I/O Blocking

I/O Blocking

[Jason C. Leach]

Hi,

Both the RAID (Promise SuperTrak 6000) or the USB subsystems really 
drive the system load up. I'm using a AMD 3200+ system that is only a 
few months old with the 2.4.25 kernel.  When the I/O systems are 
blocking the system is very unresponsive. Some times samba will timeout, 
or I'll wait several seconds for commands like df, top, w and so on.

I am wondering if I were to use a dual CPU system, would this solve my 
I/O blocking problem?  Would one CPU tend to the I/O subsystem and the 
second would deal with other system requests I (samba, DB, LDAP, ...)?

RE: I/O Blocking

[Guy]

What is the CPU load like?  Are you at 100%?  If so a second CPU may help.
If you are blocked on i/o it should not use much CPU, so my guess is your
CPU load is very low, and a second CPU won't do much.  How much RAM do you
have?  Are you swapping?

Guy

-----Original Message-----
From: linux-raid-owner@vger.kernel.org
[mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Jason C. Leach
Sent: Thursday, July 22, 2004 12:29 PM
To: linux-raid@vger.kernel.org
Subject: I/O Blocking

Hi,

Both the RAID (Promise SuperTrak 6000) or the USB subsystems really 
drive the system load up. I'm using a AMD 3200+ system that is only a 
few months old with the 2.4.25 kernel.  When the I/O systems are 
blocking the system is very unresponsive. Some times samba will timeout, 
or I'll wait several seconds for commands like df, top, w and so on.

I am wondering if I were to use a dual CPU system, would this solve my 
I/O blocking problem?  Would one CPU tend to the I/O subsystem and the 
second would deal with other system requests I (samba, DB, LDAP, ...)?
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Re: I/O Blocking

[Jason C. Leach]

Guy:

CPU load is very low (95-96% idle), load avg is 2. The system has 512MB 
RAM, some free and only a few megs swapped out.  If I was really working 
the RAID card I would get load avgs more like 2.5-3.  Right now just 
light USB and system usage and I am at 2.

I though if one CPU was tied up with the process that is blocking (using 
the RAID card), then the second would be free to deal with user 
requests. Or am I misunderstanding SMP and blocking I/O?

J.

Guy wrote:

>What is the CPU load like?  Are you at 100%?  If so a second CPU may help.
>If you are blocked on i/o it should not use much CPU, so my guess is your
>CPU load is very low, and a second CPU won't do much.  How much RAM do you
>have?  Are you swapping?
>
>Guy
>
>-----Original Message-----
>From: linux-raid-owner@vger.kernel.org
>[mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Jason C. Leach
>Sent: Thursday, July 22, 2004 12:29 PM
>To: linux-raid@vger.kernel.org
>Subject: I/O Blocking
>
>Hi,
>
>Both the RAID (Promise SuperTrak 6000) or the USB subsystems really 
>drive the system load up. I'm using a AMD 3200+ system that is only a 
>few months old with the 2.4.25 kernel.  When the I/O systems are 
>blocking the system is very unresponsive. Some times samba will timeout, 
>or I'll wait several seconds for commands like df, top, w and so on.
>
>I am wondering if I were to use a dual CPU system, would this solve my 
>I/O blocking problem?  Would one CPU tend to the I/O subsystem and the 
>second would deal with other system requests I (samba, DB, LDAP, ...)?
>-
>To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>  
>

RE: I/O Blocking

[Guy]

If your 1 CPU is 95% idle, it can do other "user requests".  But not if the
other "user requests" require disk I/O, they will also block regardless of
which CPU they are using.  I think there is a performance problem with your
disks.  But just a guess.

Guy

-----Original Message-----
From: linux-raid-owner@vger.kernel.org
[mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Jason C. Leach
Sent: Thursday, July 22, 2004 2:10 PM
To: Guy
Cc: linux-raid@vger.kernel.org
Subject: Re: I/O Blocking

Guy:

CPU load is very low (95-96% idle), load avg is 2. The system has 512MB 
RAM, some free and only a few megs swapped out.  If I was really working 
the RAID card I would get load avgs more like 2.5-3.  Right now just 
light USB and system usage and I am at 2.

