Mach messages: iocompressionstats_notification

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osfmk/mach/iocompressionstats_notification.defs. Service/callback interface outside the ordinary kernel kobject table. Follow local sender/receiver evidence; external service bodies are not supplied by the declaration. Registration evidence: mig_e.

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IDs are computed from the explicit preprocessing profiles in the catalog guide, counting both routines and skip slots. They are not discovered from a running kernel. Each entry retains all observed names/declaration locations; the displayed fields come from the first non-skipped profile. Alternative declarations can have different fields. simpleroutine is one-way at the MIG interface level.

An interface contract block quotes the adjacent local .defs comment with whitespace normalized. Mechanism paragraphs explain selected implementation decisions. Local body links and call names identify implementation evidence; syntactic call lists are reading aids, not a proof that every listed call executes on every path. Short complete implementation bodies are included where especially useful.

Complete routine and reserved-slot catalog

5600: iocompressionstats_notification

Send the declared I/O compression statistics to an external notification receiver.

Mechanism: The VFS statistics sender obtains the host compression-statistics service port, sends notice value zero and releases the right; unavailable endpoints cause an early return. The message prompts userspace processing of collected statistics rather than carrying a complete compressed buffer or performing file compression. Local path.

Declarations: iocompressionstats_notification (server64, server32, client64, client32, libsyscall64, sender64, local64).

Fields after preprocessing (server64):

simpleroutine iocompressionstats_notification(
 RequestPort iocompressionstats_port : mach_port_t;
 in flags : uint32_t);

Implementation boundary: no same-symbol receiver body was resolved in the indexed local C/C++ implementation files. Local source occurrences to follow: bsd/vfs/vfs_io_compression_stats.c:424. These may be senders, wrappers or declarations; they do not establish a local receiver.