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Compressed KV disk cache via streaming LZ4 #186

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b6ead20
Add lz4 streaming compression to disk KV cache
jasontitus May 20, 2026
2eb64f4
lz4: HC1 + byte-4 NEON/SSSE3 shuffle for the disk KV codec
jasontitus May 27, 2026
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40 changes: 23 additions & 17 deletions Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -48,24 +48,24 @@ help:
ds4: ds4_cli.o ds4_help.o linenoise.o $(CORE_OBJS)
$(CC) $(CFLAGS) -o $@ ds4_cli.o ds4_help.o linenoise.o $(CORE_OBJS) $(METAL_LDLIBS)

ds4-server: ds4_server.o ds4_help.o ds4_kvstore.o rax.o $(CORE_OBJS)
$(CC) $(CFLAGS) -o $@ ds4_server.o ds4_help.o ds4_kvstore.o rax.o $(CORE_OBJS) $(METAL_LDLIBS)
ds4-server: ds4_server.o ds4_help.o ds4_kvstore.o rax.o lz4.o lz4hc.o $(CORE_OBJS)
$(CC) $(CFLAGS) -o $@ ds4_server.o ds4_help.o ds4_kvstore.o rax.o lz4.o lz4hc.o $(CORE_OBJS) $(METAL_LDLIBS)

ds4-bench: ds4_bench.o ds4_help.o $(CORE_OBJS)
$(CC) $(CFLAGS) -o $@ ds4_bench.o ds4_help.o $(CORE_OBJS) $(METAL_LDLIBS)

ds4-eval: ds4_eval.o ds4_help.o $(CORE_OBJS)
$(CC) $(CFLAGS) -o $@ ds4_eval.o ds4_help.o $(CORE_OBJS) $(METAL_LDLIBS)

ds4-agent: ds4_agent.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o $(CORE_OBJS)
$(CC) $(CFLAGS) -o $@ ds4_agent.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o $(CORE_OBJS) $(METAL_LDLIBS)
ds4-agent: ds4_agent.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o rax.o lz4.o lz4hc.o $(CORE_OBJS)
$(CC) $(CFLAGS) -o $@ ds4_agent.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o rax.o lz4.o lz4hc.o $(CORE_OBJS) $(METAL_LDLIBS)

cpu: ds4_cli_cpu.o ds4_server_cpu.o ds4_bench_cpu.o ds4_eval_cpu.o ds4_agent_cpu.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o rax.o $(CPU_CORE_OBJS)
cpu: ds4_cli_cpu.o ds4_server_cpu.o ds4_bench_cpu.o ds4_eval_cpu.o ds4_agent_cpu.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o rax.o lz4.o lz4hc.o $(CPU_CORE_OBJS)
$(CC) $(CFLAGS) -o ds4 ds4_cli_cpu.o ds4_help.o linenoise.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-server ds4_server_cpu.o ds4_help.o ds4_kvstore.o rax.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-server ds4_server_cpu.o ds4_help.o ds4_kvstore.o rax.o lz4.o lz4hc.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-bench ds4_bench_cpu.o ds4_help.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-eval ds4_eval_cpu.o ds4_help.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-agent ds4_agent_cpu.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-agent ds4_agent_cpu.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o rax.o lz4.o lz4hc.o $(CPU_CORE_OBJS) $(LDLIBS)

cuda-regression:
@echo "cuda-regression requires a CUDA build"
Expand Down Expand Up @@ -98,7 +98,7 @@ cuda:
ds4: ds4_cli.o ds4_help.o linenoise.o $(CORE_OBJS)
$(NVCC) $(NVCCFLAGS) -o $@ $^ $(CUDA_LDLIBS)

ds4-server: ds4_server.o ds4_help.o ds4_kvstore.o rax.o $(CORE_OBJS)
ds4-server: ds4_server.o ds4_help.o ds4_kvstore.o rax.o lz4.o lz4hc.o $(CORE_OBJS)
$(NVCC) $(NVCCFLAGS) -o $@ $^ $(CUDA_LDLIBS)

