Re: AIO and Buffer Waits
OK your bufwaits ratio is less than one, and given the BTR also, you are
correct you need more buffers. Note that on a system with lots of inserts
over selects, the BTR's tend to be higher, but 48/hr is high even so. As
you, and Lester, note BTR should be single digits per hour and an ideal for
a typical OLTP system is aroung 6.0, but every system is different. Once
you get the performance problem licked, keep track so you know what's normal
for your system.
Art
Art S. Kagel
Advanced DataTools (www.advancedatatools.com)
Blog: http://informix-myview.blogspot.com/
Disclaimer: Please keep in mind that my own opinions are my own opinions and
do not reflect on my employer, Advanced DataTools, the IIUG, nor any other
organization with which I am associated either explicitly, implicitly, or by
inference. Neither do those opinions reflect those of other individuals
affiliated with any entity with which I am affiliated nor those of the
entities themselves.
On Wed, Jul 13, 2011 at 8:29 AM, Habichtsberg, Reinhard <
RHabichtsberg@arz-emmendingen.de> wrote:
> Hi Art,****
>
> ** **
>
> BTR is 48,57 per hour. According to Lester Knutsen should be < 6 per hour.
> ****
>
> ** **
>
> BUFFERPOOL looks like that and AUTO:LRU_TUNING is turn on:****
>
> ** **
>
> BUFFERPOOL
> size=2K,buffers=2400000,lrus=60,lru_min_dirty=0.200000,lru_max_dirty=0.400000
> ****>
> AUTO_LRU_TUNING 1****
>
> ** **
>
> onstat –p (last onstat –z 14 hours ago)****
>
> ** **
>
> IBM Informix Dynamic Server Version 11.50.FC7W3 -- On-Line -- Up 54 days
> 01:54:20 -- 8984576 Kbytes****
>
> ** **
>
> Profile****>
> dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits
> %cached****
>
> 142604256 1410570080 59284431722 99.76 61872253 98433717 227436232
> 72.80****
>
> ** **
>
> isamtot open start read write rewrite
> delete commit rollbk****
>
> 52046254582 216281491 457585123 48750470513 17730429 30711047
> 19268677 18995943 1446067****
>
> ** **
>
> gp_read gp_write gp_rewrt gp_del gp_alloc gp_free gp_curs*
> ***
>
> 14 0 9 0 0 0 0****
>
> ** **
>
> ovlock ovuserthread ovbuff usercpu syscpu numckpts flushes***
> *
>
> 0 0 0 317120.96 38441.46 134 163****
>
> ** **
>
> bufwaits lokwaits lockreqs deadlks dltouts ckpwaits
> compress seqscans****
>
> 20157325 126775 1927754927 0 0 5149
> 6933881 1205132****
>
> ** **
>
> ixda-RA idx-RA da-RA RA-pgsused lchwaits****
>
> 66150442 1636318 30850997 97300297 20233621****
>
> ** **
>
> What would be a reasonable value for lrus?****
>
> ** **
>
> TIA, Reinhard.****
>
> ** **
>
> *From:* Art Kagel [mailto:art.kagel@gmail.com]
> *Sent:* Wednesday, July 13, 2011 12:24 PM
> *To:* Habichtsberg, Reinhard
> *Cc:* informix-list@iiug.org
> *Subject:* Re: AIO and Buffer Waits****
>
> ** **
>
> Most bufwaits are caused by contention for the LRU queues, so increase the
> LRU queues for your buffer caches to maximum first. Use the BTR calculation
> and observing activity in onstat -P over time to determine if you may also
> need more buffers.
>
> Art
>
> Art S. Kagel
> Advanced DataTools (www.advancedatatools.com)
> Blog: http://informix-myview.blogspot.com/
>
> Disclaimer: Please keep in mind that my own opinions are my own opinions
> and do not reflect on my employer, Advanced DataTools, the IIUG, nor any
> other organization with which I am associated either explicitly, implicitly,
> or by inference. Neither do those opinions reflect those of other
> individuals affiliated with any entity with which I am affiliated nor those
> of the entities themselves.
>
>
> ****
>
> On Wed, Jul 13, 2011 at 2:49 AM, Habichtsberg, Reinhard <
> RHabichtsberg@arz-emmendingen.de> wrote:****
>
> We see the following waitstates on one of our Informix 11.50FC7W3 servers.
> He is running OLTP but also Decision Support.****
>
> ****
>
> (sum) 81125424549,00****
>
> reason aio****
>
> ****
>
> (sum) 62105207794,00****
>
> reason buffer****
>
> ****
>
> (sum) 61713678094,10****
>
> reason mt yield n****
>
> ****
>
> (sum) 61561288458,60****
>
> reason mt yield****
>
> ****
>
> (sum) 29339327941,19****
>
> reason mt ready****
>
> ****
>
> (sum) 15649570039,20****
>
> reason running****
>
> ****
>
> (sum) 3340893922,100****
>
> reason log i/o****
>
> ****
>
> (sum) 1550362515,000****
>
> reason mt yield 0****
>
> ****
>
> (sum) 1439244418,300****
>
> reason checkpoint****
>
> ****
>
> (sum) 162272243,0000****
>
> reason lock****
>
> ****
>
> (sum) 157356745,3000****
>
> reason mutex****
>
> ****
>
> (sum) 21639138,60000****
>
> reason full Q****
>
> ****
>
> What do you suggest to reduce IO and Bufferwaits. My idea is to increase
> the buffers.****
>
> ****
>
> TIA,****
>
> Reinhard.****
>
>
> _______________________________________________
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>
> ** **
>
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