Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-14 Thread Ivan Voras
 Date: Sun, 12 Oct 2003 13:30:45 -0700
 From: Josh Berkus [EMAIL PROTECTED]
 To: Nick Barr [EMAIL PROTECTED]
 Cc: [EMAIL PROTECTED]
 Subject: Re: go for a script! / ex:  PostgreSQL vs. MySQL
 Message-ID: [EMAIL PROTECTED]


 This would be parameters such as the block size and a few other
 compile time parameters. If we can get to some of these read-only
 parameters than that would make this step easier, certainly for the new
 recruits amongst us.

 Actually, from my perspective, we shouldn't bother with this; if an admin
 knows enough to set an alternate blaock size for PG, then they know
 enough to tweak the Conf file by hand.  I think we should just issue a
 warning that this script:
 1) does not work for anyone who is using non-default block sizes,

There was some talk, either on this list or freebsd-performance about
setting the default block size for PostgreSQL running on FreeBSD to be 16k
because of performance reasons. That is: *default* for the port, user is not
asked. So an automagical method to scale non-default block sizes is a very
needed thing.

 2) may not work well for anyone using unusual locales, optimization
 flags, or other non-default compile options except for language
 interfaces.

Depends on what you consider 'unusual'? I hope not things like iso8859-x
(or, to be exact, European languages) :)


--
Logic is a systematic method of coming to the wrong conclusion with
confidence.


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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-14 Thread Josh Berkus
Ivan,

 There was some talk, either on this list or freebsd-performance about
 setting the default block size for PostgreSQL running on FreeBSD to be 16k
 because of performance reasons. That is: *default* for the port, user is
 not asked. So an automagical method to scale non-default block sizes is a
 very needed thing.

Hmmm ... possibly.   My concern is that if someone uses a very non-default 
value, such as 256K, then they are probably better off doing their own tuning 
because they've got an unusual system.  However, we could easily limit it to 
the range of 4K to 32K.

Of course, since there's no GUC var, we'd have to ask the user to confirm 
their block size.  I'm reluctant to take this approach because if the user 
gets it wrong, then the settings will be *way* off ... and possibly cause 
PostgreSQL to be unrunnable or have out of memory crashes.

Unless there's a way to find it in the compiled source?

  2) may not work well for anyone using unusual locales, optimization
  flags, or other non-default compile options except for language
  interfaces.

 Depends on what you consider 'unusual'? I hope not things like iso8859-x
 (or, to be exact, European languages) :)

On second thought, I'm not sure what an unusual locale would be.  Scratch 
that.

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-14 Thread Tom Lane
Josh Berkus [EMAIL PROTECTED] writes:
 Unless there's a way to find it in the compiled source?

See pg_controldata.

regards, tom lane

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-14 Thread Sean Chittenden
  This would be parameters such as the block size and a few
  other compile time parameters. If we can get to some of these
  read-only parameters than that would make this step easier,
  certainly for the new recruits amongst us.
 
  Actually, from my perspective, we shouldn't bother with this; if an admin
  knows enough to set an alternate blaock size for PG, then they know
  enough to tweak the Conf file by hand.  I think we should just issue a
  warning that this script:
  1) does not work for anyone who is using non-default block sizes,
 
 There was some talk, either on this list or freebsd-performance
 about setting the default block size for PostgreSQL running on
 FreeBSD to be 16k because of performance reasons. That is: *default*
 for the port, user is not asked.

Real quick, this isn't true, the block size is tunable, but does not
change the default.  You can set PGBLOCKSIZE to the values 16K or
32K to change the block size, but the default remains 8K.

http://lists.freebsd.org/pipermail/freebsd-database/2003-October/000111.html

-sc

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Vivek Khera
 SC == Sean Chittenden [EMAIL PROTECTED] writes:

 echo effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))
 
 I've used it for my dedicated servers.  Is this calculation correct?

