FindMarkers with the 'lr' test uses all cores despite changing future::plan()

[jmrussell]

FindMarkers is defaulting to use all cores when running using the 'LR' test (and poisson for that matter) which is probably fine except on shared resources. The future vignette hasn't been updated since 2019, but presumably FindMarkers should respect future::plan("sequential") or setting the number of workers with future::plan("multisession", workers = 12) when called before invoking the function and that doesn't appear to be the case.

Is there another function in differential_expression.R that uses parallel cores outside of the future_sapply in LRDETest()? If so, it would be nice to know what it is and how to prevent it from using all cores.

This is on Seurat 4.30, which loads future 1.33.0, future.apply 1.11.0 and

library(future)
future::plan("sequential")

plan()
#  sequential:
# - args: function (..., envir = parent.frame())
# - tweaked: FALSE
# - call: future::plan("sequential")

markers <- FindMarkers(obj, ident.1 = 147, only.pos = TRUE,
  test.use = 'LR',latent.vars = 'atac_peak_region_fragments',
  logfc.threshold = 2, min.pct=0.05)