt::to_json()
were missing const, preventing use on const references.
* remove duplicate n_kept_prompt assignment in server_prompt::from_json()
n_kept_prompt was assigned twice with the same value, clobbering the
slot where n_discarded_prompt should have been read.
* remove redundant params_base parameter from create_checkpoint_at_interval()
The parameter is already accessible as a member of server_context.
All callers were passing this->params_base, so the indirection was
unnecessary.
* factor duplicated restore verification into verify_restored_checkpoint() helper
The 3-step verification (pos_max sanity, FNV-1a hash, and round-trip
memcmp) was duplicated verbatim across apply_checkpoint() and
batch_pending_prompt(). Extract it into a shared static helper with
a label parameter for context-specific log messages.
Also eliminates the pos_next save/restore dance in apply_checkpoint
by using a local variable for the prompt-limit computation, and
removes a stray commented-out debug printf.
* fix two comments: fnv1a_hash comment was misleading, erasure comment imprecise
- fnv1a_hash() is used for all checkpoint verification (not just
backward-compat file loading) — broadened the description.
- 'may contain stale per-position state' → 'its per-position state
is stale' — the erasure is unconditional when pos_max > pos_next,
so the staleness is definite, not possible.
* remove FNV-1a hash and file-format bump (perf, Joelfarthing's review feedback)
The streaming FNV-1a hash added 65 ms to checkpoint creation and 107 ms
to restore (75 MiB checkpoints; roughly double at DSV4's 145 MiB). The
pos_max sanity check alone is sufficient for catching the real failure
modes (wrong stream offset, partial overwrite), and the initial byte-
count check from llama_state_seq_set_data catches outright corruption.
Removed:
- Streaming hash from llama_data_write_buffer (fnv_hash, fnv_update)
- hash_out parameter from llama_state_seq_get_data / llama.h API
- data_hash field from server_prompt_checkpoint struct
- FNV-1a computation during checkpoint creation and verification
- CKPT v2 file format (revert to LLAMA_STATE_SEQ_MAGIC/version)
- fnv1a_hash() helper function
Kept:
- pos_max sanity check in verify_restored_checkpoint (cheap, catches
misplaced restores)
- Scratch buffer reuse via swap() in server_prompt_checkpoint_update
(pure perf win, independent of hash)
* fix: restore off-by-one in n_past calculation after checkpoint restore
size_up_to_pos(pos_max) returns the number of cached tokens at positions
STRICTLY LESS THAN pos_max (non-mtmd: min(pos_max, size)). Since the
checkpoint encodes state for positions [pos_min, pos_max], the next
position to process is pos_max + 1, not pos_max.
This matters for DSV4 whose accumulator state is not position-indexed:
reprocessing the token at pos_max would double-count it in the compressed
indexer. For recurrent models the old pos_min+1 workaround happened to
give the right answer (since pos_min == pos_max there), but using
pos_max + 1 is correct for both.
Fixes both restore paths (apply_checkpoint and DSV4 in batch_pending_prompt).
* fix: only write/read DSV4 cache section for DSV4 models
The has_dsv4_cache uint32 was emitted unconditionally, changing the
serialized state layout for every model architecture without bumping
LLAMA_STATE_SEQ_VERSION. Old state/session files (which end before
this field) would fail with 'unexpectedly reached end of file' when
read by the new code.
Fix: guard the entire DSV4 section on both write and read sides with
ctx->model.arch == LLM_ARCH_DEEPSEEK4. Non-DSV4 models see the
identical layout they always had.
* fix: validate stream_idx < n_stream in dsv4_stream_offset_size
stream_idx was only checked >= 0 via GGML_ASSERT, but never checked
against n_stream. An invalid seq_id could compute an out-of-range
tensor offset or size, leading to memory corruption.
Now asserts 0 <= stream_idx < n_stream.
* fix: scratch buffer reuse — copy instead of swap
swap(scratch) moved the written data into ckpt.data but left scratch
empty. The next call's resize would then re-allocate from scratch,
defeating the purpose.
Now copies the data (ckpt.data = scratch) so scratch retains its size
and capacity across calls. resize becomes an in-place extension when
needed rather than a fresh allocation.
* fix: restore interval<=0 = disable semantics, split unconditional paths
The interval gate was inverted: interval <= 0 opened the gate, so every
call to create_checkpoint_at_interval created a checkpoint (PP, TG,
release, speculative). This changed the documented behavior ('<=0
disable' per --help) and created extra checkpoints on every decoded
token for recurrent models.