I though if one CPU was tied up with the process that is blocking (using 
the RAID card), then the second would be free to deal with user 
requests. Or am I misunderstanding SMP and blocking I/O?

J.

Guy wrote:

>What is the CPU load like?  Are you at 100%?  If so a second CPU may help.
>If you are blocked on i/o it should not use much CPU, so my guess is your
>CPU load is very low, and a second CPU won't do much.  How much RAM do you
>have?  Are you swapping?
>
>Guy
>
>-----Original Message-----
>From: linux-raid-owner@vger.kernel.org
>[mailto:linux-raid-owner@vger.kernel.org] On Behalf Of Jason C. Leach
>Sent: Thursday, July 22, 2004 12:29 PM
>To: linux-raid@vger.kernel.org
>Subject: I/O Blocking
>
>Hi,
>
>Both the RAID (Promise SuperTrak 6000) or the USB subsystems really 
>drive the system load up. I'm using a AMD 3200+ system that is only a 
>few months old with the 2.4.25 kernel.  When the I/O systems are 
>blocking the system is very unresponsive. Some times samba will timeout, 
>or I'll wait several seconds for commands like df, top, w and so on.
>
>I am wondering if I were to use a dual CPU system, would this solve my 
>I/O blocking problem?  Would one CPU tend to the I/O subsystem and the 
>second would deal with other system requests I (samba, DB, LDAP, ...)?
>-
>To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>  
>

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Re: I/O Blocking

[Kanoa Withington]

Jason,

There is a technical answer to your question which I cannot properly
relate to you. The practical answer is yes, an SMP system will
generally perform better under heavy interrupt conditions and would
probably help with the situation you are having.

That said, the problem you are having is not lack of CPU
performance. I don't know what it is but you need to look into it
before throwing another mega-cpu at it. You might have too many I/O
devices sharing the same IRQ, it could be something weird like a
haywire parallel port device. Take a careful look at how your
equipment is set up and do some experiments turning things off and on,
etc. You can probably get to the bottom of it without upgrading
anything.

-Kanoa

On Thu, 22 Jul 2004, Jason C. Leach wrote:

> Hi,
>
> Both the RAID (Promise SuperTrak 6000) or the USB subsystems really
> drive the system load up. I'm using a AMD 3200+ system that is only a
> few months old with the 2.4.25 kernel.  When the I/O systems are
> blocking the system is very unresponsive. Some times samba will timeout,
> or I'll wait several seconds for commands like df, top, w and so on.
>
> I am wondering if I were to use a dual CPU system, would this solve my
> I/O blocking problem?  Would one CPU tend to the I/O subsystem and the
> second would deal with other system requests I (samba, DB, LDAP, ...)?
> -
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

Re: I/O Blocking

[berk walker]

Jason C. Leach wrote:

> Hi,
>
> Both the RAID (Promise SuperTrak 6000) or the USB subsystems really 
> drive the system load up. I'm using a AMD 3200+ system that is only a 
> few months old with the 2.4.25 kernel.  When the I/O systems are 
> blocking the system is very unresponsive. Some times samba will 
> timeout, or I'll wait several seconds for commands like df, top, w and 
> so on.
>
> I am wondering if I were to use a dual CPU system, would this solve my 
> I/O blocking problem?  Would one CPU tend to the I/O subsystem and the 
> second would deal with other system requests I (samba, DB, LDAP, ...)?
> -
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
HMMM I seemed to have lost the 1st of the thread, 2 cents worth .. what 
ya pay for ...

I might be supect of the m/b IDE channels (personally had lots of 
failures) - SMART drives that are not configured as SMART (sorry, I 
always use Intel, AMD...?) enableing in bios and kernel or mod might 
give clues.  I, also, think that there must be an IRQ conflict, IRQ 
unanswered, or same ilk.

You could test by  swapping drives, swapping m/b's.  What sizes are your 
disks?  What RAM do you use,, I do have a plethora of hwde I could loan.

b-