SC Yes, or it's real close at least.  vfs.hibufspace is the amount of
SC kernel space that's used for caching IO operations (minus the

I'm just curious if anyone has a tip to increase the amount of memory
FreeBSD will use for the cache?  It appears to me that even on my 2Gb
box, lots of memory is 'free' that could be used for the cache
(bumping up shared buffers is another option...) yet the disk is being
highly utilized according to systat.

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Shridhar Daithankar
On Monday 13 October 2003 19:34, Vivek Khera wrote:
  SC == Sean Chittenden [EMAIL PROTECTED] writes:
 
  echo effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))
 
  I've used it for my dedicated servers.  Is this calculation correct?

 SC Yes, or it's real close at least.  vfs.hibufspace is the amount of
 SC kernel space that's used for caching IO operations (minus the

 I'm just curious if anyone has a tip to increase the amount of memory
 FreeBSD will use for the cache?  It appears to me that even on my 2Gb
 box, lots of memory is 'free' that could be used for the cache
 (bumping up shared buffers is another option...) yet the disk is being
 highly utilized according to systat.

Is this of any help?..reverse video sucks though.. especially spec'ed person 
like me..

http://unix.derkeiler.com/Mailing-Lists/FreeBSD/performance/2003-07/0073.html

 Shridhar


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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Sean Chittenden
  echo effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))
  
  I've used it for my dedicated servers.  Is this calculation correct?
 
 SC Yes, or it's real close at least.  vfs.hibufspace is the amount
 of SC kernel space that's used for caching IO operations (minus the
 
 I'm just curious if anyone has a tip to increase the amount of
 memory FreeBSD will use for the cache?

Recompile your kernel with BKVASIZE set to 4 times its current value
and double your nbuf size.  According to Bruce Evans:

Actually there is a way: the vfs_maxbufspace gives the amount of
space reserved for buffer kva (= nbuf * BKVASIZE).  nbuf is easy to
recover from this, and the buffer kva space may be what is wanted
anyway.
[snip]
I've never found setting nbuf useful, however.  I want most
parametrized sizes including nbuf to scale with resource sizes, and
it's only with RAM sizes of similar sizes to the total virtual address
size that its hard to get things to fit.  I haven't hit this problem
myself since my largest machine has only 1GB.  I use an nbuf of
something like twice the default one, and a BKVASIZE of 4 times the
default.  vfs.maxbufspace ends up at 445MB on the machine with 1GB, so
it is maxed out now.

YMMV.

-sc

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Sean Chittenden
   PostgreSQL requires some more shared memory to cache some
   tables, x Mb, do you want to increase your OS kernel parameters?
  
  Tweak shmmax and shmmall
 
  Note that this still requires a kernel recompile on FreeBSD :(
 
 Not our fault, now is it?  This would mean that we wouldn't be able
 to script for FreeBSD.  Bug the FreeBSD developers.

And if you do so, you're going to hear that shm* is an antiquated
interface that's dated, slow, inefficient and shouldn't be used.  :)

Every few months one of the uber core BSD hackers threatens to rewrite
that part of PG because high up in the BSD camp, it's common belief
that shm* is a source of performance loss for PostgreSQL.  One of
these days it'll happen, probably with mmap() mmap()'ing MAP_SHARED
files stored in a $PGDATA/data/shared dir as mmap() is by far and away
the fastest shared memory mechanism and certainly is very widely
deployed (I would be surprised if any of the supported PG platforms
didn't have mmap()).

-sc

-- 
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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Vivek Khera
 JB == Josh Berkus [EMAIL PROTECTED] writes:

JB Chris,
  PostgreSQL requires some more shared memory to cache some tables, x Mb,
  do you want to increase your OS kernel parameters?
 
 Tweak shmmax and shmmall
 
 Note that this still requires a kernel recompile on FreeBSD :(

JB Not our fault, now is it?  This would mean that we wouldn't be
JB able to script for FreeBSD.  Bug the FreeBSD developers.

