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Commit7584974

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baronfelTIHan
authored andcommitted
TcSymbolUseData cleanup perdotnet#6084 (dotnet#6089)
* chunkify TcSymbolUseData* move LOH size out to a constant* do chunking and mapping together to reduce allocations* clarify comment around GC impacts* add comment informing others of the potential for LOH allocations
1 parentce59d48 commit7584974

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4 files changed

+68
-12
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4 files changed

+68
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lines changed

‎src/absil/illib.fs‎

Lines changed: 48 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -41,6 +41,10 @@ let inline isNonNull x = not (isNull x)
4141
let inlinenonNull msg x=if isNull xthen failwith("null:"+ msg)else x
4242
let inline(===) x y= LanguagePrimitives.PhysicalEquality x y
4343

44+
/// Per the docs the threshold for the Large Object Heap is 85000 bytes: https://docs.microsoft.com/en-us/dotnet/standard/garbage-collection/large-object-heap#how-an-object-ends-up-on-the-large-object-heap-and-how-gc-handles-them
45+
/// We set the limit to slightly under that to allow for some 'slop'
46+
letLOH_SIZE_THRESHOLD_BYTES=84_900
47+
4448
//---------------------------------------------------------------------
4549
// Library: ReportTime
4650
//---------------------------------------------------------------------
@@ -91,7 +95,7 @@ module Order =
9195
lettoFunction(pxOrder:IComparer<'U>)x y= pxOrder.Compare(x,y)
9296

9397
//-------------------------------------------------------------------------
94-
// Library: arrays,lists,options
98+
// Library: arrays,lists,options,resizearrays
9599
//-------------------------------------------------------------------------
96100

97101
moduleArray=
@@ -432,6 +436,49 @@ module List =
432436
letexistsSquared f xss= xss|> List.exists(fun xs-> xs|> List.exists(fun x-> f x))
433437
letmapiFoldSquared f z xss= mapFoldSquared f z(xss|> mapiSquared(fun i j x->(i,j,x)))
434438

439+
moduleResizeArray=
440+
441+
/// Split a ResizeArray into an array of smaller chunks.
442+
/// This requires `items/chunkSize` Array copies of length `chunkSize` if `items/chunkSize % 0 = 0`,
443+
/// otherwise `items/chunkSize + 1` Array copies.
444+
letchunkBySize chunkSize f(items:ResizeArray<'t>)=
445+
// we could use Seq.chunkBySize here, but that would involve many enumerator.MoveNext() calls that we can sidestep with a bit of math
446+
letitemCount= items.Count
447+
if itemCount=0
448+
then[||]
449+
else
450+
letchunksCount=
451+
match itemCount/ chunkSizewith
452+
| nwhen itemCount% chunkSize=0-> n
453+
| n-> n+1// any remainder means we need an additional chunk to store it
454+
455+
[|for indexin0..chunksCount-1do
456+
letstartIndex= index* chunkSize
457+
lettakeCount= min(itemCount- startIndex) chunkSize
458+
459+
letholder= Array.zeroCreate takeCount
460+
// we take a bounds-check hit here on each access.
461+
// other alternatives here include
462+
// * iterating across an IEnumerator (incurs MoveNext penalty)
463+
// * doing a block copy using `List.CopyTo(index, array, index, count)` (requires more copies to do the mapping)
464+
// none are significantly better.
465+
for iin0.. takeCount-1do
466+
holder.[i]<- f items.[i]
467+
yield holder|]
468+
469+
/// Split a large ResizeArray into a series of array chunks that are each under the Large Object Heap limit.
470+
/// This is done to help prevent a stop-the-world collection of the single large array, instead allowing for a greater
471+
/// probability of smaller collections. Stop-the-world is still possible, just less likely.
472+
letmapToSmallArrayChunks f(inp:ResizeArray<'t>)=
473+
letitemSizeBytes= sizeof<'t>
474+
// rounding down here is good because it ensures we don't go over
475+
letmaxArrayItemCount= LOH_SIZE_THRESHOLD_BYTES/ itemSizeBytes
476+
477+
/// chunk the provided input into arrays that are smaller than the LOH limit
478+
/// in order to prevent long-term storage of those values
479+
chunkBySize maxArrayItemCount f inp
480+
481+
435482
/// Because FSharp.Compiler.Service is a library that will target FSharp.Core 4.5.2 for the forseeable future,
436483
/// we need to stick these functions in this module rather than using the module functions for ValueOption
437484
/// that come after FSharp.Core 4.5.2.