ds4-bench: ds4_bench.o ds4_help.o $(CORE_OBJS)
Expand All @@ -107,15 +107,15 @@ ds4-bench: ds4_bench.o ds4_help.o $(CORE_OBJS)
ds4-eval: ds4_eval.o ds4_help.o $(CORE_OBJS)
$(NVCC) $(NVCCFLAGS) -o $@ $^ $(CUDA_LDLIBS)

ds4-agent: ds4_agent.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o $(CORE_OBJS)
ds4-agent: ds4_agent.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o rax.o lz4.o lz4hc.o $(CORE_OBJS)
$(NVCC) $(NVCCFLAGS) -o $@ $^ $(CUDA_LDLIBS)

cpu: ds4_cli_cpu.o ds4_server_cpu.o ds4_bench_cpu.o ds4_eval_cpu.o ds4_agent_cpu.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o rax.o $(CPU_CORE_OBJS)
cpu: ds4_cli_cpu.o ds4_server_cpu.o ds4_bench_cpu.o ds4_eval_cpu.o ds4_agent_cpu.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o rax.o lz4.o lz4hc.o $(CPU_CORE_OBJS)
$(CC) $(CFLAGS) -o ds4 ds4_cli_cpu.o ds4_help.o linenoise.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-server ds4_server_cpu.o ds4_help.o ds4_kvstore.o rax.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-server ds4_server_cpu.o ds4_help.o ds4_kvstore.o rax.o lz4.o lz4hc.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-bench ds4_bench_cpu.o ds4_help.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-eval ds4_eval_cpu.o ds4_help.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-agent ds4_agent_cpu.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o $(CPU_CORE_OBJS) $(LDLIBS)
$(CC) $(CFLAGS) -o ds4-agent ds4_agent_cpu.o ds4_help.o ds4_web.o ds4_kvstore.o linenoise.o rax.o lz4.o lz4hc.o $(CPU_CORE_OBJS) $(LDLIBS)

cuda-regression: tests/cuda_long_context_smoke
./tests/cuda_long_context_smoke
Expand Down Expand Up @@ -148,10 +148,10 @@ ds4_agent.o: ds4_agent.c ds4.h ds4_distributed.h ds4_help.h ds4_kvstore.h ds4_we
ds4_web.o: ds4_web.c ds4_web.h
$(CC) $(CFLAGS) -c -o $@ ds4_web.c

ds4_kvstore.o: ds4_kvstore.c ds4_kvstore.h ds4.h
ds4_kvstore.o: ds4_kvstore.c ds4_kvstore.h ds4.h lz4.h lz4hc.h
$(CC) $(CFLAGS) -c -o $@ ds4_kvstore.c

ds4_test.o: tests/ds4_test.c ds4_server.c ds4.h ds4_distributed.h ds4_help.h ds4_kvstore.h rax.h
ds4_test.o: tests/ds4_test.c ds4_server.c ds4.h ds4_distributed.h ds4_help.h ds4_kvstore.h rax.h lz4.h lz4hc.h
$(CC) $(CFLAGS) -Wno-unused-function -c -o $@ tests/ds4_test.c

tests/cuda_long_context_smoke.o: tests/cuda_long_context_smoke.c ds4_gpu.h
Expand All @@ -160,6 +160,12 @@ tests/cuda_long_context_smoke.o: tests/cuda_long_context_smoke.c ds4_gpu.h
rax.o: rax.c rax.h rax_malloc.h
$(CC) $(CFLAGS) -c -o $@ rax.c

lz4.o: lz4.c lz4.h
$(CC) $(CFLAGS) -Wno-unused-function -c -o $@ lz4.c

lz4hc.o: lz4hc.c lz4hc.h lz4.h
$(CC) $(CFLAGS) -Wno-unused-function -c -o $@ lz4hc.c

linenoise.o: linenoise.c linenoise.h
$(CC) $(CFLAGS) -c -o $@ linenoise.c

Expand Down Expand Up @@ -190,11 +196,11 @@ ds4_cuda.o: ds4_cuda.cu ds4_gpu.h ds4_iq2_tables_cuda.inc
tests/cuda_long_context_smoke: tests/cuda_long_context_smoke.o ds4_cuda.o
$(NVCC) $(NVCCFLAGS) -o $@ $^ $(CUDA_LDLIBS)