I read it on the net so it must be true applies here.  You /can/ set
these values via sysctl calls.

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Vivek Khera, Ph.D.Khera Communications, Inc.
Internet: [EMAIL PROTECTED]   Rockville, MD   +1-240-453-8497
AIM: vivekkhera Y!: vivek_khera   http://www.khera.org/~vivek/

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Vivek Khera
 CK == Christopher Kings-Lynne [EMAIL PROTECTED] writes:

 If shmmax and shmmall are too small, then:
 PostgreSQL requires some more shared memory to cache some tables, x
 Mb, do you want to increase your OS kernel parameters?
 Tweak shmmax and shmmall

CK Note that this still requires a kernel recompile on FreeBSD :(

According to whom?  sysctl is your friend.  Some sysctl settings may
require reboot, but I don't think the SHM ones do.


-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Vivek Khera, Ph.D.Khera Communications, Inc.
Internet: [EMAIL PROTECTED]   Rockville, MD   +1-240-453-8497
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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Christopher Browne
Centuries ago, Nostradamus foresaw when [EMAIL PROTECTED] (Vivek Khera) would write:
 JB == Josh Berkus [EMAIL PROTECTED] writes:

 JB Chris,
  PostgreSQL requires some more shared memory to cache some tables, x Mb,
  do you want to increase your OS kernel parameters?
 
 Tweak shmmax and shmmall
 
 Note that this still requires a kernel recompile on FreeBSD :(

 JB Not our fault, now is it?  This would mean that we wouldn't be
 JB able to script for FreeBSD.  Bug the FreeBSD developers.

 I read it on the net so it must be true applies here.  You /can/ set
 these values via sysctl calls.

Yes, indeed, sysctl can tweak these values fairly adequately.

Now, numbers of semaphors are not as readily tweaked; I wound up
limited, the other day, when I tried setting values for...

  kern.ipc.semmns
  kern.ipc.semmni
-- 
let name=cbbrowne and tld=ntlug.org in String.concat @ [name;tld];;
http://www.ntlug.org/~cbbrowne/x.html
So, when you typed in the date, it exploded into a sheet of blue
flame and burned the entire admin wing to the ground? Yes, that's a
known bug. We'll be fixing it in the next release. Until then, try not
to use European date format, and keep an extinguisher handy.
-- [EMAIL PROTECTED] (Tequila Rapide) 

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Tom Lane
Sean Chittenden [EMAIL PROTECTED] writes:
 Every few months one of the uber core BSD hackers threatens to rewrite
 that part of PG because high up in the BSD camp, it's common belief
 that shm* is a source of performance loss for PostgreSQL. 

They're full of it.  RAM is RAM, no?  Once you've got the memory mapped
into your address space, it's hard to believe that it matters how you
got hold of it.

In any case, mmap doesn't have the semantics we need.  See past
discussions.

regards, tom lane

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Christopher Kings-Lynne
If shmmax and shmmall are too small, then:
PostgreSQL requires some more shared memory to cache some tables, x
Mb, do you want to increase your OS kernel parameters?
Tweak shmmax and shmmall


CK Note that this still requires a kernel recompile on FreeBSD :(

According to whom?  sysctl is your friend.  Some sysctl settings may
require reboot, but I don't think the SHM ones do.
Hmmm...you may be right - I can't prove it now...

houston# sysctl -w kern.ipc.shmmax=999
kern.ipc.shmmax: 33554432 - 2147483647
Hrm.  Ok.  Maybe they've changed that in some recent version :)

Chris



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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-13 Thread Christopher Kings-Lynne

Yes, indeed, sysctl can tweak these values fairly adequately.

