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Detect GC pressure

Source: R/antipatterns.R
pv_gc_pressure.Rd

Analyzes the profile to detect excessive garbage collection, which is a universal indicator of memory allocation issues in R code.

Usage

pv_gc_pressure(x, threshold = 10)

Arguments

x

A profvis object.

threshold

Minimum GC percentage to report (default 10). Set lower to detect smaller GC overhead.

Value

A data frame with columns:

  • severity: "high" (>25%), "medium" (>15%), or "low" (>threshold%)

  • pct: Percentage of total time spent in GC

  • time_ms: Time spent in garbage collection

  • issue: Short description of the problem

  • cause: What typically causes this issue

  • actions: Comma-separated list of things to look for

Returns an empty data frame (0 rows) if GC is below the threshold.

Details

GC pressure above 10% typically indicates the code is allocating and discarding memory faster than necessary. Common causes include:

  • Growing vectors with c(x, new) instead of pre-allocation

  • Building data frames row-by-row with rbind()

  • Creating unnecessary copies of large objects

  • String concatenation in loops

Examples

p <- pv_example("gc")
pv_gc_pressure(p)
#>   severity pct time_ms                    issue                       cause
#> 1     high  40      40 High GC overhead (40.0%) Excessive memory allocation
#>                                                        actions
#> 1 growing vectors, repeated data frame ops, unnecessary copies

# More sensitive detection
pv_gc_pressure(p, threshold = 5)
#>   severity pct time_ms                    issue                       cause
#> 1     high  40      40 High GC overhead (40.0%) Excessive memory allocation
#>                                                        actions
#> 1 growing vectors, repeated data frame ops, unnecessary copies

# No GC pressure in default example
p2 <- pv_example()
pv_gc_pressure(p2)
#> [1] severity pct      time_ms  issue    cause    actions 
#> <0 rows> (or 0-length row.names)