fastaFromBed execution is slower for first run and subsequent runs are faster

[rjg2186]

Hi @brentp , @jashapiro , @nachocab , @wac , @lindenb Recently, I have been using bedtools fastaFromBed on hg38 fasta with index file to extract around 15000 sequences based on BED file in google cloud VM. The first run for the day or first run after long time gap (example > 8 hours), takes more time (around 23 seconds), but the subsequent immediate runs (within 15 or 20 or 60 minutes), takes only 2 or 3 seconds with same genome and BED file. Is there anything related to genome files being stored in cache or how it works ? If I try to use another genome index, for eample mm10 with index fai file, again the first run takes more time. But when I execute the same command with same input file and index file in local linux, all runs are very consistent for the total time of execution. Please provide your inputs on this. Thanks