Now, numbers of semaphors are not as readily tweaked; I wound up
limited, the other day, when I tried setting values for...
  kern.ipc.semmns
  kern.ipc.semmni
Same.  Maybe that was the option I was thinking was read-only:

houston# sysctl kern.ipc.semmns
kern.ipc.semmns: 60
houston# sysctl -w kern.ipc.semmns=70
sysctl: oid 'kern.ipc.semmns' is read only
houston# sysctl kern.ipc.semmni
kern.ipc.semmni: 10
houston# sysctl -w kern.ipc.semmni=30
sysctl: oid 'kern.ipc.semmni' is read only
I like how they use oids :P

Chris



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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-12 Thread Josh Berkus
Nick,

 I reckon do a system scan first, and parse the current PostgreSQL conf
 file to figure out what the settings are. Also back it up with a date
 and time appended to the end to make sure there is a backup before
 overwriting the real conf file. Then a bunch of questions. What sort of
 questions would need to be asked and which parameters would these
 questions affect? So far, and from my limited understanding of the .conf
 file, I reckon there should be the following

Hmmm ... but I do think that there should be a file to store the user's 
previous answers.   That way, the script can easily be re-run to fix config 
issues.

 Here is your config of your hardware as detected. Is this correct ?

 This could potentially be several questions, i.e. one for proc, mem,
 os, hdd etc
 Would affect shared_buffers, sort_mem, effective_cache_size,
 random_page_cost

Actually, I think this would break down into:
-- Are Proc  Mem correct?  If not, type in correct values
-- Is OS correct? If not, select from list
-- Your HDD: is it:
1) IDE
2) Fast multi-disk SCSI or low-end RAID
3) Medium-to-high-end RAID

Other things, we don't care about.

 How was PostgreSQL compiled?

 This would be parameters such as the block size and a few other
 compile time parameters. If we can get to some of these read-only
 parameters than that would make this step easier, certainly for the new
 recruits amongst us.

Actually, from my perspective, we shouldn't bother with this; if an admin 
knows enough to set an alternate blaock size for PG, then they know enough to 
tweak the Conf file by hand.  I think we should just issue a warning that 
this script:
1) does not work for anyone who is using non-default block sizes, 
2) may not work well for anyone using unusual locales, optimization flags, or 
other non-default compile options except for language interfaces.
3) cannot produce good settings for embedded systems;
4) will not work well for systems which are extremely low on disk space, 
memory, or other resouces.
Basically, the script only really needs to work for the people who are 
installing PostgreSQL with the default options or from RPM on regular server 
or workstation machines with plenty of disk space for normal database 
purposes.  People who have more complicated setups can read the darned 
documentation and tune the conf file by hand.

 Is PostgreSQL the only thing being run on this computer?

First, becuase it affects a couple of other variables:

What kind of database server are you expecting to run?
A) Web Server (many small fast queries from many users, and not much update 
activity)
B) Online Transaction Processing (OLTP) database (many small updates 
constantly from many users; think accounting application).
C) Online Analytical Reporting (OLAP) database (a few large and complicated 
read-only queries aggregating large quantites of data for display)
D) Data Transformation tool (loading large amounts of data to process, 
transform, and output to other software)
E) Mixed-Use Database Server (a little of all of the above)
F) Workstation (installing this database on a user machine which also has a 
desktop, does word processing, etc.)

If the user answers anything but (F), then we ask:

Will you be running any other signficant software on this server, such as a 
web server, a Java runtime engine, or a reporting application? (yes|no)

If yes, then:

How much memory do you expect this other software, in total, to regularly use 
while PostgreSQL is in use?  (# in MB; should offer default of 50% of the RAM 
scanned).

 How are the clients going to connect?

 i.e. TCP or Unix sockets

We should warn them that they will still need to configure pg_hba.conf.

 How many clients can connect to this database at once?

 Affects max_connections

Should add a parenthetical comment that for applications which use pooled 
connections, or intermittent connection, such as Web applications, the number 
of concurrent connections is often much lower than the number of concurrent 
users.