Fix:
- create_checkpoint_at_interval returns immediately when interval <= 0
(restoring the no-op semantics from the original code)
- Unconditional paths (release, PP end, PP start with slot.do_checkpoint)
call create_checkpoint(slot) directly, matching the original layout
- Interval-gated paths (TG tokens, PP start without slot.do_checkpoint,
speculative decoding) stay behind create_checkpoint_at_interval
* fix: gate ALL checkpoint creation by interval, not just TG paths
Three call sites bypassed the interval gate by calling create_checkpoint(slot)
directly instead of create_checkpoint_at_interval(slot):
- PP batch-boundary (was creating mid-PP checkpoints at unpredictable positions)
- PP end (created a checkpoint at every end-of-prompt, even if within the interval)
- release (created a checkpoint at every release, even if just 5 tokens later)
This caused checkpoints 5 and 6 in the log to be created only 5 tokens apart
(pos_max=8488 and pos_max=8493), and checkpoint 7 at release 455 tokens later,
all with interval=2048.
The original code had all checkpoint creation gated by interval (single
create_checkpoint_at_interval function called everywhere). The 'unconditional'
paths were introduced by our earlier fix that split create_checkpoint_at_interval
into a no-op for interval<=0 — but the split was too aggressive, making release,
PP-end, and PP-batch-boundary always fire.
Fix: route all checkpoint creation through create_checkpoint_at_interval, which
already handles do_checkpoint (early return) and interval <= 0 (no-op) correctly.
create_checkpoint is now an internal helper called only from
create_checkpoint_at_interval.
Result: with interval=2048 and an 8494-token prompt, checkpoints are created at
2048, 4096, 6144, 8192 only — the original semantics.
* fix: off-by-one in checkpoint gate condition, use -1 sentinel
The gate condition 'checkpoint_pos + interval <= 1 + pos' opened one
position early for non-first intervals. With checkpoint_pos=6143,
interval=2048: 6143+2048=8191, and pos=8190 gives 8191 <= 1+8190=8191
→ TRUE, creating a checkpoint at pos_max=8190 instead of 8191.
Root cause: checkpoint_pos=0 served dual duty ('no checkpoint yet' and
'checkpoint at position 0'). The '1 +' in the condition compensated
for this at startup but overcompensated later.
Fix:
- Change checkpoint_pos from size_t to llama_pos, initialized to -1
- Drop the '1 +' — condition is now checkpoint_pos + interval <= pos
With checkpoint_pos=-1: -1+2048=2047 <= 2047 → first checkpoint after
2048 tokens (correct).
With checkpoint_pos=6143: 6143+2048=8191 <= 8190 → FALSE (no early
open), 8191 <= 8191 → TRUE (opens at correct position).
Also fixes the mixed signed/unsigned comparison that existed with
size_t checkpoint_pos vs llama_pos pos.
* perf: serialize directly into ckpt.data, drop scratch buffer
The ckpt.data = scratch copy added ~10ms to checkpoint creation
(memcpy of 145 MiB). The scratch buffer was originally introduced to
avoid per-checkpoint resize allocation, but the lazy-zero paging of
modern OSes makes the resize essentially free.
Drop the _ckpt_scratch member entirely. Serialize directly into
ckpt.data after resize — same allocation cost, no extra copy.
* fix: replace GGML_ASSERT with runtime check in dsv4_stream_offset_size
GGML_ASSERT is compiled out in release builds (NDEBUG). An invalid
non-negative seq_id from the public state API would then compute
out-of-range tensor offsets and sizes, leading to memory corruption.
Replace with a runtime conditional that logs the error and sets
safe fallback values (offset=0, size=0). The caller that reads/writes
0 bytes will fail downstream in a defined way.
* fix: restore tolerance mechanism, slot.do_checkpoint bypasses interval gate
Samuel reviewed that we removed the slot.do_checkpoint branch from PP
batch-boundary, but batch_pending_prompt still sets slot.do_checkpoint
when the tolerance threshold is reached. Nowhere checks it, so the
tolerance checkpoint for short prompts (shorter than interval) is dead.
Fix: create_checkpoint_at_interval now checks slot.do_checkpoint — if
true, the interval gate is bypassed. After a successful creation the
flag is cleared so normal interval gating resumes for subsequent
checkpoints. Also handles interval <= 0 + slot.do_checkpoint correctly:
the early-return for disabled interval is itself gated by
!slot.do_checkpoint.
* revert: erasure condition back to cur.pos_max > pos_min_thold
The change from pos_min_thold to pos_next affected all models, not just
DSV4. Revert to the original condition (cur.pos_max >= pos_next after
integer simplification) which correctly erases checkpoints at or past
the write position.
* restore unconditional release checkpoint per firecoperana review
Release is a lifecycle boundary. The interval gate is for throttling
mid-processing checkpoints; the release should always capture the final
state (when do_checkpoint is enabled).
* restore original PP batch-boundary branching per firecoperana review
The explicit slot.do_checkpoint branch in the PP batch-boundary is
restored. The tolerance bypass is removed from create_checkpoint_at_interval
since it was only ever intended for the PP batch-boundary path (the
original code checked slot.do_checkpoint exclusively there). This keeps
the tolerance mechanism from leaking into TG, PP-end, and other paths.
