Move unused buffers to freelist

<div class="WordSection1"><p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">As
discussedand concluded in mail thread (<a
href="http://www.postgresql.org/message-id/006f01ce34f0$d6fa8220$84ef8660$@kapila@huawei.com">http://www.postgresql.org/message-id/006f01ce34f0$d6fa8220$84ef8660$@kapila@huawei.com</a>),
formoving unused buffer’s to freelist end, </span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Ihaving implemented the idea and taken some performance
data.</span><pclass="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><p
class="MsoNormal"><spanstyle="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Inthe attached patch, bgwriter/checkpointer moves unused
(usage_count=0 && refcount = 0) buffer’s to end of freelist. I have implemented a new API
StrategyMoveBufferToFreeListEnd()to </span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif";color:#1F497D">m</span><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">ovebuffer’s to end of freelist.</span><p
class="MsoNormal"><spanstyle="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">PerformanceData :</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><pclass="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">ConfigurationDetails</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">O/S– Suse-11</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">RAM– 24GB</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Numberof Cores – 8</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">ServerConf – checkpoint_segments = 256; checkpoint_timeout =
25min, synchronous_commit = 0FF, shared_buffers = 5GB</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Pgbench– Select-only</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Scalefactor– 1200</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Time– Each run is of 20 mins</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><pclass="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Belowdata is for average 3 runs of 20 minutes</span><p
class="MsoNormal"><spanstyle="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">                       8C-8T               
16C-16T           32C-32T            64C-64T</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">HEAD              11997               8455                
4989                2757</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">AfterPatch        19807               13296              
8388                2821</span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><pclass="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Detailedeach run data is attached with mail.</span><p
class="MsoNormal"><spanstyle="color:#1F497D"> </span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Thisis just the initial data, I will collect more data based
ondifferent configuration of shared buffers and other configurations.</span><span style="color:#1F497D"></span><p
class="MsoNormal"><spanstyle="font-size:10.0pt;font-family:"Arial","sans-serif""> </span><p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Feedback/Suggesions?</span><pclass="MsoNormal"><span
style="color:#1F497D"> </span><pclass="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">With
Regards,</span><pclass="MsoNormal"><span style="font-size:10.0pt;font-family:"Arial","sans-serif"">Amit
Kapila.</span></div>