 How many databases and how many tables in each database are going to be
 present?

 Affects max_fsm_pages, checkpoint_segments, checkpoint_timeout

Also need to ask if they have an idea of the total size of all databases, in 
MB or GB, which has a stronger relationship to those variables.

Also, this will give us a chance to check the free space on the PGDATA 
partition, and kick the user out with a warning if there is not at least 
2xExpected Size available.

 Do you want to vacuum you database regularly?

 Initial question for cron job

 It is recomended that you vacuum analyze every night, do you want to do
 this?
 It is also recomended that you vacuum full every month, do you want to
 do this?

Depends on size/type of database.  For large OLTP databases, I recommend 
vacuum as often as every 5 mintues, analyze every hour, and Vacuum Full + 
Reindex once a week.   For a workstation database, your 

Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-12 Thread Josh Berkus
Chris,

  PostgreSQL requires some more shared memory to cache some tables, x Mb,
  do you want to increase your OS kernel parameters?
 
 Tweak shmmax and shmmall

 Note that this still requires a kernel recompile on FreeBSD :(

Not our fault, now is it?   This would mean that we wouldn't be able to script 
for FreeBSD.   Bug the FreeBSD developers.

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-11 Thread Sean Chittenden
 NB shared_buffers = 1/16th of total memory
 NB effective_cache_size = 80% of the supposed kernel cache.
 
 I think Sean(?) mentioned this one for FreeBSD (Bash code):

sh, not bash.  :)

 echo effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))
 
 I've used it for my dedicated servers.  Is this calculation correct?

Yes, or it's real close at least.  vfs.hibufspace is the amount of
kernel space that's used for caching IO operations (minus the
necessary space taken for the kernel).  If you're real paranoid, you
could do some kernel profiling and figure out how much of the cache is
actually disk IO and multiply the above by some percentage, say 80%?
I haven't found it necessary to do so yet.  Since hibufspace is all IO
and caching any net activity is kinda pointless and I assume that 100%
of it is used for a disk cache and don't use a multiplier.  The 8192,
however, is the size of a PG page, so, if you tweak PG's page size,
you have to change this constant (*grumbles*).

-sc

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-11 Thread Ron Johnson
On Sat, 2003-10-11 at 05:22, Harald Fuchs wrote:
 In article [EMAIL PROTECTED],
 Rod Taylor [EMAIL PROTECTED] writes:
 
  Would anyone object to a patch that exports the blocksize via a
  readonly GUC?  Too many tunables are page dependant, which is
  infuriating when copying configs from DB to DB.  I wish pgsql had some
  notion of percentages for values that end with a '%'.
 
  Rather than showing the block size, how about we change the tunables to
  be physical sizes rather than block based?
 
  effective_cache_size = 1.5GB
  shared_buffers = 25MB
 
 Amen!  Being forced to set config values in some obscure units rather
 than bytes is an ugly braindamage which should be easy to fix.

But it's too user-friendly to do it this way!

-- 
-
Ron Johnson, Jr. [EMAIL PROTECTED]
Jefferson, LA USA

When Swedes start committing terrorism, I'll become suspicious of
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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-11 Thread Christopher Kings-Lynne

If shmmax and shmmall are too small, then:

PostgreSQL requires some more shared memory to cache some tables, x Mb, 
do you want to increase your OS kernel parameters?

   Tweak shmmax and shmmall
Note that this still requires a kernel recompile on FreeBSD :(

Chris

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Nick Barr
- Original Message -
From: Nick Barr [EMAIL PROTECTED]
To: [EMAIL PROTECTED]
Sent: Friday, October 10, 2003 1:35 PM
Subject: go for a script! / ex: PostgreSQL vs. MySQL


  I will also post it on me website and as I develop it further new
versions
 will appear there

 http://www.chuckie.co.uk/postgresql/pg_autoconfig.pl

Make that

http://www.chuckie.co.uk/postgresql/pg_autoconfig.txt


Nick





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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Josh Berkus
Nick,

 Having been following the thread on go for a script! / ex: PostgreSQL vs.
 MySQL. I thought I would throw something together in Perl. 

