git: tmpfs - Flush and recycle pages quickly during heavy paging activity

[Matthew Dillon]

commit cfd59c5a2b3edde0431e7578d5c63f4600f8a262
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date:   Wed Feb 12 12:47:07 2020 -0800

    tmpfs - Flush and recycle pages quickly during heavy paging activity
    
    * When the pagedaemon is operating any write()s made via tmpfs will
      be forced to operate through the buffer cache via cluster_write()
      or bdwrite() instead of using buwrite().
    
      This will cause the pages to be pipelined to backing store (swap)
      under these conditions, making them clean immediately to avoid
      having tmpfs cause further paging pressure on the system when it
      is already under paging pressure.
    
    * In addition, the B_TTC flag is set on these buffers to attempt to
      recycle the pages directly into PQ_CACHE ASAP after they are flushed.
    
    * Implement cluster_write() operation by default to try to improve
      block sizes for physical I/O.
    
    * TMPFS currently must move pages between two VM objects when
      reclaiming a vnode, and back again upon re-use.  The current
      VM mechanism for renaming VM pages dirties them and this can
      potentially cause the paging system to thrash on the same page
      under heavy vnode recycling loads.
    
      Instead of allowing this to happen, TMPFS now frees any clean
      page that have backing store assigned when moving from the backing
      object, and any clean pages that were instantiated from backing
      store when moving to the backing object.

Summary of changes:
 sys/vfs/tmpfs/tmpfs_vnops.c | 111 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 93 insertions(+), 18 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/cfd59c5a2b3edde0431e7578d5c63f4600f8a262


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