GHC.Stats

This module provides access to internal garbage collection and memory usage statistics. These statistics are not available unless a program is run with the -T RTS flag.

This module is GHC-only and should not be considered portable.

Since: 4.5.0.0

Documentation

data GCStats

Global garbage collection and memory statistics.

Since: 4.5.0.0

Constructors

GCStats

Fields

• bytesAllocated :: !Int64

  Total number of bytes allocated

• numGcs :: !Int64

  Number of garbage collections performed

• maxBytesUsed :: !Int64

  Maximum number of live bytes seen so far

• numByteUsageSamples :: !Int64

  Number of byte usage samples taken | Sum of all byte usage samples, can be used with numByteUsageSamples to calculate averages with arbitrary weighting (if you are sampling this record multiple times).

• cumulativeBytesUsed :: !Int64
• bytesCopied :: !Int64

  Number of bytes copied during GC

• currentBytesUsed :: !Int64

  Current number of live bytes

• currentBytesSlop :: !Int64

  Current number of bytes lost to slop

• maxBytesSlop :: !Int64

  Maximum number of bytes lost to slop at any one time so far

• peakMegabytesAllocated :: !Int64

  Maximum number of megabytes allocated | CPU time spent running mutator threads. This does not include any profiling overhead or initialization.

• mutatorCpuSeconds :: !Double
• mutatorWallSeconds :: !Double

  Wall clock time spent running mutator threads. This does not include initialization.

• gcCpuSeconds :: !Double

  CPU time spent running GC

• gcWallSeconds :: !Double

  Wall clock time spent running GC

• cpuSeconds :: !Double

  Total CPU time elapsed since program start

• wallSeconds :: !Double

  Total wall clock time elapsed since start | Number of bytes copied during GC, minus space held by mutable lists held by the capabilities. Can be used with parMaxBytesCopied to determine how well parallel GC utilized all cores.

• parTotBytesCopied :: !Int64
• parMaxBytesCopied :: !Int64

  Sum of number of bytes copied each GC by the most active GC thread each GC. The ratio of parTotBytesCopied divided by parMaxBytesCopied approaches 1 for a maximally sequential run and approaches the number of threads (set by the RTS flag -N) for a maximally parallel run.

Instances

Read GCStats

Methods

readsPrec :: Int -> ReadS GCStats

readList :: ReadS [GCStats]

readPrec :: ReadPrec GCStats

readListPrec :: ReadPrec [GCStats]

Show GCStats

Methods

showsPrec :: Int -> GCStats -> ShowS

show :: GCStats -> String

showList :: [GCStats] -> ShowS

getGCStats :: IO GCStats

Retrieves garbage collection and memory statistics as of the last garbage collection. If you would like your statistics as recent as possible, first run a performGC.

Since: 4.5.0.0

getGCStatsEnabled :: IO Bool

Returns whether GC stats have been enabled (with +RTS -T, for example).

Since: 4.6.0.0