CVS commit: src/sys/uvm

["Jaromir Dolecek" <jdolecek%netbsd.org@localhost>]

Module Name:    src
Committed By:   jdolecek
Date:           Sat May 19 15:18:02 UTC 2018

Modified Files:
        src/sys/uvm: uvm_readahead.c

Log Message:
adjust heuristics for read-ahead to skip the full read-ahead when last page of
the range is already cached; this speeds up I/O from cache, since it avoids
the lookup and allocation overhead

on my system I observed 4.5% - 15% improvement for cached I/O - from 2.2 GB/s to
2.3 GB/s for cached reads using non-direct UBC, and from 5.6 GB/s to 6.5 GB/s
for UBC using direct map

part of PR kern/53124


To generate a diff of this commit:
cvs rdiff -u -r1.9 -r1.10 src/sys/uvm/uvm_readahead.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.