feat(core): runtime-toggleable memory-mapped file I/O (MMapEnabled) - #565
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Fix the CMake wiring so mmap is actually reachable (amule-project#34): the port never set HAVE_MMAP (glib21.cmake probed munmap, not mmap) and never passed ENABLE_MMAP to the compiler, so USE_MMAP was dead on every CMake build even with -DENABLE_MMAP=YES. Add the missing mmap/sigaction probes and a single MMAP_SUPPORTED capability macro (set when mmap/munmap/sysconf/_SC_PAGESIZE/ sigaction are all present) gating the code path, the preferences checkbox and the EC tag. ENABLE_MMAP becomes a default-ON build opt-out (no external dependency; all libc). Make mmap use a runtime preference (MMapEnabled, default OFF): - CFileArea reads an atomic flag at ReadAt/StartWriteAt; the per-area mode is captured in m_mmap_buffer so FlushAt/Close stay state-driven -- safe to flip live with active downloads and uploads (in-flight blocks finish in their original mode). - The SIGSEGV/SIGBUS recovery handler installs once, when mmap is first enabled, rather than per read/write and never when off, so it cannot collide with sanitizers/debuggers/crash reporters. - Advanced-tab checkbox; capability negotiated over EC (EC_TAG_FILES_MMAP_ SUPPORTED/_ENABLED) so amulegui/amulecmd/amuleweb/amuleapi show the toggle only when the connected daemon supports mmap (tag-presence == capability; works cross-platform, e.g. Windows GUI to a Linux daemon). Relax the 4 GiB per-area cap (forum 16444): it only guards a 32-bit off_t. On 64-bit off_t -- every modern LFS build, including 32-bit-with-LFS (aMule inherits _FILE_OFFSET_BITS=64 from wx) -- mmap handles large offsets natively, verified against a >4 GiB region, so large files get mmap for their whole length; the cap remains only for a (wx-precluded) non-LFS 32-bit build.
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July 23, 2026 17:14
This was referenced Jul 23, 2026
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Follow-up to #565: surface the memory-mapped file I/O preference on the REST API. files.mmap_supported is a read-only daemon capability (mirrors upnp_available), read from the EC_TAG_FILES_MMAP_SUPPORTED tag; files.mmap_enabled is the runtime value. A PATCH that sets mmap_enabled is rejected with 409 when the connected daemon lacks mmap support, so the option is only writable against a core that can actually use it. Updates docs/api/REFERENCE.md and the 15-preferences-patch curl smoke (round-trip on a mmap-capable daemon; the 409 capability gate otherwise).
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Summary
Makes memory-mapped part-file I/O a runtime preference (
MMapEnabled, default OFF) instead of a compile-time feature, and fixes the CMake wiring that made mmap unreachable in the first place (#34).The #34 root cause
mmap was dead code in every CMake build:
glib21.cmakeprobedmunmapbut nevermmap, soHAVE_MMAPwas never set, andENABLE_MMAPwas never passed to the compiler — soUSE_MMAPcould never be true even with-DENABLE_MMAP=YES. This adds the missingmmap/sigactionprobes and a singleMMAP_SUPPORTEDcapability macro (set whenmmap+munmap+sysconf+_SC_PAGESIZE+sigactionare all present) that gates the code path, the preferences checkbox, and the EC tag.ENABLE_MMAPbecomes a default-ON build opt-out (no external dependency — all libc).Runtime toggle
CFileAreareads an atomic flag inReadAt/StartWriteAt; the per-area mode is captured inm_mmap_buffer, soFlushAt/Closestay state-driven. Safe to flip live with active downloads and uploads — an in-flight block always finishes in its original mode.EC_TAG_FILES_MMAP_SUPPORTED/_ENABLED) so amulegui/amulecmd/amuleweb/amuleapi show the toggle only when the connected daemon supports mmap (tag-presence == capability; works cross-platform, e.g. a Windows GUI driving a Linux daemon).4 GiB cap (forum 16444)
Relaxed: the
offEnd < 4 GiBguard only matters with a 32-bitoff_t. On 64-bitoff_t— every modern LFS build, including 32-bit-with-LFS (aMule inherits_FILE_OFFSET_BITS=64from wx) — mmap handles large offsets natively, verified against a >4 GiB region (write via mmap, read-back viapread, 0 mismatches). So large files now get mmap for their whole length; the cap remains only for a (wx-precluded) non-LFS 32-bit build.Testing
Builds clean across monolithic/amulegui/amuled/amulecmd; clang-format + clang-tidy (both tiers) clean. Runtime functional testing (mmap activation + RSS drop; remote show/hide over EC) is in progress — draft until that's done.