Maxlen exceed 25
A user worried that 'onstat -g ioq' showed maxlen values of 32-64 on his kio queues, far above the commonly quoted guideline of 25. Respondents (Mark Stock, Madison Pruet) explained the 25 rule applies to AIO virtual processors, not KAIO: with kernel AIO the OS handles the non-blocking requests, so long queues are harmless provided you have roughly one CPU VP per physical processor. A second poster with large gfd queue lengths on 7.30 (no KAIO) was told her case differs and needs a full tuning cycle - add AIO VPs or switch to KAIO - with the real focus on reducing total I/Os per second rather than queue length. No single definitive fix is recorded for the second case.
Auto-generated by DrWatson from the posts below — may be imperfect; read the full thread.
Hi all,
I use the onstat -g ioq and have the following information
AIO I/O queues:
q name/id len maxlen totalops dskread dskwrite dskcopy
kio 0 0 64 245740605 243860239 1880366 0
kio 1 0 64 225398151 223644673 1753478 0
kio 2 0 39 153270901 151775269 1495632 0
kio 3 0 62 108240810 106971733 1269077 0
kio 4 0 33 16292989 15771773 521216 0
kio 5 0 64 74956527 73902907 1053620 0
kio 6 0 32 20469740 19905662 564078 0
kio 7 0 32 52528564 51648496 880068 0
kio 8 0 35 37053372 36308162 745210 0
kio 9 0 61 27060908 26398981 661927 0
kio 10 0 33 13736374 13249805 486569 0
kio 11 0 32 12006058 11535554 470504 0
adt 0 0 0 0 0 0 0
From most doc, it is recommand that maxlen should not exceed 25. So what
should i do now?? Could anyone give me more suggestion please
Franklin
FRANKLIN
TANG wrote:
> Hi all,
> I use the onstat -g ioq and have the following information
> AIO I/O queues:
> q name/id len maxlen totalops dskread dskwrite dskcopy
> kio 0 0 64 245740605 243860239 1880366 0
> kio 1 0 64 225398151 223644673 1753478 0
> kio 2 0 39 153270901 151775269 1495632 0
> kio 3 0 62 108240810 106971733 1269077 0
> kio 4 0 33 16292989 15771773 521216 0
> kio 5 0 64 74956527 73902907 1053620 0
> kio 6 0 32 20469740 19905662 564078 0
> kio 7 0 32 52528564 51648496 880068 0
> kio 8 0 35 37053372 36308162 745210 0
> kio 9 0 61 27060908 26398981 661927 0
> kio 10 0 33 13736374 13249805 486569 0
> kio 11 0 32 12006058 11535554 470504 0
> adt 0 0 0 0 0 0 0
>
>>From most doc, it is recommand that maxlen should not exceed 25. So what
should i do now?? Could anyone give me more suggestion please
That recommendation is for AIO, not KAIO. The queues for KIO can be
quite large without affecting performance because the OS is handling the
requests much faster than with AIO.
As long as you have at least 12 physical CPUs in your box, as you seem
to have 12 CPU VPs configured.
Cheers,
--
Mark.
+----------------------------------------------------------+-----------+
| Mark D. Stock mailto:mdstock@MydasSolutions.com |//////// /|
| Mydas Solutions Ltd http://MydasSolutions.com |///// / //|
| +-----------------------------------+//// / ///|
| |We value your comments, which have |/// / ////|
| |been recorded and automatically |// / /////|
| |emailed back to us for our records.|/ ////////|
+----------------------+-----------------------------------+-----------+
I think that the 25 limit is the suggestion for using aiovps, not kaio.