* restore original PP-end checkpoint condition per firecoperana review
The original created an unconditional checkpoint at PP end when tolerance
is disabled (<=0). When tolerance > 0, the tolerance mechanism in the PP
loop handles the end-of-prompt capture at the tolerance point, so no
additional PP-end checkpoint is needed.
* consolidate DSV4 restore path into apply_checkpoint per firecoperana review
The DSV4-specific restore path in batch_pending_prompt duplicated the core
logic of apply_checkpoint (search, restore, verify) with different search
conditions and missing erasure. Consolidate by:
- Adding is_state_ckpt_model flag to apply_checkpoint
- Bypassing the pos_min >= pos_min_thold guard for state-checkpoint models
(DSV4 always has pos_min=0 from no eviction, so the guard blocked entry)
- Using pos_next instead of pos_min_thold for the search condition when
is_state_ckpt_model (allows finding checkpoints at pos_max == n_past - 1)
- Differentiating the reset log message per model type
- Recomputing n_past_offset and n_discarded_prompt after apply_checkpoint
(previously handled in the DSV4-specific path)
* conditional pos_next formula
State-checkpoint models (DSV4, recurrent) use pos_max + 1 — correct
for DSV4's multi-position checkpoints where pos_min=0, po neviction
max(pos_min+1, pos_max) = pos_max, which undercounts by 1.
For recurrent models pos_min==pos_max so both formulas agree.
Non-state-checkpoint models keep the original
max(pos_min + 1, pos_max) formula unchanged.
* remove redundant n_past_offset / n_discarded_prompt after apply_checkpoint
Both n_past and n_past_prompt are shifted by the same delta from the
restored checkpoint, so the difference (n_past_offset) is unchanged.
n_discarded_prompt is not used in the critical path.
* remove redundant speculative-decoding checkpoint per firecoperana review
speculative_decoding_accept is called from within the TG generation loop
which already creates interval-gated checkpoints at n_decoded > 1 (line
4779). The inner call would double-create.
* narrow DSV4-specific search and pos_next formula to DSV4 only per firecoperana review
is_state_ckpt_model includes recurrent models (e.g. Qwen 3.6) where
pos_max < pos_next search semantics may not be appropriate. Only
DSV4 needs pos_max+1 formula and pos_next-based search threshold.
* revert divergence-reset guard to original per firecoperana review
Unnecessary wrapping of the OpenPangu-only divergence path inside
!llama_model_supports_state_checkpoints. The condition is already
specific enough (!llama_model_supports_partial_kv_reuse is
OpenPangu-only), and OpenPangu does not support state checkpoints,
so the original code was functionally identical.
* narrow guard bypass to DSV4 only per firecoperana review
Recurrent state-checkpoint models don't need the pos_min >=
pos_min_thold guard bypass — only DSV4 (which always has pos_min=0
due to no KV cache eviction) requires it.
* narrow reset log message to DSV4 only per firecoperana review
Replace remaining is_state_ckpt_model with is_dsv4 in the
do_reset log branch; remove the now-unused variable.
* cleanup: revert unnecessary newlines, spacing, and comment changes
* fix: restore partial KV reuse for DSV4 in llama_model_supports_partial_kv_reuse
DSV4 has private per-position state but uses state checkpoints to
restore after a mid-sequence divergence. The function was returning
false, causing batch_pending_prompt to reset n_past=0 before
apply_checkpoint could restore from a checkpoint, which broke the
entire checkpoint mechanism.
* Remove bloat
* Reinstate deleted comment
* replace strcmp(arch_string) with llama_model_is_deepseek4()
SamuelOliveirads added the helper upstream — cleaner and avoids
the fragile string comparison.
* inline llama_model_supports_state_checkpoints into call site
Replaced with the inline expression
llama_model_has_recurrent(model) || llama_model_is_deepseek4(model)
and removed the now-unused function from llama.h and llama-model.cpp.
* fix: GCC 13.3 variadic macro trailing comma in SLT_WRN
SLT_WRN expands to LOG_WRN with __VA_ARGS__ at the end. When no extra
args follow the format string, the dangling comma causes GCC 13.3 to
error with 'expected primary-expression before')' token. Use '%s'
pattern consistent with all other zero-arg SLT_WRN callers.
* dsv4_stream_offset_size: bool return, GGML_ASSERT on write, graceful abort on read
dsv4_stream_offset_size silently returned offset=0, size=0 for invalid
stream indices. Now returns bool — writer hard-aborts via GGML_ASSERT
(prevents writing corrupt checkpoints), reader aborts the restore via
return false (handles corrupt checkpoints gracefully).