<div dir="ltr">Hi,<br /><br />Following are the performance results for read write test observed with different numbers
of"<b>backend_flush_after</b>".<br /><br />1) backend_flush_after = <b>256kb</b> (32*8kb), tps = <b>10841.178815</b><br
/>2)backend_flush_after = <b>512kb</b> (64*8kb), tps = <b>11098.702707</b><br />3) backend_flush_after = <b>1MB</b>
(128*8kb),tps = <b>11434.964545</b><br />4) backend_flush_after = <b>2MB</b> (256*8kb), tps = <b>13477.089417</b><br
/><br/><br /><b>Note:</b> Above test has been performed on Unpatched master with default values for
checkpoint_flush_after,bgwriter_flush_after<br />and wal_writer_flush_after. <br /><br />With Regards,<br />Ashutosh
Sharma<br/>EnterpriseDB:<u> <a href="http://www.enterprisedb.com">http://www.enterprisedb.com</a></u><br /></div><div
class="gmail_extra"><br/><div class="gmail_quote">On Thu, May 12, 2016 at 9:20 PM, Andres Freund <span dir="ltr"><<a
href="mailto:andres@anarazel.de"target="_blank">andres@anarazel.de</a>></span> wrote:<br /><blockquote
class="gmail_quote"style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On 2016-05-12
11:27:31-0400, Robert Haas wrote:<br /> > On Thu, May 12, 2016 at 11:13 AM, Andres Freund <<a
href="mailto:andres@anarazel.de">andres@anarazel.de</a>>wrote:<br /> > > Could you run this one with a number
ofdifferent backend_flush_after<br /> > > settings? I'm suspsecting the primary issue is that the default is too
low.<br/> ><br /> > What values do you think would be good to test? Maybe provide 3 or 4<br /> > suggested
valuesto try?<br /><br /></span>0 (disabled), 16 (current default), 32, 64, 128, 256?<br /><br /> I'm suspecting that
onlybackend_flush_after_* has these negative<br /> performance implications at this point. One path is to increase
that<br/> option's default value, another is to disable only backend guided<br /> flushing. And add a strong hint that
ifyou care about predictable<br /> throughput you might want to enable it.<br /><br /> Greetings,<br /><br /> Andres
Freund<br/></blockquote></div><br /></div>