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authorBrian Behlendorf <[email protected]>2018-01-08 09:52:36 -0800
committerGitHub <[email protected]>2018-01-08 09:52:36 -0800
commit0873bb6337452e3e028e40f5dad945b30deab185 (patch)
tree13f3528a48e2b1dcdbb9804689217019e8d44cda /scripts
parent390d679acdfa6a2498280a4dcd33b7600ace27ce (diff)
Fix ARC hit rate
When the compressed ARC feature was added in commit d3c2ae1 the method of reference counting in the ARC was modified. As part of this accounting change the arc_buf_add_ref() function was removed entirely. This would have be fine but the arc_buf_add_ref() function served a second undocumented purpose of updating the ARC access information when taking a hold on a dbuf. Without this logic in place a cached dbuf would not migrate its associated arc_buf_hdr_t to the MFU list. This would negatively impact the ARC hit rate, particularly on systems with a small ARC. This change reinstates the missing call to arc_access() from dbuf_hold() by implementing a new arc_buf_access() function. Reviewed-by: Giuseppe Di Natale <[email protected]> Reviewed-by: Tony Hutter <[email protected]> Reviewed-by: Tim Chase <[email protected]> Reviewed by: George Wilson <[email protected]> Reviewed-by: George Melikov <[email protected]> Signed-off-by: Brian Behlendorf <[email protected]> Closes #6171 Closes #6852 Closes #6989
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