Re: slow down in 2.6 vs 2.4

Re: slow down in 2.6 vs 2.4

[Con Kolivas]

Hi Phy

You said:
Over the last two days I have been struggling with
understanding why 2.6.x kernel is slower than
2.4.21/23 kernels.  I think I have a test case which
demostrates this issue.
make times:

2.4.21:
323.68user 56.07system 6:35.77elapsed 95%CPU
(0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (3138783major+3818347minor)pagefaults
0swaps

2.6.7-rc3-s63 (SPA scheduler):
334.01user 69.86system 7:01.47elapsed 95%CPU
(0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (13301major+6931745minor)pagefaults
0swaps

2.6.7-rc3:
336.17user 68.41system 7:02.47elapsed 95%CPU
(0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (13301major+6931745minor)pagefaults
0swaps


----
Your 2.4 compile is showing a massive number of major page faults. Just how big
is this compile you do? Can you try running the 2.6 compile with 

echo 100 > /proc/sys/vm/swappiness

Con

slow down in 2.6 vs 2.4

[Phy Prabab]

Hello!

Over the last two days I have been struggling with
understanding why 2.6.x kernel is slower than
2.4.21/23 kernels.  I think I have a test case which
demostrates this issue.

I have downloaded gcc-3.4.0 and run with this config:
--enable-languages=c,c++ --prefix=/usr/tmp/foo

using gcc-3.2.3 and binutils-2.13.2.1, on IBM x335
w/2x 2.8G Xeon w/8G RAM, no ht[bios killed], using
local file system (XFS):

make times:

2.4.21:
323.68user 56.07system 6:35.77elapsed 95%CPU
(0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (3138783major+3818347minor)pagefaults
0swaps

2.6.7-rc3-s63 (SPA scheduler):
334.01user 69.86system 7:01.47elapsed 95%CPU
(0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (13301major+6931745minor)pagefaults
0swaps

2.6.7-rc3:
336.17user 68.41system 7:02.47elapsed 95%CPU
(0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (13301major+6931745minor)pagefaults
0swaps

Machine:
00:00.0 Host bridge: ServerWorks: Unknown device 0012
(rev 13)
00:00.1 Host bridge: ServerWorks: Unknown device 0012
00:00.2 Host bridge: ServerWorks: Unknown device 0000
00:01.0 VGA compatible controller: ATI Technologies
Inc Rage XL (rev 27)
00:0f.0 Host bridge: ServerWorks CSB5 South Bridge
(rev 93)
00:0f.1 IDE interface: ServerWorks CSB5 IDE Controller
(rev 93)
00:0f.2 USB Controller: ServerWorks OSB4/CSB5 OHCI USB
Controller (rev 05)
00:0f.3 ISA bridge: ServerWorks: Unknown device 0225
00:11.0 Host bridge: ServerWorks: Unknown device 0101
(rev 03)
00:11.2 Host bridge: ServerWorks: Unknown device 0101
(rev 03)
01:01.0 SCSI storage controller: Symbios Logic Inc.
(formerly NCR): Unknown device 0030 (rev 07)
01:02.0 Ethernet controller: Intel Corporation:
Unknown device 100e (rev 02)
02:01.0 Ethernet controller: BROADCOM Corporation:
Unknown device 16a7 (rev 02)
02:02.0 Ethernet controller: BROADCOM Corporation:
Unknown device 16a7 (rev 02)


Anything else needed? Is there something I can do to
try and understand this issue?

Thank you for your time.
Phy


	
		
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Re: slow down in 2.6 vs 2.4

[Phy Prabab]

Oh, there is an important bit of information missing,
the test is compiling gcc-3.4.0 using gcc-3.2.3 with
binutils-2.13.2.1.  The machine used is a dual 2.8GHz
Xeon w/8G RAM (no ht).

config line is --enable-languages=c,c++
--prefix=/usr/tmp/foo

BTW, the unit never swaps when building.

