[Rd] Memory leakage from large lists

[Daniel Raduta]

Hello,

I am experiencing a very noticeable memory leak when using large lists of
large data. The code below creates a list of matrices, yet the memory does
not free up after removing that item and performing a garbage collection.
Is there a something I can do to prevent this memory leak? Any help would
be greatly appreciated. By the way, if you execute the code, please run it
in a new R session.

# Start of code
================================================================

# Function that returns memory being used
MemoryUsed <- function(){
  pid <- Sys.getpid()
  system(paste0("top -n 1 -p ", pid, " -b"), intern = TRUE)[c(7,8)]
}

# Initial memory (VIRT memory equals about 400,000 bytes on my machine)
MemoryUsed()

# Create a large list of large data, remove it, and perform garbarge
collection
ncols <- 100
nrows <- 10000
mat <- matrix(seq(nrows * ncols), nrow = nrows, ncol = ncols)
ls <- lapply(1:1000, function(x) as.data.frame(mat))
rm(list = setdiff(ls(), 'MemoryUsed'))
invisible(gc())

# Final memory (now, VIRT memory equals about 4,600,000 bytes on my machine)
MemoryUsed()

# End of code
==================================================================

My session info is:

R version 3.4.4 (2018-03-15)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 16.04.3 LTS

Matrix products: default
BLAS: /usr/lib/libblas/libblas.so.3.6.0
LAPACK: /usr/lib/lapack/liblapack.so.3.6.0

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8
LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

loaded via a namespace (and not attached):
[1] compiler_3.4.4 tools_3.4.4    yaml_2.1.19

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