If the memcmp returns 0, the pages are equal and a match is found.
如果memcmp返回0，则页面相同，发现一个匹配值。
A memcmp (memory compare) operation is performed on the page and node's page of consideration.
一个memcmp(内存比较)操作将在该页面和相关节点的页面上执行。
Although comparing 4kb pages seems fairly heavyweight, in most cases, the memcmp will end prematurely once a difference is found.
尽管比较4kb的页面似乎是相当重量级的比较，但是在多数情况下，一旦发现一个差异，memcmp将提前结束。
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