git: sbin/hammer: Move cache to tailq end when get_buffer_data() has a valid cache

[Tomohiro Kusumi]

commit 63eacb74267a5a2776a215b529ab1a6f6939b80b
Author: Tomohiro Kusumi <kusumi.tomohiro at gmail.com>
Date:   Sun Jul 2 21:30:08 2017 +0300

    sbin/hammer: Move cache to tailq end when get_buffer_data() has a valid cache
    
    This is the same as what get_buffer() does when new allocation
    is not needed. This hasn't been done in get_buffer_data() when
    the given non NULL buffer is the one to look for.
    
    This seems to make newfs_hammer a bit faster, as the i/o size is
    normally large enough to invoke eviction of HAMMER userspace buffer
    cache while running, starting from the head of the tailq.
    
    -- before this commit
     # for x in 1 2 3 4 5; do
     > (time newfs_hammer -L TEST /dev/da1 /dev/da2 /dev/da3 > /dev/null) 2>&1 | grep real
     > done
     real    0m20.291s
     real    0m20.574s
     real    0m22.347s
     real    0m21.562s
     real    0m20.991s
    
    -- with this commit
     # for x in 1 2 3 4 5; do
     > (time newfs_hammer -L TEST /dev/da1 /dev/da2 /dev/da3 > /dev/null) 2>&1 | grep real
     > done
     real    0m18.023s
     real    0m18.064s
     real    0m18.104s
     real    0m17.646s
     real    0m18.310s

Summary of changes:
 sbin/hammer/ondisk.c | 2 ++
 1 file changed, 2 insertions(+)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/63eacb74267a5a2776a215b529ab1a6f6939b80b


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