Re: Production comparison between 2.4.27 and 2.6.8.1

[Nick Piggin]

Massimo Cetra wrote:
> Hi everybody.
>
> #***********************************************************
>
> Environment:
> processor       : 0
> vendor_id       : AuthenticAMD
> cpu family      : 6
> model           : 10
> model name      : AMD Athlon(tm) XP 3000+
> stepping        : 0
> cpu MHz         : 2091.477
>
> #***********************************************************
>              total       used       free     shared    buffers
> cached
> Mem:       1030844     258500     772344          0      36924
> 167092
> -/+ buffers/cache:      54484     976360
> Swap:      2056304          0    2056304
>
> #***********************************************************
> # lspci
> 0000:00:00.0 Host bridge: nVidia Corporation nForce2 AGP (different
> version?) (rev c1)
> 0000:00:00.1 RAM memory: nVidia Corporation nForce2 Memory Controller 1
> (rev c1)
> 0000:00:00.2 RAM memory: nVidia Corporation nForce2 Memory Controller 4
> (rev c1)
> 0000:00:00.3 RAM memory: nVidia Corporation nForce2 Memory Controller 3
> (rev c1)
> 0000:00:00.4 RAM memory: nVidia Corporation nForce2 Memory Controller 2
> (rev c1)
> 0000:00:00.5 RAM memory: nVidia Corporation nForce2 Memory Controller 5
> (rev c1)
> 0000:00:01.0 ISA bridge: nVidia Corporation nForce2 ISA Bridge (rev a4)
> 0000:00:01.1 SMBus: nVidia Corporation nForce2 SMBus (MCP) (rev a2)
> 0000:00:02.0 USB Controller: nVidia Corporation nForce2 USB Controller
> (rev a4)
> 0000:00:02.1 USB Controller: nVidia Corporation nForce2 USB Controller
> (rev a4)
> 0000:00:02.2 USB Controller: nVidia Corporation nForce2 USB Controller
> (rev a4)
> 0000:00:04.0 Ethernet controller: nVidia Corporation nForce2 Ethernet
> Controller (rev a1)
> 0000:00:08.0 PCI bridge: nVidia Corporation nForce2 External PCI Bridge
> (rev a3)
> 0000:00:09.0 IDE interface: nVidia Corporation nForce2 IDE (rev a2)
> 0000:00:1e.0 PCI bridge: nVidia Corporation nForce2 AGP (rev c1)
> 0000:01:04.0 Ethernet controller: Marvell Technology Group Ltd. Yukon
> Gigabit Ethernet 10/100/1000Base-T Adapter (rev 13)
> 0000:01:0b.0 RAID bus controller: Silicon Image, Inc. (formerly CMD
> Technology Inc) SiI 3112 [SATALink/SATARaid] Serial ATA Controller (rev
> 02)
> 0000:03:00.0 VGA compatible controller: nVidia Corporation NV11
> [GeForce2 MX/MX 400] (rev b2)
>
> #***********************************************************
>
> Distro is Debian Woody with all necessary packages backported in order
> to have 2.6 working.
>
> I used postgres 7.4.3 to make some tests on a server which will go in
> producton in a short time.
>
> The test was really simple:
>
> dropdb mydb
> createdb mydb
> time psql -U blus mydb <schema.sql
> time psql -U blus mydb <data.sql
>
> #***********************************************************
>
> I tried both 2.6.8.1 vanilla and 2.4.7 with -lck patches applied and run
> the same test changing kernels.
>
> Tests were run:
> - on a raid1 partition on 2 serial Ata disks	(ext3) [software raid)
> - on a non raid partition on /dev/sda0 (xfs)
>
> (only postgres data has been switched from raid-ext3 to xfs)
>
>
> My purpose was merely have a difference of time between the 2 kernels in
> performing that task.
>
> Case 1a is 2.4.27-lck1 with raid1 ext3
> Case 1b is 2.4.27-lck1 without raid on xfs
> Case 2a is 2.6.8.1 with raid1 ext3
> Case 2b is 2.6.8.1 without raid on xfs
> Results were:
>
> A) for creating the schema (which involves creating tables and indexes)
> 1a:
>   real    0m1.312s
>   user    0m0.030s
>   sys     0m0.008s
> 1b:
>   real    0m0.508s
>   user    0m0.024s
>   sys     0m0.012s
> 2a:
>   real    0m0.941s
>   user    0m0.025s
>   sys     0m0.010s
> 2b:
>   real    0m0.560s
>   user    0m0.024s
>   sys     0m0.005s
>
> B) to import the data (which implies both writing data to disk and
> recalculating indexes)
> 1a:
>   real    4m12.757s
>   user    0m3.376s
>   sys     0m1.700s
> 1b:
>   real    1m0.467s
>   user    0m3.290s
>   sys     0m1.646s
> 2a:
>   real    2m42.861s
>   user    0m3.590s
>   sys     0m1.523s
> 2b:
>   real    1m30.746s
>   user    0m3.255s
>   sys     0m1.501s
>
> #**********************************************
> HDPARM shows:
> # hdparm -v
> hdparm - get/set hard disk parameters - version v5.5
>
> 2.4.7:
> /dev/sda:
>  Timing buffer-cache reads:   2188 MB in  2.00 seconds = 1094.00 MB/sec
>  Timing buffered disk reads:  164 MB in  3.02 seconds =  54.34 MB/sec
>
> 2.6.8.1:
> /dev/sda:
>  Timing buffer-cache reads:   2176 MB in  2.00 seconds = 1087.08 MB/sec
>  Timing buffered disk reads:  136 MB in  3.04 seconds =  44.77 MB/sec
>
> #**********************************************
> It is my first experience with 2.6 branch kernels, because i am trying
> to figure out if the tree is performing well to switch everithing in
> production, so my ideas may be wrong...
>
> Raid tests may be faked because of the overhead caused by md sync (and
> probably raid is better on 2.6). 
> However it seems that libsata has better performance on 2.4 (hdparm)
> xfs tests shows that 2.4 has better performance if compared to 2.6 and
> the difference, in my opinion, is not linked on libsata better
> performance.
>
> What is your opinion ?
> What can I try to improve performance ?

I wouldn't worry too much about hdparm measurements. If you want to
test the streaming throughput of the disk, run dd if=big-file of=/dev/null
or a large write+sync.

Regarding your worse non-RAID XFS database results, try booting 2.6 with
elevator=deadline and test again. If yes, are you using queueing (TCQ) on
your disks?
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