[0/2] generic_file_buffered_read() refactoring, perf improvements

Message

Kent Overstreet Oct. 17, 2020, 8:10 p.m. UTC

Rebased this patchset onto 5.9, I'd like to finally get this because
generic_file_buffered_read() has turned into a real monstrosity to work with.
And it's a major performance improvement, for both small random and large
sequential reads. On my test box, 4k buffered random reads go from ~150k to
~250k iops, and the improvements to big sequential reads are even bigger.

This incorporates the fix for IOCB_WAITQ handling that Jens just posted as well,
also factors out lock_page_for_iocb() to improve handling of the various iocb
flags.

Kent Overstreet (2):
  fs: Break generic_file_buffered_read up into multiple functions
  fs: generic_file_buffered_read() now uses find_get_pages_contig

 mm/filemap.c | 563 ++++++++++++++++++++++++++++++---------------------
 1 file changed, 328 insertions(+), 235 deletions(-)