‎src/fsharp/NameResolution.fs‎

Lines changed: 14 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1212,7 +1212,7 @@ let GetNestedTypesOfType (ad, ncenv:NameResolver, optFilter, staticResInfo, chec
12121212
//-------------------------------------------------------------------------
12131213

12141214
/// Represents the kind of the occurrence when reporting a name in name resolution
1215-
[<RequireQualifiedAccess>]
1215+
[<RequireQualifiedAccess; Struct>]
12161216
typeItemOccurence=
12171217
/// This is a binding / declaration of the item
12181218
| Binding
@@ -1496,17 +1496,24 @@ type TcSymbolUseData =
14961496
/// This is a memory-critical data structure - allocations of this data structure and its immediate contents
14971497
/// is one of the highest memory long-lived data structures in typical uses of IDEs. Not many of these objects
14981498
/// are allocated (one per file), but they are large because the allUsesOfAllSymbols array is large.
1499-
typeTcSymbolUses(g, capturedNameResolutions:ResizeArray<CapturedNameResolution>,formatSpecifierLocations:(range*int)[])=
1500-
1499+
typeTcSymbolUses(g, capturedNameResolutions:ResizeArray<CapturedNameResolution>,formatSpecifierLocations:(range*int)[])=
1500+
15011501
// Make sure we only capture the information we really need to report symbol uses
1502-
letallUsesOfSymbols=[|for cnrin capturedNameResolutions->{ Item=cnr.Item; ItemOccurence=cnr.ItemOccurence; DisplayEnv=cnr.DisplayEnv; Range=cnr.Range}|]
1502+
letallUsesOfSymbols=
1503+
capturedNameResolutions
1504+
|> ResizeArray.mapToSmallArrayChunks(fun cnr->{ Item=cnr.Item; ItemOccurence=cnr.ItemOccurence; DisplayEnv=cnr.DisplayEnv; Range=cnr.Range})
1505+
15031506
letcapturedNameResolutions=()
15041507
do ignore capturedNameResolutions// don't capture this!
15051508

15061509
memberthis.GetUsesOfSymbol(item)=
1507-
[|for symbolUsein allUsesOfSymbolsdo
1508-
if protectAssemblyExplorationfalse(fun()-> ItemsAreEffectivelyEqual g item symbolUse.Item)then
1509-
yield symbolUse|]
1510+
// This member returns what is potentially a very large array, which may approach the size constraints of the Large Object Heap.
1511+
// This is unlikely in practice, though, because we filter down the set of all symbol uses to those specifically for the given `item`.
1512+
// Consequently we have a much lesser chance of ending up with an array large enough to be promoted to the LOH.
1513+
[|for symbolUseChunkin allUsesOfSymbolsdo
1514+
for symbolUsein symbolUseChunkdo
1515+
if protectAssemblyExplorationfalse(fun()-> ItemsAreEffectivelyEqual g item symbolUse.Item)then
1516+
yield symbolUse|]
15101517

15111518
memberthis.AllUsesOfSymbols= allUsesOfSymbols
15121519

‎src/fsharp/NameResolution.fsi‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -240,7 +240,7 @@ type TypeNameResolutionInfo =
240240
static memberResolveToTypeRefs:TypeNameResolutionStaticArgsInfo->TypeNameResolutionInfo
241241

242242
/// Represents the kind of the occurrence when reporting a name in name resolution
243-
[<RequireQualifiedAccess>]
243+
[<RequireQualifiedAccess; Struct>]
244244
type internal ItemOccurence=
245245
| Binding
246246
| Use
@@ -319,7 +319,7 @@ type internal TcSymbolUses =
319319
memberGetUsesOfSymbol:Item->TcSymbolUseData[]
320320

321321
/// All the uses of all items within the file
322-
memberAllUsesOfSymbols:TcSymbolUseData[]
322+
memberAllUsesOfSymbols:TcSymbolUseData[][]
323323

324324
/// Get the locations of all the printf format specifiers in the file
325325
memberGetFormatSpecifierLocationsAndArity:unit->(range* int)[]

‎src/fsharp/service/service.fs‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1917,7 +1917,8 @@ type FSharpCheckProjectResults(projectFileName:string, tcConfigOption, keepAssem
19171917
letcenv= SymbolEnv(tcGlobals, thisCcu, Some ccuSig, tcImports)
19181918

19191919
[|for rin tcSymbolUsesdo
1920-
for symbolUsein r.AllUsesOfSymbolsdo
1920+
for symbolUseChunkin r.AllUsesOfSymbolsdo
1921+
for symbolUsein symbolUseChunkdo
19211922
if symbolUse.ItemOccurence<> ItemOccurence.RelatedTextthen
19221923
letsymbol= FSharpSymbol.Create(cenv, symbolUse.Item)
19231924
yield FSharpSymbolUse(tcGlobals, symbolUse.DisplayEnv, symbol, symbolUse.ItemOccurence, symbolUse.Range)|]
@@ -2111,7 +2112,8 @@ type FSharpCheckFileResults(filename: string, errors: FSharpErrorInfo[], scopeOp
21112112
(fun()->[||])
21122113
(fun scope->
21132114
letcenv= scope.SymbolEnv
2114-
[|for symbolUsein scope.ScopeSymbolUses.AllUsesOfSymbolsdo
2115+
[|for symbolUseChunkin scope.ScopeSymbolUses.AllUsesOfSymbolsdo
2116+
for symbolUsein symbolUseChunkdo
21152117
if symbolUse.ItemOccurence<> ItemOccurence.RelatedTextthen
21162118
letsymbol= FSharpSymbol.Create(cenv, symbolUse.Item)
21172119
yield FSharpSymbolUse(scope.TcGlobals, symbolUse.DisplayEnv, symbol, symbolUse.ItemOccurence, symbolUse.Range)|])

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