Cool!   Would you be willing to work with me so that I can inject some of my 
knowledge of .conf tuning?

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Vivek Khera
 SC == Sean Chittenden [EMAIL PROTECTED] writes:

SC patches to extract info from their OS so that initdb can make useful
SC decisions.  Or, lastly, does anyone think that this should be in a
SC different, external program?  -sc

Well, there should definitely be a way to run a get current best
tuning advice for those times when I go and do something like add a
Gig of RAM. ;-)

Also, I'm sure the tuning advice will change over time, so having to
do initdb to get that advice would be a bit onerous.

As long as initdb has an option for just getting the tuning info, I
see no reason to make it separate.

-- 
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Internet: [EMAIL PROTECTED]   Rockville, MD   +1-240-453-8497
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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Vivek Khera
 NB == Nick Barr [EMAIL PROTECTED] writes:

NB So far:

NB shared_buffers = 1/16th of total memory
NB effective_cache_size = 80% of the supposed kernel cache.

Please take into account the blocksize compiled into PG, too...


-- 
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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Josh Berkus
Vivek,

 NB shared_buffers = 1/16th of total memory
 NB effective_cache_size = 80% of the supposed kernel cache.

 Please take into account the blocksize compiled into PG, too...

We can;t change the blocksize in a script that only does the .conf file.  Or 
are you suggesting something else?

-- 
Josh Berkus
Aglio Database Solutions
San Francisco

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Vivek Khera
 JB == Josh Berkus [EMAIL PROTECTED] writes:

JB Vivek,
NB shared_buffers = 1/16th of total memory
NB effective_cache_size = 80% of the supposed kernel cache.
 
 Please take into account the blocksize compiled into PG, too...

JB We can;t change the blocksize in a script that only does the .conf
JB file.  Or are you suggesting something else?


when you compute optimal shared buffers and effective cache size,
these are in terms of blocksize.  so if I have 16k block size, you
can't compute based on default 8k blocksize.  at worst, it would have
to be a parameter you pass to the tuning script.

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Sean Chittenden
 NB So far:
 
 NB shared_buffers = 1/16th of total memory
 NB effective_cache_size = 80% of the supposed kernel cache.
 
 Please take into account the blocksize compiled into PG, too...

Would anyone object to a patch that exports the blocksize via a
readonly GUC?  Too many tunables are page dependant, which is
infuriating when copying configs from DB to DB.  I wish pgsql had some
notion of percentages for values that end with a '%'.  -sc

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Bruce Momjian
Sean Chittenden wrote:
  NB So far:
  
  NB shared_buffers = 1/16th of total memory
  NB effective_cache_size = 80% of the supposed kernel cache.
  
  Please take into account the blocksize compiled into PG, too...
 
 Would anyone object to a patch that exports the blocksize via a
 readonly GUC?  Too many tunables are page dependant, which is
 infuriating when copying configs from DB to DB.  I wish pgsql had some
 notion of percentages for values that end with a '%'.  -sc

Makes sense to me --- we already have some read-only GUC variables.

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Rod Taylor
On Fri, 2003-10-10 at 18:59, Sean Chittenden wrote:
  NB So far:
  
  NB shared_buffers = 1/16th of total memory
  NB effective_cache_size = 80% of the supposed kernel cache.
  
  Please take into account the blocksize compiled into PG, too...
 
 Would anyone object to a patch that exports the blocksize via a
 readonly GUC?  Too many tunables are page dependant, which is
 infuriating when copying configs from DB to DB.  I wish pgsql had some
 notion of percentages for values that end with a '%'.

