This patch adds support for "asyncForce" which forces all pages to disk that
were dirtied before the *previous* call call to asyncForce. This method
only applies to dirty pages in the Linux file cache (not in the Stasis buffer
pool), and is used by new writeback logic that bounds the amount of such
backlog that exists at any given time.
This patch also changes writeback behavior; the dirty page table now sorts
pages by pageid instead of LSN when it is invoked by writeback. When it is
invoked by log truncation, it still sorts by LSN.
This commit should significantly improve sequential write thoughput.
I found a segfault bug this morning, but cannot reproduce. Could be a heisenbug, or could have been a hardware fault (gojira repeatedly kernel paniced, then both problems went away...)
