From a9e3760b0838299649c0d57cca44daaf40ba3c33 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 14 Sep 2026 22:12:34 -1000 Subject: sched_ext: Maintain an online cid mask in the scheduler arena Schedulers on the default cid mapping treat [0, nr_online_cids) as the online set and restart on hotplug. Schedulers that install their own mapping with scx_bpf_cid_override() have no way to learn which cids are online: the count no longer identifies members and the CPU-form cpumask is unusable from cid programs. This is an obvious hole in the cid API. Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's arena, allocated alongside the per-CPU scratch masks and populated after the cid mapping is finalized and before ops.init(), for child schedulers too. The pointer stays valid through ops.exit() with no reference to take. It is the arena offset as a void pointer, the same form struct_ops arena arguments arrive in. The verifier types the void return as a scalar for the program's arena cast. The mask follows the SCX hotplug notifications: seeded from cpu_active_mask and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask only inside a hotplug transition. Updates walk the scheduler list under the lock that also serializes unlinking. Reads are live, not atomic snapshots. Root initialization excludes hotplug. v2: Reworded the getter kerneldoc (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- tools/perf/util/zstd.c | 149 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) create mode 100644 tools/perf/util/zstd.c (limited to 'tools/perf/util/zstd.c') diff --git a/tools/perf/util/zstd.c b/tools/perf/util/zstd.c new file mode 100644 index 000000000..21a0eb585 --- /dev/null +++ b/tools/perf/util/zstd.c @@ -0,0 +1,149 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include + +#include "util/compress.h" +#include "util/debug.h" + +int zstd_init(struct zstd_data *data, int level) +{ + data->comp_level = level; + data->dstream = NULL; + data->cstream = NULL; + return 0; +} + +int zstd_fini(struct zstd_data *data) +{ + if (data->dstream) { + ZSTD_freeDStream(data->dstream); + data->dstream = NULL; + } + + if (data->cstream) { + ZSTD_freeCStream(data->cstream); + data->cstream = NULL; + } + + return 0; +} + +ssize_t zstd_compress_stream_to_records(struct zstd_data *data, void *dst, size_t dst_size, + void *src, size_t src_size, size_t max_record_size, + size_t process_header(void *record, size_t increment)) +{ + size_t ret, size, compressed = 0; + ZSTD_inBuffer input = { src, src_size, 0 }; + ZSTD_outBuffer output; + void *record; + + if (!data->cstream) { + data->cstream = ZSTD_createCStream(); + if (data->cstream == NULL) { + pr_err("Couldn't create compression stream.\n"); + return -1; + } + + ret = ZSTD_initCStream(data->cstream, data->comp_level); + if (ZSTD_isError(ret)) { + pr_err("Failed to initialize compression stream: %s\n", + ZSTD_getErrorName(ret)); + return -1; + } + } + + while (input.pos < input.size) { + record = dst; + /* process_header writes the event header into record */ + if (dst_size < sizeof(struct perf_event_header)) + goto reset; + size = process_header(record, 0); + /* Output buffer full — cannot fit even the record header */ + if (size > dst_size) + goto reset; + compressed += size; + dst += size; + dst_size -= size; + output = (ZSTD_outBuffer){ dst, (dst_size > max_record_size) ? + max_record_size : dst_size, 0 }; + ret = ZSTD_compressStream(data->cstream, &output, &input); + ZSTD_flushStream(data->cstream, &output); + if (ZSTD_isError(ret)) { + pr_err("failed to compress %ld bytes: %s\n", + (long)src_size, ZSTD_getErrorName(ret)); + goto reset; + } + size = output.pos; + /* + * No progress: ZSTD couldn't emit any bytes into the + * remaining output buffer. Calling process_header + * with size=0 would re-trigger header initialization, + * double-subtracting the header size from dst_size and + * underflowing the unsigned counter. + */ + if (size == 0) + goto reset; + size = process_header(record, size); + compressed += size; + dst += size; + dst_size -= size; + } + + return compressed; + +reset: + /* Reset so the context is usable if the caller retries */ + ret = ZSTD_initCStream(data->cstream, data->comp_level); + if (ZSTD_isError(ret)) + pr_err("failed to reset compression context: %s\n", + ZSTD_getErrorName(ret)); + return -1; +} + +size_t zstd_decompress_stream(struct zstd_data *data, void *src, size_t src_size, + void *dst, size_t dst_size) +{ + size_t ret; + ZSTD_inBuffer input = { src, src_size, 0 }; + ZSTD_outBuffer output = { dst, dst_size, 0 }; + + if (!data->dstream) { + data->dstream = ZSTD_createDStream(); + if (data->dstream == NULL) { + pr_err("Couldn't create decompression stream.\n"); + return 0; + } + + ret = ZSTD_initDStream(data->dstream); + if (ZSTD_isError(ret)) { + pr_err("Failed to initialize decompression stream: %s\n", + ZSTD_getErrorName(ret)); + return 0; + } + } + while (input.pos < input.size) { + size_t prev_in = input.pos; + size_t prev_out = output.pos; + + ret = ZSTD_decompressStream(data->dstream, &output, &input); + if (ZSTD_isError(ret)) { + pr_err("failed to decompress (B): %zd -> %zd, dst_size %zd : %s\n", + src_size, output.pos, dst_size, ZSTD_getErrorName(ret)); + return 0; + } + /* + * Neither stream advanced — decompression is stuck. + * Return 0 (error) rather than partial output: perf + * uses ZSTD_flushStream (not ZSTD_endStream), so the + * stream is continuous across compressed events. + * Discarding unconsumed input would desynchronize the + * decompressor, causing the next call to produce + * garbage that could be misinterpreted as valid events. + */ + if (input.pos == prev_in && output.pos == prev_out) + return 0; + } + + return output.pos; +} -- cgit v1.3.1