Very low rate of insert operations due to lock contention

CHANGELOG for ep-engine

 * Commit: 3311f7af9e5dec52391dd3c4b3e4a73c957dab12 (in build: 2296)

   Author: Trond Norbye

   MB-22163: Optimize get_if for value eviction

   If we're using value eviction we should be able to call

   the filter method with the meta-data stored in the hashtable

   without having to fetch the value off disk.

   Change-Id: I9850ee1679094983d22b0af0c374ac02d73fdb8a

   Reviewed-on: http://review.couchbase.org/74903

   Reviewed-by: Dave Rigby 

   Tested-by: Build Bot 

CHANGELOG for memcached

 * Commit: aef7929f01907105d4044f3e6915faae54fbbb14 (in build: 2296)

   Author: Trond Norbye

   MB-22163: Use get_if to fetch items for mutations

   Reintroduce the get_if patch for mutations. It had to be

   reverted due to ep-engine returning KEY_EEXISTS for locked

   items instead of ENGINE_LOCKED (I thought I had fixed that,

   but it turned out that was pending).

   commit badccafaa2e670719c181a9ff39ffa2add5e19d6

   Author: Trond Norbye 

   Date:   Thu Mar 9 07:48:36 2017 +0100

       MB-22163: Use get_if to fetch items for mutations

       The mutations _might_ need to preserve the xattrs from

       the previous version of a document so we want to retrieve

       only the documents which already contains xattrs.

       The motivation for moving to get_if instead of get is

       that the underlying engine may provide the metadata to

       the callback without having the actual value for the

       document in memory (whereas get() would require the

       engine to fetch the document off disk). This would

       result in a significant performance improvement in

       DGM situations where we're running with value eviction.

       For full eviction we must go to disk anyway.

   Change-Id: I4c726e717b0351afaa6bb7a22c3ee8ce2d6e1629

   Reviewed-on: http://review.couchbase.org/75143

   Tested-by: Build Bot 

   Reviewed-by: Dave Rigby 

cbc-pillowfight --spec couchbase://172.23.132.17/bucket-1 --password password --batch-size 1000 --num-items 25000000 --num-threads 24 --min-size 1024 --max-size 1024 --populate-only