Rather than showing the block size, how about we change the tunables to
be physical sizes rather than block based?

effective_cache_size = 1.5GB
shared_buffers = 25MB

Percentages would be slick as well, but doing the above should fix most
of the issue -- and be friendlier to read.


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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-10 Thread Christopher Kings-Lynne
NB shared_buffers = 1/16th of total memory
NB effective_cache_size = 80% of the supposed kernel cache.
I think Sean(?) mentioned this one for FreeBSD (Bash code):

echo effective_cache_size = $((`sysctl -n vfs.hibufspace` / 8192))

I've used it for my dedicated servers.  Is this calculation correct?

Chris

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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-09 Thread Paul Thomas
On 09/10/2003 09:29 Oliver Scheit wrote:
Hi guys,

I followed the discussion and here are my 0.2$:

I think instead of thinking about where to put the
information about tuning, someone should provide a
pgsql-autotune. Maybe even a shell script would do the
trick.
It's not so hard to find out, how much memory is installed,
and IMHO SHARED_BUFFERS, SORT_MEM and EFFECTIVE_CACHE_SIZE
depend heavily on this. a cat /proc/sys/kernel/shmmax
would give some valuable information on linux boxes,
there is probably other stuff for different OSes.
random_page_cost could be set after probing the harddisks,
maybe even do a hdparm -tT if they seem to be ATA, not SCSI.
Now, let's pretend the script finds out there is 1 GB RAM,
it could ask something like Do you want to optimize the
settings for postgres (other applications may suffer from
having not enough RAM) or do you want to use moderate
settings?
Something like this, you get the idea.


ISR reading that 7.4 will use a default of shared_beffers = 1000 if the 
machine can support it (most can). This alone should make a big difference 
in out-of-the-box performance.

--
Paul Thomas
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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-09 Thread Dror Matalon

Yeah, I had similar thought to Oliver's and suspected that this would be
the answer. 
Also, while it's not too hard to do this for a single platform, it gets
complecated once you start looking at different ones.

Josh, let me know when you're ready to do this. I'll try to help,
although my perl's kind of rusty. Also, can you even assume perl for a
postgres install? Does Solaris, for instance come with perl?

Dror

On Thu, Oct 09, 2003 at 09:56:11AM -0700, Josh Berkus wrote:
 Oliver,
 
  I think instead of thinking about where to put the
  information about tuning, someone should provide a
  pgsql-autotune. Maybe even a shell script would do the
  trick.
 
 Well, you see, there's the issue.  I think someone.  Lots of people have 
 spoken in favor of an auto-conf script; nobody so far has stepped forward 
 to get it done for 7.4, and I doubt we have time now.
 
 I'll probably create a Perl script in a month or so, but not before that 
 
 -- 
 Josh Berkus
 Aglio Database Solutions
 San Francisco
 
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Re: [PERFORM] go for a script! / ex: PostgreSQL vs. MySQL

2003-10-09 Thread Sean Chittenden
 Yeah, I had similar thought to Oliver's and suspected that this
 would be the answer.  Also, while it's not too hard to do this for a
 single platform, it gets complecated once you start looking at
 different ones.
 
 Josh, let me know when you're ready to do this. I'll try to help,
 although my perl's kind of rusty. Also, can you even assume perl for
 a postgres install? Does Solaris, for instance come with perl?

Um, why not wait until the C version of initdb is committed, then
steak out a section that'll allow us to submit patches to have initdb
autotune to our hearts content?  There's a tad bit of precedence with
having shared buffer's automatically set in initdb, why not continue
with it?  I know under FreeBSD initdb will have some #ifdef's to wrap
around the syscall sysctl() to get info about kernel bits.  Talking
about how to expand handle this gracefully for a gazillion different
platforms might be a more useful discussion at this point because I'm
sure people from their native OS will be able to contrib the necessary
patches to extract info from their OS so that initdb can make useful
decisions.  Or, lastly, does anyone think that this should be in a
different, external program?  -sc

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