ds4_test: ds4_test.o ds4_help.o ds4_kvstore.o rax.o $(CORE_OBJS)
ds4_test: ds4_test.o ds4_help.o ds4_kvstore.o rax.o lz4.o lz4hc.o $(CORE_OBJS)
ifeq ($(UNAME_S),Darwin)
$(CC) $(CFLAGS) -o $@ ds4_test.o ds4_help.o ds4_kvstore.o rax.o $(CORE_OBJS) $(METAL_LDLIBS)
$(CC) $(CFLAGS) -o $@ ds4_test.o ds4_help.o ds4_kvstore.o rax.o lz4.o lz4hc.o $(CORE_OBJS) $(METAL_LDLIBS)
else
$(NVCC) $(NVCCFLAGS) -o $@ ds4_test.o ds4_help.o ds4_kvstore.o rax.o $(CORE_OBJS) $(CUDA_LDLIBS)
$(NVCC) $(NVCCFLAGS) -o $@ ds4_test.o ds4_help.o ds4_kvstore.o rax.o lz4.o lz4hc.o $(CORE_OBJS) $(CUDA_LDLIBS)
endif

test: ds4_test ds4-eval q4k-dot-test
Expand Down
97 changes: 81 additions & 16 deletions ds4_agent.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3638,13 +3638,30 @@ static bool agent_kv_load_path(agent_worker *w, const char *path,
ok = false;
}
ds4_tokens_free(&rebuilt);
} else if (ok &&
ds4_session_load_payload(w->session, fp, hdr.payload_bytes,
load_err, sizeof(load_err)) != 0)
{
snprintf(err, err_len, "%s", load_err[0] ? load_err : "failed to load KV payload");
ds4_session_invalidate(w->session);
ok = false;
} else if (ok) {
int rc = 1;
if (hdr.codec == DS4_KVSTORE_CODEC_LZ4) {
uint64_t uncompressed_total = 0;
const int n_workers = ds4_kvstore_default_options().compression_threads;
FILE *cr = kv_lz4_reader_open(fp, hdr.payload_bytes, hdr.chunk_size,
n_workers > 0 ? n_workers : 1,
&uncompressed_total);
if (!cr) {
snprintf(load_err, sizeof(load_err), "failed to open lz4 reader");
} else {
rc = ds4_session_load_payload(w->session, cr, uncompressed_total,
load_err, sizeof(load_err));
fclose(cr);
}
} else {
rc = ds4_session_load_payload(w->session, fp, hdr.payload_bytes,
load_err, sizeof(load_err));
}
if (rc != 0) {
snprintf(err, err_len, "%s", load_err[0] ? load_err : "failed to load KV payload");
ds4_session_invalidate(w->session);
ok = false;
}
}
fclose(fp);

Expand Down Expand Up @@ -3753,25 +3770,71 @@ static bool agent_kv_save_path(agent_worker *w, const char *path,
}

uint8_t h[DS4_KVSTORE_FIXED_HEADER];
/* Header is patched with the real codec and on-disk size after the write. */
const uint8_t ext_flags = session_identity ? DS4_KVSTORE_EXT_SESSION_TITLE : 0;
ds4_kvstore_fill_header(h, (uint8_t)model_id, (uint8_t)quant_bits,
ds4_kvstore_reason_code(reason),
session_identity ? DS4_KVSTORE_EXT_SESSION_TITLE : 0,
ext_flags, DS4_KVSTORE_CODEC_NONE, 0,
(uint32_t)tokens->len, 0,
(uint32_t)ds4_session_ctx(w->session),
created_at, now, payload_bytes);
uint8_t tb[4];
ds4_kvstore_le_put32(tb, (uint32_t)text_len);

