行缓存堆需求（Cassandra 1.0） [英] Row Cache Heap Requirements (Cassandra 1.0)

问题描述

我已经测试了行缓存，并发现，它需要大量的堆 - 我想验证这个理论。

I've tested row cache, and find out, that it requires large amount of Heap - I would like to verify this theory.

这是我的测试键空格：
{
TestCF：{

This is my test key space: { TestCF: {

    row_key_1: {
        { clientKey: "MyTestCluientKey" },
        { tokenSecret: "kd94hf93k423kf44" },
        { verifier: "hfdp7dh39dks9884" },
        { callbackUrl: "http%3A%2F%2Fprinter.test.com%2Fready" },
        { accountId: "234567876545"},
        { mytestResourceId: "ADB112"},
        { dataTimestamp: "1308903420400" },
        { dataType: "ACCESS_PERMANENT"}
    },
    row_key_2: {
        { clientKey: "MyTestCluientKey" },
        { tokenSecret: "qdqergvhetyhvetyh" },
        { verifier: "wtrgvebyjnrnuiucewrqxcc" },
        { callbackUrl: "http%3A%2F%2Fprinter.test.com%2Fready" },
        { accountId: "23456789746534"},
        { mytestResourceId: "DQERGCWRTHB"},
        { dataTimestamp: "130890342333200" },
        { dataType: "ACCESS_LIMITED"}
    },

...
row_key_x：{
....
}，

... row_key_x: { .... },

}

}

CF：TestCF包含8列。行高速缓存已启用，密钥高速缓存已禁用。行命中率0.99 - 这是只读测试。

Each row in CF: TestCF contains 8 columns. Row cache is enabled, key cache is disabled. Row hit rate 0.99 - this is read only test.

我的测试加载了1.500.000行到缓存 - 这分配了大约3.5GB的堆 - 这是大约2KB pro单

My test loads 1.500.000 rows into cache - and this allocates about 3.5GB heap - this is about 2KB pro single row - this is a lot....

有可能，单行（8列）可以分配大约2KB的堆？

Is it possible, that single row (8 columns) can allocate about 2KB heap?

谢谢你，
Maciej

Thank you, Maciej

推荐答案

是的，经验法则是memtable或行缓存将需要大约8x到12x的序列化大小。这是一个原因，如果您安装了JNA，则离线缓存是1.0中的默认值：off-heap以序列化形式存储行。

Yes, rule of thumb is that a row in a memtable or row cache will take about 8x to 12x its serialized size. This is one reason the off-heap cache is the default in 1.0 if you have JNA installed: off-heap stores the rows in serialized form.

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