DTH spent about 300M memory on Microsoft.Dnx.Runtime.Servicing.Breadcrumbs when open MVC solution

[troydai]

Open MVC solution in VS with dnx-clr-win-x86.1.0.0-beta8-15109.

Noticing that about 48% of the managed memory is of type String[] and referred by Microsoft.Dnx.Runtime.Servicing.Breadcrumbs

Snapshot:

Name                                                                                    Inc %              Inc      Inc Ct  Exc %            Exc        Exc Ct  Fold    Fold Ct
 mscorlib!String                                                                         52.2      315,924,416  3,508,660.250    52.2    315,924,416    3,508,660.250      0          0
+ mscorlib!String[] (Bytes > 1M,Ptrs,ElemSize=4)                                         48.8      295,422,304  3,272,285.500     0.0              0             0     0          0
|+ mscorlib!List<String>                                                                 48.8      295,422,304  3,272,285.500     0.0              0             0     0          0
| + Microsoft.Dnx.Runtime!Microsoft.Dnx.Runtime.Servicing.Breadcrumbs                    48.8      295,422,304  3,272,285.500     0.0              0             0     0          0
|  + [static var Microsoft.Dnx.Runtime.Servicing.Breadcrumbs.<Instance>k__BackingField]  48.8      295,422,304  3,272,285.500     0.0              0             0     0          0
|   + [static vars]                                                                      48.8      295,422,304  3,272,285.500     0.0              0             0     0          0
|    + [.NET Roots]                                                                      48.8      295,422,304  3,272,285.500     0.0              0             0     0          0
|     + ROOT                                                                             48.8      295,422,304  3,272,285.500     0.0              0             0     0          0

[davidfowl]

Hah! Nice catch! This is an easy one to fix

[troydai]

Observation Note

1. PackageDependencyProvider keeps adding breadcrumbs throughout the entire life cycle. see here
2. Since that the PackageDependencyProvider adding breadcrumbs each time GetDescription is called, there are duplicate value in the _breadcrumbsToWrite list. It can be replaced by an HashSet. see here
3. Set $env:DNX_NO_BREADCRUMBS=1, then the breadcrumbs memory consumption completely disappeared.

I'll begin prototyping some fix.

/cc @davidfowl @victorhurdugaci @rynowak

[rynowak]

😻