Skip site navigation (1) Skip section navigation (2)

Re: Posix Shared Mem patch

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Cc: Josh Berkus <josh(at)agliodbs(dot)com>
Subject: Re: Posix Shared Mem patch
Date: 2012-06-29 19:52:39
Message-ID: 201206292152.40311.andres@2ndquadrant.com (view raw or flat)
Thread:
Lists: pgsql-hackers
Hi All,

In a *very* quick patch I tested using huge pages/MAP_HUGETLB for the mmap'ed 
memory.
That gives around 9.5% performance benefit in a read-only pgbench run (-n -S -
j 64 -c 64 -T 10 -M prepared, scale 200, 6GB s_b, 8 cores, 24GB mem).

It also saves a bunch of memory per process due to the smaller page table 
(shared_buffers 6GB):
cat /proc/$pid_of_pg_backend/status |grep VmPTE
VmPTE:	    6252 kB
vs
VmPTE:	      60 kB

Additionally it has the advantage that top/ps/... output under linux now looks 
like:                                                                        
  PID USER      PR  NI  VIRT  RES  SHR S  %CPU %MEM    TIME+  COMMAND 
10603 andres    20   0 6381m 4924 1952 R    21  0.0   0:28.04 postgres  

i.e. RES now actually shows something usable... Which is rather nice imo.

I don't have the time atm into making this something useable, maybe somebody 
else want to pick it up? Looks pretty worthwile investing some time.

Because of the required setup we sure cannot make this the default but...

Greetings,

Andres
-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Attachment: hugetlb.diff
Description: text/x-patch (836 bytes)

In response to

Responses

pgsql-hackers by date

Next:From: Merlin MoncureDate: 2012-06-29 20:00:01
Subject: Re: Posix Shared Mem patch
Previous:From: Bruce MomjianDate: 2012-06-29 19:35:31
Subject: Re: new --maintenance-db options

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group