ExecutionManager::GetRangeSection performs a linear search over list of loaded assemblies

[briansull]

PerfView indicates that significant time can be spent in this method when we create a Delegate:
The MusicStore application has over 130 managed assemblies loaded.
Eliminating this search can improve steady state transaction time by ~3%

|+ coreclr!COMDelegate::DelegateConstruct
We have to perform two IP lookups in DelegateConstruct

       FCIMPL3(void, COMDelegate::DelegateConstruct, Object* refThisUNSAFE, Object* targetUNSAFE, PCODE method)
(line 1914)
219.0 |    MethodDesc * pCreatorMethod = ExecutionManager::GetCodeMethodDesc((PCODE)pRetAddr);
(line 1933)
159.0 |    MethodDesc *pMethOrig = Entry2MethodDesc(method, pRealMT);

Both of these calls eventually resolve to: ExecutionManager::GetRangeSection

RangeSection* ExecutionManager::GetRangeSection(TADDR addr)
. . . 
          while (pCurr != NULL)
           {
               // See if addr is in [pCurr->LowAddress .. pCurr->HighAddress)
 12.0 |        if (pCurr->LowAddress <= addr)
               {
                   // Since we are sorted, once pCurr->HighAddress is less than addr
                   // then all subsequence ones will also be lower, so we are done.
  3.0 |            if (addr >= pCurr->HighAddress)
                   {
                       // we'll return NULL and put pLast into pLastUsed
                       pCurr = NULL;
                   }
                   else
                   {
                       // addr must be in [pCurr->LowAddress .. pCurr->HighAddress)
                       _ASSERTE((pCurr->LowAddress <= addr) && (addr < pCurr->HighAddress));
       
                       // Found the matching RangeSection
                       // we'll return pCurr and put it into pLastUsed
                       pLast = pCurr;
                   }
       
                   break;
               }
320.0 |        pLast = pCurr;
 57.0 |        pCurr = pCurr->pnext;
           }

[briansull]

@vancem Issue filed

[briansull]

@jkotas FYI, these delegate lookups cost us 3% of execution time in MusicStore (when everything is crossgened) because we have loaded over 140 managed assemblies (native imgaes) and the linear search becomes a problem.

[AndyAyersMS]

It looks like in CoreCLR the first range lookup is actually no longer needed. In desktop this lookup feeds secure delegate creation. That use has been removed in Core, but the lookup remains.

So maybe we can get half of this perf back very cheaply.

    void* pRetAddr = _ReturnAddress();
    pCreatorMethod = ExecutionManager::GetCodeMethodDesc((PCODE)pRetAddr);
    // pCreatorMethod unused after this

[AndyAyersMS]

Might be more we could do here but the Range data structure is fundamental so it would require careful thought. Moving to future.

[ghost]

Due to lack of recent activity, this issue has been marked as a candidate for backlog cleanup. It will be closed if no further activity occurs within 14 more days. Any new comment (by anyone, not necessarily the author) will undo this process.

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[jkotas]

This should stay open.

[davidwrighton]

I'm looking at a fix for this.