mirror of
https://github.com/RetroPortingToolKit/psxrecomp
synced 2026-10-28 10:59:16 -04:00
Alex Vanderveen
75 lines
3.0 KiB
C
75 lines
3.0 KiB
C
/*
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* netplay_ram_dirty.h -- page-dirty tracking for the per-tick RAM digest.
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*
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* netplay_core_digest_parts used to CRC the full guest RAM (2 MiB, 8 MiB with
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* the RAM mod) EVERY tick in BOTH the client and the link follower — ~0.8 ms
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* a tick of pure hashing per process against a 20 ms PAL budget. This module
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* keeps a per-4KiB-page CRC cache: stores mark their page dirty (one test +
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* one OR on the already-chokepointed store path, see memory.c), the digest
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* re-hashes only dirty pages and folds the page-CRC array.
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*
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* The RAM partition digest value therefore CHANGES (fold-of-page-CRCs instead
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* of one linear CRC). That is safe: nothing persists it and it is only ever
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* compared between same-build peers (see crc32.c's contract note and the
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* netplay_state_digest.c consumers).
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*
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* Tracking self-arms on the first digest call (marks everything dirty), so
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* offline play never pays the per-store cost. Bulk writers that bypass the
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* store chokepoint (savestate/rollback RAM restore, overlay shadow restore,
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* RAM bank switch) must call np_ram_dig_mark_all(); see the call sites.
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*
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* A periodic self-check re-hashes every page and screams if a cached CRC is
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* stale (i.e. some writer path is missing a mark) — then heals. Cadence via
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* PSX_NP_RAM_DIG_VERIFY (digest calls between checks; 0 disables; default
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* 1024 ≈ 20 s of netplay).
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*/
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#ifndef NETPLAY_RAM_DIRTY_H
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#define NETPLAY_RAM_DIRTY_H
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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#define NP_RAM_DIG_PAGE_SHIFT 12u /* 4 KiB */
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#define NP_RAM_DIG_MAX_BYTES (8u << 20) /* 8 MiB RAM mod */
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#define NP_RAM_DIG_MAX_PAGES (NP_RAM_DIG_MAX_BYTES >> NP_RAM_DIG_PAGE_SHIFT)
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extern int g_np_ram_dig_tracking;
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extern uint32_t g_np_ram_dig_dirty[NP_RAM_DIG_MAX_PAGES / 32u];
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/* Store chokepoint mark: a few ops, off until the first digest call. phys is
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* the RAM-relative offset (caller already range-checked it). Aligned word /
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* half stores never straddle a 4 KiB page, so one mark suffices. */
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static inline void np_ram_dig_note_write(uint32_t phys) {
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if (!g_np_ram_dig_tracking) return;
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{
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uint32_t pg = phys >> NP_RAM_DIG_PAGE_SHIFT;
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g_np_ram_dig_dirty[pg >> 5u] |= 1u << (pg & 31u);
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}
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}
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static inline void np_ram_dig_note_range(uint32_t phys, uint32_t len) {
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if (!g_np_ram_dig_tracking || len == 0u) return;
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{
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uint32_t pg = phys >> NP_RAM_DIG_PAGE_SHIFT;
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uint32_t pg_end = (phys + len - 1u) >> NP_RAM_DIG_PAGE_SHIFT;
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for (; pg <= pg_end && pg < NP_RAM_DIG_MAX_PAGES; pg++)
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g_np_ram_dig_dirty[pg >> 5u] |= 1u << (pg & 31u);
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}
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}
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/* Every page recomputes on the next digest. For writers that bypass the
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* store chokepoint (full-RAM restore, bank switch, shadow restore). */
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void np_ram_dig_mark_all(void);
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/* The RAM partition digest: raw (un-finalized, crc32_update convention)
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* CRC over the page-CRC array, dirty pages re-hashed first. */
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uint32_t np_ram_dig_crc_raw(const uint8_t *ram, uint32_t bytes);
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#ifdef __cplusplus
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}
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#endif
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#endif /* NETPLAY_RAM_DIRTY_H */
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