[CentOS] Slow performance

Mon Apr 30 18:13:59 UTC 2007
Ioannis Vranos <ivranos at freemail.gr>

Ashley M. Kirchner wrote:
> 
>    Hi folks.
> 
>    I'm posting this to both the Fedora as well as the CentOS lists in 
> hopes that somewhere, someone can help me figure out what's going on.  I 
> have a dual Xeon 3GHz server that's performing rather slow when it comes 
> to disk activities.
> 
>    The machine is configured with a single 160 GiB OS drive (with CentOS 
> 5.0) and 4x500 GiB drives setup in a RAID-5 configuration.  All drives 
> are setup for 3.0 GiB SATA link, and the motherboard also supports 
> that.  Looking in dmesg when the system comes up, I see that reflected 
> as well:
> 
> ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
> ata1.00: ATA-7, max UDMA/133, 312581808 sectors: LBA48 NCQ (depth 0/32)
> ata1.00: configured for UDMA/133
> scsi1 : ahci
> ata2: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
> ata2.00: ATA-7, max UDMA/133, 976773168 sectors: LBA48 NCQ (depth 0/32)
> ata2.00: configured for UDMA/133
> scsi2 : ahci
> ata3: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
> ata3.00: ATA-7, max UDMA/133, 976773168 sectors: LBA48 NCQ (depth 0/32)
> ata3.00: configured for UDMA/133
> scsi3 : ahci
> ata4: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
> ata4.00: ATA-7, max UDMA/133, 976773168 sectors: LBA48 NCQ (depth 0/32)
> ata4.00: configured for UDMA/133
> scsi4 : ahci
> ata5: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
> ata5.00: ATA-7, max UDMA/133, 976773168 sectors: LBA48 NCQ (depth 0/32)
> ata5.00: configured for UDMA/133
> scsi5 : ahci
> 
> 
>    Now, I don't know what performance numbers *should* be, but on a 1.8 
> GiB copy on the RAID (cp from one location to another on the RAID), it 
> gets done in just under 50 seconds.  If I try to delete the folder 
> afterwards (rm -rf FOLDER) it takes a few seconds to do so, however if I 
> delete the CONTENTS of the folder, it does so within a fraction of a 
> second (but then 'sync' takes a few seconds to catch up.)
> 
>    That same folder that I'm copying contains 452 jpeg files in it, 
> ranging from 2.5 to 6.2 MiB.  Doing some image processing on them is 
> where it takes a long time.  At the moment I'm doing a simple thumbnail 
> creation with the ImageMagick suite (convert FILE -thumbnail "200x200>' 
> `basename FILE .jpg`.th.jpg) and it takes upwards of 8 minutes to 
> complete.  The whole time it's running, 'top' reports the server load as 
> follows: load average: 1.06, 1.00, 0.81  And the CPU usage is around 9%.
> 
>    Interestingly, if I run the same command and have it create .png 
> instead, it takes longer, but I won't go there just yet.  My question 
> is, is this the expected performance on something like this, or should I 
> be able to get better results?  Is there something I should or could do 
> to speed up disk based processes?
> 
>    Or is this something where it's more memory intensive and I need to 
> look at adding more (right now it has 2 GiB of memory.)
> 
> 
>    This problem is causing one of our web sites to time out because it's 
> trying to process hundreds of image files and generate thumbnails, and 
> it's taking forever to do that.  So I'm starting at the bottom of the 
> pile here, hardware.  If it turns out the hardware is fine, and there's 
> nothing else that can be done to speed it up, then I'll move forward to 
> other possible culprits, such as the routines within the site scripts 
> themselves...


At first I would suggest against cross-posting. The two OSes are not 
exactly the same. Also you should specify your exact OS.

Regarding the 2 CPUs, do you have the service irqbalance running? Also 
if not running CentOS 5.0, have you installed the SMP kernel?

Regarding parallel processing, I do not know much about GNU/Linux 
parallelization, however I assume a given script is running on one CPU 
of the two.

Obviously there are others here with more insight about this than me.