"FRANKLIN TANG"
<franklin@macausl To: ids@iiug.org
ot.com> cc:
Sent by: Subject: Maxlen exceed 25 [306]
forum.subscriber@
iiug.org
02/10/2003 01:16
AM
Hi all,
I use the onstat -g ioq and have the following information
AIO I/O queues:
q name/id len maxlen totalops dskread dskwrite dskcopy
kio 0 0 64 245740605 243860239 1880366 0
kio 1 0 64 225398151 223644673 1753478 0
kio 2 0 39 153270901 151775269 1495632 0
kio 3 0 62 108240810 106971733 1269077 0
kio 4 0 33 16292989 15771773 521216 0
kio 5 0 64 74956527 73902907 1053620 0
kio 6 0 32 20469740 19905662 564078 0
kio 7 0 32 52528564 51648496 880068 0
kio 8 0 35 37053372 36308162 745210 0
kio 9 0 61 27060908 26398981 661927 0
kio 10 0 33 13736374 13249805 486569 0
kio 11 0 32 12006058 11535554 470504 0
adt 0 0 0 0 0 0 0
From most doc, it is recommand that maxlen should not exceed 25. So what
should i do now?? Could anyone give me more suggestion please
Franklin
Hi,
I was going to ask the same question, because we have
much bigger numbers in the maxlens column:
informix@vaprp1> onstat -g ioq|more
Informix Dynamic Server Version 7.30.UC10 -- On-Line
-- Up 3 days 21:30:25 --
575576 Kbytes
AIO I/O queues:
q name/id len maxlen totalops dskread dskwrite
dskcopy
adt 0 0 0 0 0 0
0
msc 0 0 1 347132 0 0
0
aio 0 0 16 341508 254473 2
0
pio 0 0 1 47653 0 47653
0
lio 0 0 1 920669 0 920669
0
gfd 3 0 19 16773 4907 11866
0
gfd 4 0 1 165592 165592 0
0
gfd 5 0 174 406608 123179 283429
0
gfd 6 0 233 2214357 1998582 215775
0
gfd 7 0 1428 1892334 1711859 180475
0
gfd 8 0 884 1819782 1643994 175788
0
gfd 9 0 405 1719912 1594551 125361
0
gfd 10 0 723 2251513 1954953 296560
0
gfd 11 0 157 565028 430392 134636
0
What would you recommend in our case?
Thanks,
Milena
--- Madison Pruet <mpruet@us.ibm.com> wrote:
>
>
>
>
> I think that the 25 limit is the suggestion for
> using aiovps, not kaio.
>
>
>
>
>
>
>
>
> "FRANKLIN TANG"
>
>
> <franklin@macausl To:
> ids@iiug.org
>
> ot.com> cc:
>
>
> Sent by:
> Subject: Maxlen exceed 25 [306]
>
> forum.subscriber@
>
>
> iiug.org
>
>
>
>
>
>
>
>
> 02/10/2003 01:16
>
>
> AM
>
>
>
>
>
>
>
>
>
>
>
>
> Hi all,
> I use the onstat -g ioq and have the following
> information
> AIO I/O queues:
> q name/id len maxlen totalops dskread dskwrite
> dskcopy
> kio 0 0 64 245740605 243860239 1880366
> 0
> kio 1 0 64 225398151 223644673 1753478
> 0
> kio 2 0 39 153270901 151775269 1495632
> 0
> kio 3 0 62 108240810 106971733 1269077
> 0
> kio 4 0 33 16292989 15771773 521216
> 0
> kio 5 0 64 74956527 73902907 1053620
> 0
> kio 6 0 32 20469740 19905662 564078
> 0
> kio 7 0 32 52528564 51648496 880068
> 0
> kio 8 0 35 37053372 36308162 745210
> 0
> kio 9 0 61 27060908 26398981 661927
> 0
> kio 10 0 33 13736374 13249805 486569
> 0
> kio 11 0 32 12006058 11535554 470504
> 0
> adt 0 0 0 0 0 0
> 0
>
> From most doc, it is recommand that maxlen should
> not exceed 25. So what
> should i do now?? Could anyone give me more
> suggestion please
>
> Franklin
>
>
>
>
>
__________________________________________________
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Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
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Our
database is sitting on a NetApp, therefore I don't
think fragmentation is going to make any difference.
May be adding more AIO VPS will help. Is there any
rule of how many AIO VPs should I add. I know the rule
that Informix recommends is 1 AIO VP per chunk. But we
have already 18 AIO VPs for 9 chunks, which makes 2
AIO VPs per chunk.
Sorry, but what "counts" should I check from "onstat
-g ath"?Thanks,
Milena
--- Jack Parker <vze2qjg5@verizon.net> wrote:
> Add more AIOvps or fragment your data across more
> disks.
>
> onstat -g ath | grep aio to check count
> onmode -p +<n> aio to add (while online - otherwise
> edit $ONCONFIG)>
> Your chunks 5, 6 and 8 are fairly hot, you could
> spread the load off of
> them.
>
> Let me guess, chunk 1 is rootdbs, chunk2 is log?
> Those are barely working
> up a sweat - BUT then all of this is in terms of
> logical disk, there may be
> something else going on underneath the covers.
>
> cheers
> j.
