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Re: [cdt-dev] EDC and asynchronous operations

Felix and Eugene,

One thing I'm finding challenging about ACPM is managing the lifetime of cache objects. These things must live beyond the lifetime of the transaction that uses them since otherwise the transaction will perpetually fail. And when the transaction eventually completes successfully, it's beneficial to not discard the cache objects since there might be a transaction around the corner that needs the same data. At the same time, you don't want to keep piling up the cache objects indefinitely, for obvious memory footprint and performance reasons. So, I've been coding up a manager that tries to take these things into consideration. Did you guys have the same challenge with tcf-debug? Just wanted to check that there isn't some simplistic approach that's not becoming obvious to me.

John

At 04:23 PM 10/12/2010, Burton, Felix wrote:
Regarding 1: I don¬ít understand what you mean.  The following is simplified pseudo code that count number of frame on a stack by following a frame pointer list.
 
Boolean countStackFrames(Context ctx) {
                TCFDataCache<Register> fp = lookupRegisterCI(ctx, REGISTER_FP);
                if (!fp.validate(this)) {
                                fp.wait(this);
                                return false;
                }
                Address addr = fp.getData().valueAsAddress();
                long count = 0;
                while (addr != 0) {
                                TCFDataCache<Memory> mem = lookupMemoryCI(ctx, addr, address_size);
                                if (!mem.validate(this)) {
                                                mem.wait(this);
                                                return false;
                                }
                                addr = mem.getData().valueAsAddress();
                                count++;
                }
                set(null, null, count);
                return true;
}
 
Regarding 2: I agree, we are not proposing that the asynchronous API should expose ACPM objects like cache instances.  Cache instances can be built on top of an asynchronous API to allow client to use ACPM instead of directly using the asynchronous API.  This is reflected on page 1 in the attached slides.  The TCF box on the bottom is exposing asynchronous APIs and on top of that are cache instances that expose ACPM APIs and on top of that is client code, e.g. code that assembles information that goes into a view, another cache instance, or other client.
 
Hope this helps,
Felix
 
From: cdt-dev-bounces@xxxxxxxxxxx [ mailto:cdt-dev-bounces@xxxxxxxxxxx] On Behalf Of John Cortell
Sent: Tuesday, October 12, 2010 1:41 PM
To: CDT General developers list.; CDT General developerslist.
Subject: Re: [cdt-dev] EDC and asynchronous operations
 
At 02:47 PM 10/12/2010, Burton, Felix wrote:

Felix, everything you wrote makes sense to me. Again, I definitely see the advantages of ACPM for the client of an async API that needs to make many API calls to carry out an operation. My points have been

1. ACPM is suitable only if you know the superset of all the data points your operation will need. There are many situations where this won't be the case.

2. ACPM seems to me a good tool for the client of an asynchronous API. However, It's not clear to me that an asynchronous API should expose ACPM objects, which I think is what Pawel was hinting at.

John

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