Thanks!
Phy

--- Con Kolivas <kernel@kolivas.org> wrote:
> 
> Hi Phy
> 
> You said:
> Over the last two days I have been struggling with
> understanding why 2.6.x kernel is slower than
> 2.4.21/23 kernels.  I think I have a test case which
> demostrates this issue.
> make times:
> 
> 2.4.21:
> 323.68user 56.07system 6:35.77elapsed 95%CPU
> (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs
> (3138783major+3818347minor)pagefaults
> 0swaps
> 
> 2.6.7-rc3-s63 (SPA scheduler):
> 334.01user 69.86system 7:01.47elapsed 95%CPU
> (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (13301major+6931745minor)pagefaults
> 0swaps
> 
> 2.6.7-rc3:
> 336.17user 68.41system 7:02.47elapsed 95%CPU
> (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (13301major+6931745minor)pagefaults
> 0swaps
> 
> 
> ----
> Your 2.4 compile is showing a massive number of
> major page faults. Just how big
> is this compile you do? Can you try running the 2.6
> compile with 
> 
> echo 100 > /proc/sys/vm/swappiness
> 
> Con
> 


	
		
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Re: slow down in 2.6 vs 2.4

[Peter Williams]

Con Kolivas wrote:
> Hi Phy
> 
> You said:
> Over the last two days I have been struggling with
> understanding why 2.6.x kernel is slower than
> 2.4.21/23 kernels.  I think I have a test case which
> demostrates this issue.
> make times:
> 
> 2.4.21:
> 323.68user 56.07system 6:35.77elapsed 95%CPU
> (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (3138783major+3818347minor)pagefaults
> 0swaps
> 
> 2.6.7-rc3-s63 (SPA scheduler):
> 334.01user 69.86system 7:01.47elapsed 95%CPU
> (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (13301major+6931745minor)pagefaults
> 0swaps
> 
> 2.6.7-rc3:
> 336.17user 68.41system 7:02.47elapsed 95%CPU
> (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (13301major+6931745minor)pagefaults
> 0swaps
> 
> 
> ----
> Your 2.4 compile is showing a massive number of major page faults.

Seems to be roughly the same total number of page faults in all three 
cases but there's been a big shift from majors to minors for the 2.6 
kernels which I would have thought would improve performance?

Peter
-- 
Dr Peter Williams                                pwil3058@bigpond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
  -- Ambrose Bierce

Re: slow down in 2.6 vs 2.4

[Clint Byrum]

On Tuesday, June 8, 2004, at 08:35 PM, Phy Prabab wrote:

> Hello!
>
> Over the last two days I have been struggling with
> understanding why 2.6.x kernel is slower than
> 2.4.21/23 kernels.  I think I have a test case which
> demostrates this issue.
>

Phy, you and I have corresponded off list. I think we are experiencing 
the same thing...

>
> 2.4.21:
> 323.68user 56.07system 6:35.77elapsed 95%CPU
> (0avgtext+0avgdata 0maxresident)k
> 0inputs+0outputs (3138783major+3818347minor)pagefaults
> 0swaps

Is there any way to get similar numbers system wide on 2.4? This exists 
for 2.6.x, and the latest sysstat shows it with sar -B, but as the sar 
manpage states, the fault/s numbers are not available on 2.4. :(

Stats for a recent period:

Linux 2.4.23 (xxx)       06/09/2004

11:40:00 AM  pgpgin/s pgpgout/s   fault/s  majflt/s
11:50:00 AM     17.52     72.34      0.00      0.00
12:00:00 PM     20.93     65.06      0.00      0.00
Average:        19.22     68.70      0.00      0.00

Linux 2.6.6 (yyy)        06/09/04

11:40:00     pgpgin/s pgpgout/s   fault/s  majflt/s
11:50:00        70.68     81.13  13756.37      0.02
12:00:00        89.22     81.82  11598.21      0.03
Average:        79.95     81.48  12676.43      0.03


Thats from two different boxes.. see my earlier message this week for 
an explanation of the setup.

Re: slow down in 2.6 vs 2.4

[Paul Dickson]

You might check out this URL:

    http://www.usenix.org/publications/library/proceedings/als01/full_papers/ezolt/ezolt_html/

It may not be directly relevent even though the discussed problem is
similar, but the tips on how to break down the problem more than likely
are.

	-Paul

Re: slow down in 2.6 vs 2.4

[Bill Davidsen]

Phy Prabab wrote:
> Hello!
> 
> Over the last two days I have been struggling with
> understanding why 2.6.x kernel is slower than
> 2.4.21/23 kernels.  I think I have a test case which
> demostrates this issue.

Unfortunately this is common. There are a bunch or tunables like 
swappiness and readahead you can adjust, but if anyone has a handle on 
why it's really so slow they don't seem to have gotten a patch out.

On features 2.6 wins, on performance 2.4 seems faster in many cases.

-- 
    -bill davidsen (davidsen@tmr.com)
"The secret to procrastination is to put things off until the
  last possible moment - but no longer"  -me