diff --git a/patch_v2/reader_app/engine/rdft.c b/patch_v2/reader_app/engine/rdft.c
index 73b1a3f..7b4ad54 100644
--- a/patch_v2/reader_app/engine/rdft.c
+++ b/patch_v2/reader_app/engine/rdft.c
@@ -15,6 +15,13 @@ typedef struct {
     int          bw, bh, pitch, left, top;
 } glyph_slot;
 
+/* advance 测量缓存：rdft_advance 逐字测量是排版索引用热路径（大书每次开/重排全量逐字测），
+ * 同一码点在全书反复出现（中文常用字 ~几千）。独立的小型开放寻址表缓存 (px,cp)→advance，
+ * 避免对重复码点反复 FT_Load_Glyph，把测量成本从 O(全书字符) 摊到 O(唯一码点)。
+ * 与 glyph_slot 缓存分离：glyph 缓存存「已光栅化位图」，此处只存 advance（不栅格化、不占位图）。 */
+#define RD_ADV_SLOTS 4096    /* 幂 2；开放寻址线性探测 */
+typedef struct { uint64_t key; int adv; } adv_slot;
+
 struct rdft {
     FT_Library    lib;
     FT_Face       face;
@@ -23,6 +30,7 @@ struct rdft {
     int           nslots;    /* 容量 */
     int           used;      /* 在线条目数 */
     uint64_t      clock;     /* 单调戳 */
+    adv_slot     *adv;       /* advance 缓存（排版测量） */
     int           has_font;
 };
 
@@ -36,6 +44,8 @@ int rdft_init(rdft **r)
     x->nslots = 512;
     x->slots = (glyph_slot *)calloc((size_t)x->nslots, sizeof(glyph_slot));
     if (!x->slots) { FT_Done_FreeType(x->lib); free(x); return -6; }
+    x->adv = (adv_slot *)calloc(RD_ADV_SLOTS, sizeof(adv_slot));
+    if (!x->adv) { free(x->slots); FT_Done_FreeType(x->lib); free(x); return -6; }
     x->used = 0;
     x->clock = 1;
     *r = x;
@@ -48,6 +58,7 @@ int rdft_load_font(rdft *r, const char *path)
     if (r->face) { FT_Done_Face(r->face); r->face = NULL; }
     if (r->slots) { for (int i = 0; i < r->nslots; i++) free(r->slots[i].bmp); }
     if (r->slots) memset(r->slots, 0, (size_t)r->nslots * sizeof(glyph_slot));
+    if (r->adv) memset(r->adv, 0, (size_t)RD_ADV_SLOTS * sizeof(adv_slot));
     r->used = 0;
     if (FT_New_Face(r->lib, path, 0, &r->face) != 0) { r->has_font = 0; return -1; }
     r->has_font = 1;
@@ -61,8 +72,9 @@ void rdft_set_px(rdft *r, int px)
     if (px <= 0) px = r->px;
     r->px = px;
     if (r->face) FT_Set_Pixel_Sizes(r->face, 0, (FT_UInt)px);
-    /* key 含字号，清缓存防旧字号位图残留 */
+    /* key 含字号，清缓存防旧字号位图残留（glyph + advance 同清，key 同含 px） */
     if (r->slots) { for (int i = 0; i < r->nslots; i++) free(r->slots[i].bmp); memset(r->slots, 0, (size_t)r->nslots * sizeof(glyph_slot)); }
+    if (r->adv) memset(r->adv, 0, (size_t)RD_ADV_SLOTS * sizeof(adv_slot));
     r->used = 0;
 }
 
@@ -147,18 +159,53 @@ int rdft_glyph(rdft *r, uint32_t cp, int *adv_x,
     return 0;
 }
 
+/* (px,cp)→advance 缓存：开放寻址线性探测；key==0 为空槽哨兵（key=(px<<32)|cp，px≥1 恒非 0）。 */
+static uint32_t adv_hash(uint64_t key)
+{
+    /* 乘法散列取高位，把 64 位 key（px 在高位、cp 在低位）散布到 12 位表。 */
+    return (uint32_t)((key * 2654435761ULL) >> 22) & (RD_ADV_SLOTS - 1);
+}
+static int adv_find(const rdft *r, uint64_t key, int *adv)
+{
+    uint32_t h = adv_hash(key);
+    for (uint32_t i = 0; i < RD_ADV_SLOTS; i++) {
+        uint32_t idx = (h + i) & (RD_ADV_SLOTS - 1);
+        uint64_t k = r->adv[idx].key;
+        if (k == 0) return 0;
+        if (k == key) { *adv = r->adv[idx].adv; return 1; }
+    }
+    return 0;
+}
+static void adv_put(rdft *r, uint64_t key, int adv)
+{
+    uint32_t h = adv_hash(key);
+    for (uint32_t i = 0; i < RD_ADV_SLOTS; i++) {
+        uint32_t idx = (h + i) & (RD_ADV_SLOTS - 1);
+        if (r->adv[idx].key == 0 || r->adv[idx].key == key) {
+            r->adv[idx].key = key; r->adv[idx].adv = adv; return;
+        }
+    }
+    /* 表满：丢弃（下次未命中直接算） */
+}
+
 int rdft_advance(rdft *r, uint32_t cp, int *adv_x)
 {
     if (!r || !r->face || !adv_x) return -1;
+    uint64_t key = ((uint64_t)(uint32_t)r->px << 32) | cp;
+    if (adv_find(r, key, adv_x)) return 0;
     FT_UInt gi = FT_Get_Char_Index(r->face, cp);
     if (r->px <= 0) FT_Set_Pixel_Sizes(r->face, 0, (FT_UInt)r->px);
     if (FT_Load_Glyph(r->face, gi, FT_LOAD_NO_HINTING | FT_LOAD_TARGET_LIGHT) != 0) {
-        *adv_x = r->face->glyph->advance.x >> 6;
+        int a = r->face->glyph->advance.x >> 6;
+        *adv_x = a;
+        adv_put(r, key, a);
         return 0;
     }
     int a = (int)((r->face->glyph->advance.x >= 0 ? r->face->glyph->advance.x + 0x20
                                                   : r->face->glyph->advance.x - 0x20) >> 6);
-    *adv_x = a < 0 ? 0 : a;
+    a = a < 0 ? 0 : a;
+    *adv_x = a;
+    adv_put(r, key, a);
     return 0;
 }
 
@@ -209,6 +256,7 @@ void rdft_free(rdft *r)
     if (!r) return;
     if (r->slots) { for (int i = 0; i < r->nslots; i++) free(r->slots[i].bmp); }
     free(r->slots);
+    free(r->adv);
     if (r->face) FT_Done_Face(r->face);
     if (r->lib) FT_Done_FreeType(r->lib);
     free(r);