docs: add notes on the size of the cache

notes/llama-kv-cache.md

@@ -2111,6 +2111,8 @@ So this will include only the logits that belong to the current token's sequence
 To get a feel for how this works there is a standalone example in
 [llama-att-softmax.c](../ggml/src/llama-att-softmax.c)
 
+### has_shift
+
 ### Connection/link between cells and cache tensors
 This might seem obvious but this was not clear to me initially which is why I'm adding this
 section. The `cells` member of `llama_kv_cache` is a vector of `llama_kv_cell`:
@@ -2267,5 +2269,63 @@ next 7 belong to sequence 1:
   }
 ```
 
+### Size of the cache
+We can calculate the size of the cache using the following forumula:
+
+So we have two caches one for the keys and one for the values:
+```
+K cache size = ctx.cparams.n_ctx *
+               ctx.model.hparams.n_layer *
+               ctx.model.hparams.n_head_kv(0) *
+               ctx.model.hparams.n_embd_head_k *
+               ctx.kv_self.type_k
+
+V cache size = ctx.cparams.n_ctx *
+               ctx.model.hparams.n_layer *
+               ctx.model.hparams.n_head_kv(0) *
+               ctx.model.hparams.n_embd_head_v *
+               ctx.kv_self.type_v
+```
+Lets take a concrete example:
+```console
+(gdb) p ctx.cparams.n_ctx
+$11 = 512
+(gdb) p ctx.model.hparams.n_layer
+$12 = 32
+(gdb) p ctx.model.hparams.n_head_kv(0)
+$13 = 32
+(gdb) p ctx.model.hparams.n_embd_head_k
+$14 = 128
+(gdb) p ctx.model.hparams.n_embd_head_v
+$17 = 128
+(gdb) p ctx.kv_self.type_k
+$15 = GGML_TYPE_F16
+(gdb) p ctx.kv_self.type_v
+$16 = GGML_TYPE_F16
+```
+This can also be written as just one value and then doubling that if the
+values are the same for both the keys and values:
+```console
+kv-cache size = 2 *                     // both keys and values
+                ctx.cparams.n_ctx *
+                ctx.model.hparams.n_layer *
+                ctx.model.hparams.n_head_kv(0) *
+                ctx.model.hparams.n_embd_head_k *
+                ctx.kv_self.type_k
+
+k_cache_size = 512 * 32 * 32 * 128 * 2 = 536870912 = 512MB
+```
+And for other models:
+```console
+kv-cache size = 2 * 30016 * 32 * 8 * 128 * 2 bytes
+        = 2 * 30016 * 32 * 8 * 128 * 2
+        = 3934257152
+        = 3934257152 / (1024*1024)
+        = 3,750 MB
+```
+
+
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 _wip_
+
+