errno = 0;
const int n_workers = ds4_kvstore_default_options().compression_threads;
const uint32_t chunk_bytes = DS4_KVSTORE_DEFAULT_CHUNK_BYTES;
uint8_t codec = DS4_KVSTORE_CODEC_NONE;
uint64_t on_disk_payload = 0;
bool ok = fwrite(h, 1, sizeof(h), fp) == sizeof(h) &&
fwrite(tb, 1, sizeof(tb), fp) == sizeof(tb) &&
fwrite(text, 1, text_len, fp) == text_len &&
ds4_session_write_staged_payload(&staged, fp,
save_err, sizeof(save_err)) == 0 &&
(!session_identity ||
agent_kv_write_title_trailer(fp, session_title,
save_err, sizeof(save_err))) &&
fflush(fp) == 0;
fwrite(text, 1, text_len, fp) == text_len;
if (ok) {
const off_t payload_start = ftello(fp);
if (payload_start < 0) {
ok = false;
} else if (n_workers == 0) {
ok = ds4_session_write_staged_payload(&staged, fp,
save_err, sizeof(save_err)) == 0;
} else {
FILE *cw = kv_lz4_writer_open(fp, chunk_bytes, n_workers);
if (!cw) {
ok = false;
} else {
ok = ds4_session_write_staged_payload(&staged, cw,
save_err, sizeof(save_err)) == 0;
if (fclose(cw) != 0) ok = false;
if (ok) codec = DS4_KVSTORE_CODEC_LZ4;
}
}
const off_t payload_end = ftello(fp);
if (ok && payload_end < 0) ok = false;
if (ok) on_disk_payload = (uint64_t)(payload_end - payload_start);
}
if (ok && session_identity) {
ok = agent_kv_write_title_trailer(fp, session_title,
save_err, sizeof(save_err));
}
if (ok) ok = fflush(fp) == 0;
if (ok) {
uint8_t patched[DS4_KVSTORE_FIXED_HEADER];
const uint8_t chunk_log2 =
(codec == DS4_KVSTORE_CODEC_LZ4)
? (uint8_t)(__builtin_ctz(chunk_bytes))
: 0u;
ds4_kvstore_fill_header(patched, (uint8_t)model_id, (uint8_t)quant_bits,
ds4_kvstore_reason_code(reason),
ext_flags, codec, chunk_log2,
(uint32_t)tokens->len, 0,
(uint32_t)ds4_session_ctx(w->session),
created_at, now, on_disk_payload);
if (fseeko(fp, 0, SEEK_SET) != 0 ||
fwrite(patched, 1, sizeof(patched), fp) != sizeof(patched) ||
fflush(fp) != 0)
{
ok = false;
}
}
int saved_errno = errno;
if (fclose(fp) != 0) {
if (!saved_errno) saved_errno = errno;
Expand Down Expand Up @@ -5089,7 +5152,9 @@ static bool agent_worker_strip_session(agent_worker *w, const char *prefix,

uint8_t h[DS4_KVSTORE_FIXED_HEADER];
uint64_t now = (uint64_t)time(NULL);
ds4_kvstore_fill_header(h, hdr.model_id, hdr.quant_bits, hdr.reason, hdr.ext_flags,
ds4_kvstore_fill_header(h, hdr.model_id, hdr.quant_bits,
hdr.reason, hdr.ext_flags,
DS4_KVSTORE_CODEC_NONE, 0,
stripped_token_count, hdr.hits, hdr.ctx_size,
hdr.created_at, now, 0);
uint8_t tb[4];
Expand Down
1 change: 1 addition & 0 deletions ds4_help.c
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -315,6 +315,7 @@ static void print_kv_cache(FILE *fp, const help_colors *c) {
opt(fp, c, "--kv-cache-boundary-trim-tokens N", "Trim tail tokens for cold boundary saves. Default: 32");
opt(fp, c, "--kv-cache-boundary-align-tokens N", "Align cold boundary saves to this multiple. Default: 2048");
opt(fp, c, "--kv-cache-reject-different-quant", "Reject checkpoints written with different routed-expert quantization.");
opt(fp, c, "--kv-cache-compression-threads N", "LZ4 compressor threads for disk payload. 0 disables. Default: min(8, cpus). Env: DS4_KV_CACHE_COMPRESSION_THREADS.");
opt(fp, c, "--disable-exact-dsml-tool-replay", "Disable exact sampled DSML tool replay map.");
opt(fp, c, "--tool-memory-max-ids N", "Exact tool-call IDs kept in RAM. Default: 100000");
fputc('\n', fp);
Expand Down
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