>
> (default .sig)
> If my note seems hurried, short, cross or (in the
> words of one young lady)
> 'hard-*ssed' it's probably because I am working with
> this cr*ppy mail
> program and have left my glasses downstairs
> somewhere and can't see what I'm
> typing - please don't take it personally. I
> probably didn't or couldn't
> read the entire email you sent.
> ----- Original Message -----
> From: "Milena Ilieva " <milena_ilieva@yahoo.com>
> To: <ids@iiug.org>
> Sent: Monday, February 10, 2003 1:40 PM
> Subject: Re: Maxlen exceed 25 [318]
>
>
> > Hi,
> >
> > I was going to ask the same question, because we
> have
> > much bigger numbers in the maxlens column:
> >
> > informix@vaprp1> onstat -g ioq|more
> >
> > Informix Dynamic Server Version 7.30.UC10 --
> On-Line
> > -- Up 3 days 21:30:25 --
> > 575576 Kbytes
> >
> > AIO I/O queues:
> > q name/id len maxlen totalops dskread dskwrite
> > dskcopy
> > adt 0 0 0 0 0 0
> > 0
> > msc 0 0 1 347132 0 0
> > 0
> > aio 0 0 16 341508 254473 2
> > 0
> > pio 0 0 1 47653 0 47653
> > 0
> > lio 0 0 1 920669 0 920669
> > 0
> > gfd 3 0 19 16773 4907 11866
> > 0
> > gfd 4 0 1 165592 165592 0
> > 0
> > gfd 5 0 174 406608 123179 283429
> > 0
> > gfd 6 0 233 2214357 1998582 215775
> > 0
> > gfd 7 0 1428 1892334 1711859 180475
> > 0
> > gfd 8 0 884 1819782 1643994 175788
> > 0
> > gfd 9 0 405 1719912 1594551 125361
> > 0
> > gfd 10 0 723 2251513 1954953 296560
> > 0
> > gfd 11 0 157 565028 430392 134636
> > 0
> >
> > What would you recommend in our case?
> >
> > Thanks,
> >
> > Milena
> > --- Madison Pruet <mpruet@us.ibm.com> wrote:
> > >
> > >
> > >
> > >
> > > I think that the 25 limit is the suggestion for
> > > using aiovps, not kaio.
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > "FRANKLIN TANG"
> > >
> > >
> > > <franklin@macausl
> To:
> > > ids@iiug.org
> > >
> > > ot.com>
> cc:
> > >
> > >
> > > Sent by:
> > > Subject: Maxlen exceed 25 [306]
> > >
> > > forum.subscriber@
> > >
> > >
> > > iiug.org
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > 02/10/2003 01:16
> > >
> > >
> > > AM
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Hi all,
> > > I use the onstat -g ioq and have the following
> > > information
> > > AIO I/O queues:
> > > q name/id len maxlen totalops dskread
> dskwrite
> > > dskcopy
> > > kio 0 0 64 245740605 243860239
> 1880366
> > > 0
> > > kio 1 0 64 225398151 223644673
> 1753478
> > > 0
> > > kio 2 0 39 153270901 151775269
> 1495632
> > > 0
> > > kio 3 0 62 108240810 106971733
> 1269077
> > > 0
> > > kio 4 0 33 16292989 15771773
> 521216
> > > 0
> > > kio 5 0 64 74956527 73902907
> 1053620
> > > 0
> > > kio 6 0 32 20469740 19905662
> 564078
> > > 0
> > > kio 7 0 32 52528564 51648496
> 880068
> > > 0
> > > kio 8 0 35 37053372 36308162
> 745210
> > > 0
> > > kio 9 0 61 27060908 26398981
> 661927
> > > 0
> > > kio 10 0 33 13736374 13249805
> 486569
> > > 0
> > > kio 11 0 32 12006058 11535554
> 470504
> > > 0
> > > adt 0 0 0 0 0
> 0
> > > 0
> > >
> > > From most doc, it is recommand that maxlen
> should
> > > not exceed 25. So what
> > > should i do now?? Could anyone give me more
> > > suggestion please
> > >
> > > Franklin
> > >
> > >
> > >
>
=== message truncated ===
__________________________________________________
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Yahoo! Mail Plus - Powerful. Affordable. Sign up now.
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KAIO is a form of async IO. Adding additional AIOVPS won't help as the
bulk of the work is being done by the OS.
Since KAIO is async IO, then assuming that you have one cpuVP per physical
processor, you will not improve performance by attempting to do more.
Also, since KAIO is async IO, then the size of the queue is not all that
improtant because it is non-blocking IO.
