gem5 ruby中的L2 latency

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下面是本人使用gem5 ruby过程中遇到的问题：

1. 在使用ruby过程中，笔者采用protocol:MESI_CMP_directory编译和运行，运行后的

输出有config.ini, ruby.stats, 以及stats.txt三个文件，一切正常；

然后，我修改MESI_CMP_directory.py:

class L2Cache(RubyCache):

latency = 15

将上述的latency = 15 修改为 20,我本来期望看到性能的差别，即stats.txt中的sim_ticks中

看到明显增加，因为l2的latency增加了嘛，但是实际上在l2的latency的修改前后，两者的值

一样，没有差别；

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另外在修改L2的latency后，运行产生的config.ini的确显示l2的latency为20;

网上搜了下，看到下面的内容：

https://www.mail-archive.com/gem5-users@gem5.org/msg06258.html

HI Jordan,

The protocol files themselves specified latencies for the different

ports, rather than pulling them from the config files. For example in

the MESI_CMP_directory-L1cache.sm file:

 int l2_select_num_bits,

 int l1_request_latency = 2,

 int l1_response_latency = 2,

 int to_l2_latency = 1,

these variables are used to indicate the latency of a protocol message

when it is enqueued to a port. Thus, each port for the same cache

could have different access latencies.

Malek

On Fri, Dec 21, 2012 at 5:14 PM, Jordan Fix <j...@cs.princeton.edu> wrote:

> Hello,

> I'm doing simulations with the Ruby memory system. I found a comment in

> configs/ruby/MESI_CMP_directory.py that says:

> "# Note: the L2 Cache latency is not currently used"

> Does this mean that the ruby memory system for MESI_CMP_directory is not

> timing accurate when going to the L2? What about latency when going to main

> memory?

> Thanks.

原来l2 cache的延时并没有在性能计算中被使用到，难怪我前面修改latency从15ns 到 20ns，并没有明显效果。

那要产生效果的话，应该根据实际需要，修改MESI_CMP_directory-L2cache.sm中的相关参数和过程。

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