On Nov 20, 2007 6:49 AM, abc def <[EMAIL PROTECTED]> wrote:
> Suppose in my simulation i have L1 cache and no L2.
> Now i want some request to access cache but some
> should be forced to go to network as if there is no
> L1.
> How to do this efficiently?
If you have a distinct set of uncacheable addresses, then you can just
set the UNCACHEABLE bit in the flags field of the Request object.
If you want to bypass the L1 sometimes (and sometimes not) for the
same address, then this won't work, as you might bypass the L1 when
that's where the only up-to-date copy is.
>
> In cpu.cc there is a boolean variable called do_access
> which is stated to control cache access. But in the
> code there is nothing mentioned what happens do_access
> is false:
>
> /*
> if (do_access) {
> if (!dcachePort.sendTiming(dcache_pkt)) {
> _status = DcacheRetry;
> } else {
> _status = DcacheWaitResponse;
> // memory system takes ownership of packet
> dcache_pkt = NULL;
> }
> }
> */
When do_access is false, the access is not performed. If you look a
little more carefully at how that flag is used, you'll see that it
only gets set when there's a store-conditional that is guaranteed to
fail so there's no point in even going to the cache with it.
Steve
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