However, that is probably not the key issue. Instead the focus needs to be
on "What can I do to decrease the total number of IO/sec". Not "What can
I do to decrease the length of the IO queue".
M.Pruet
"Milena Ilieva "
<milena_ilieva@ya To: ids@iiug.org
hoo.com> cc:
Sent by: Subject: Re: Maxlen exceed 25 [321]
forum.subscriber@
iiug.org
02/10/2003 04:10
PM
Our database is sitting on a NetApp, therefore I don't
think fragmentation is going to make any difference.
May be adding more AIO VPS will help. Is there any
rule of how many AIO VPs should I add. I know the rule
that Informix recommends is 1 AIO VP per chunk. But we
have already 18 AIO VPs for 9 chunks, which makes 2
AIO VPs per chunk.
Sorry, but what "counts" should I check from "onstat
-g ath"?Thanks,
Milena
--- Jack Parker <vze2qjg5@verizon.net> wrote:
> Add more AIOvps or fragment your data across more
> disks.
>
> onstat -g ath | grep aio to check count
> onmode -p +<n> aio to add (while online - otherwise
> edit $ONCONFIG)>
> Your chunks 5, 6 and 8 are fairly hot, you could
> spread the load off of
> them.
>
> Let me guess, chunk 1 is rootdbs, chunk2 is log?
> Those are barely working
> up a sweat - BUT then all of this is in terms of
> logical disk, there may be
> something else going on underneath the covers.
>
> cheers
> j.
>
> (default .sig)
> If my note seems hurried, short, cross or (in the
> words of one young lady)
> 'hard-*ssed' it's probably because I am working with
> this cr*ppy mail
> program and have left my glasses downstairs
> somewhere and can't see what I'm
> typing - please don't take it personally. I
> probably didn't or couldn't
> read the entire email you sent.
> ----- Original Message -----
> From: "Milena Ilieva " <milena_ilieva@yahoo.com>
> To: <ids@iiug.org>
> Sent: Monday, February 10, 2003 1:40 PM
> Subject: Re: Maxlen exceed 25 [318]
>
>
> > Hi,
> >
> > I was going to ask the same question, because we
> have
> > much bigger numbers in the maxlens column:
> >
> > informix@vaprp1> onstat -g ioq|more
> >
> > Informix Dynamic Server Version 7.30.UC10 --
> On-Line
> > -- Up 3 days 21:30:25 --
> > 575576 Kbytes
> >
> > AIO I/O queues:
> > q name/id len maxlen totalops dskread dskwrite
> > dskcopy
> > adt 0 0 0 0 0 0
> > 0
> > msc 0 0 1 347132 0 0
> > 0
> > aio 0 0 16 341508 254473 2
> > 0
> > pio 0 0 1 47653 0 47653
> > 0
> > lio 0 0 1 920669 0 920669
> > 0
> > gfd 3 0 19 16773 4907 11866
> > 0
> > gfd 4 0 1 165592 165592 0
> > 0
> > gfd 5 0 174 406608 123179 283429
> > 0
> > gfd 6 0 233 2214357 1998582 215775
> > 0
> > gfd 7 0 1428 1892334 1711859 180475
> > 0
> > gfd 8 0 884 1819782 1643994 175788
> > 0
> > gfd 9 0 405 1719912 1594551 125361
> > 0
> > gfd 10 0 723 2251513 1954953 296560
> > 0
> > gfd 11 0 157 565028 430392 134636
> > 0
> >
> > What would you recommend in our case?
> >
> > Thanks,
> >
> > Milena
> > --- Madison Pruet <mpruet@us.ibm.com> wrote:
> > >
> > >
> > >
> > >
> > > I think that the 25 limit is the suggestion for
> > > using aiovps, not kaio.
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > "FRANKLIN TANG"
> > >
> > >
> > > <franklin@macausl
> To:
> > > ids@iiug.org
> > >
> > > ot.com>
> cc:
> > >
> > >
> > > Sent by:
> > > Subject: Maxlen exceed 25 [306]
> > >
> > > forum.subscriber@
> > >
> > >
> > > iiug.org
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > 02/10/2003 01:16
> > >
> > >
> > > AM
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > Hi all,
> > > I use the onstat -g ioq and have the following
> > > information
> > > AIO I/O queues:
> > > q name/id len maxlen totalops dskread
> dskwrite
> > > dskcopy
> > > kio 0 0 64 245740605 243860239
> 1880366
> > > 0
> > > kio 1 0 64 225398151 223644673
> 1753478
> > > 0
> > > kio 2 0 39 153270901 151775269
> 1495632
> > > 0
> > > kio 3 0 62 108240810 106971733
> 1269077
> > > 0
> > > kio 4 0 33 16292989 15771773
> 521216
> > > 0
> > > kio 5 0 64 74956527 73902907
> 1053620
> > > 0
> > > kio 6 0 32 20469740 19905662
> 564078
> > > 0
> > > kio 7 0 32 52528564 51648496
> 880068
> > > 0
> > > kio 8 0 35 37053372 36308162
> 745210
> > > 0
> > > kio 9 0 61 27060908 26398981
> 661927
> > > 0
> > > kio 10 0 33 13736374 13249805
> 486569
> > > 0
> > > kio 11 0 32 12006058 11535554
> 470504
> > > 0
> > > adt 0 0 0 0 0
> 0
> > > 0
> > >
> > > From most doc, it is recommand that maxlen
> should
> > > not exceed 25. So what
> > > should i do now?? Could anyone give me more
> > > suggestion please
> > >
> > > Franklin
> > >
> > >
> > >
>
=== message truncated ===
__________________________________________________
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Milena
Ilieva wrote:
> Hi,
>
> I was going to ask the same question, because we have
> much bigger numbers in the maxlens column:
>
> informix@vaprp1> onstat -g ioq|more
>
> Informix Dynamic Server Version 7.30.UC10 -- On-Line
> -- Up 3 days 21:30:25 --
> 575576 Kbytes
>
> AIO I/O queues:
> q name/id len maxlen totalops dskread dskwrite
> dskcopy
> adt 0 0 0 0 0 0
> 0
> msc 0 0 1 347132 0 0
> 0
> aio 0 0 16 341508 254473 2
> 0
> pio 0 0 1 47653 0 47653
> 0
> lio 0 0 1 920669 0 920669
> 0
> gfd 3 0 19 16773 4907 11866
> 0
> gfd 4 0 1 165592 165592 0
> 0
> gfd 5 0 174 406608 123179 283429
> 0
> gfd 6 0 233 2214357 1998582 215775
> 0
> gfd 7 0 1428 1892334 1711859 180475
> 0
> gfd 8 0 884 1819782 1643994 175788
> 0
> gfd 9 0 405 1719912 1594551 125361
> 0
> gfd 10 0 723 2251513 1954953 296560
> 0
> gfd 11 0 157 565028 430392 134636
> 0
>
> What would you recommend in our case?
Well your case is totally different.
Start using Kernel AIO? Allocate more AIO VPs?
There's a whole tuning cycle to go through if you are having performance
issues with those queues.
Cheers,
--
Mark.
+----------------------------------------------------------+-----------+
| Mark D. Stock mailto:mdstock@MydasSolutions.com |//////// /|
| Mydas Solutions Ltd http://MydasSolutions.com |///// / //|
| +-----------------------------------+//// / ///|
| |We value your comments, which have |/// / ////|
| |been recorded and automatically |// / /////|
| |emailed back to us for our records.|/ ////////|
+----------------------+-----------------------------------+-----------+
Madison Pruet wrote: > KAIO is a form of async IO. Adding additional AIOVPS won't help as the > bulk of the work is being done by the OS. I think Jack was replying to Milena Ilieva, who is not using KAIO, not the original poster Franklin Tang, who is. x-) But I could be wrong. You see this is what happens when you have a list that doesn't support threading! :-| > Since KAIO is async IO, then assuming that you have one cpuVP per physical > processor, you will not improve performance by attempting to do more. > Also, since KAIO is async IO, then the size of the queue is not all that > improtant because it is non-blocking IO. Which is good advice for Franklin. > However, that is probably not the key issue. Instead the focus needs to be > on "What can I do to decrease the total number of IO/sec". Not "What can > I do to decrease the length of the IO queue". Which is probably good advice for both Milena & Franklin! As Jack & I said, there is a whole tuning cycle to go through. Cheers, -- Mark. +----------------------------------------------------------+-----------+ | Mark D. Stock mailto:mdstock@MydasSolutions.com |//////// /| | Mydas Solutions Ltd http://MydasSolutions.com |///// / //| | +-----------------------------------+//// / ///| | |We value your comments, which have |/// / ////| | |been recorded and automatically |// / /////| | |emailed back to us for our records.|/ ////////| +----------------------+-----------------------------------+-----------+
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