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SubjectIntel P6 vs P7 system call performance
I have been benchmarking Pentium 4 boxes against my Pentium III laptop
with the exact same kernel and executables as well as custom compiled
kernels. The Pentium III has a much lower clock rate and I have
noticed that system call performance (and hence io performance) is up
to an order of magnitude higher on my Pentium III laptop. 1k block IO
reads/writes are anemic on the Pentium 4, for example, so I'm trying
to figure out why and thought someone might have an idea.

Notice below that the System Call overhead is much higher on the
Pentium 4 even though the cpu runs more than twice the speed and the
system has DDRAM, a 400 Mhz FSB, etc. I even get pretty remarkable
syscall/io performance on my Pentium III laptop vs. an otherwise idle
dual Xeon.

See how the performance is nearly opposite of what one would expect:

----------------------------------------------------------------------
basic sys call performance iterated for 10 secs:
while (1) {
close(dup(0));
getpid();
getuid();
umask(022);
iter++;
}
M-Pentium III 850Mhz Sys Call Rate 433741.8
Pentium 4 2Ghz Sys Call Rate 233637.8
Xeon x 2 2.4Ghz Sys Call Rate 207684.2

----------------------------------------------------------------------
1k read sys calls iterated for 10 secs (all buffered reads, no disk):
M-Pentium III 850Mhz File Read 1492961.0 (~149 io/s)
Pentium 4 2Ghz File Read 1088629.0 (~108 io/s)
Xeon x 2 2.4Ghz File Read 686892.0 (~ 69 io/s)

Any ideas? Not sure I want to upgrade to the P7 architecture if this
is right, since for me system calls are probably more important than
raw cpu computational power.

- Mike

--- Mobile Pentium III 850 Mhz ---
BYTE UNIX Benchmarks (Version 3.11)
System -- Linux flux.loup.net 2.4.7-10 #1 Thu Sep 6 17:27:27 EDT 2001 i686 unknown
Start Benchmark Run: Thu Nov 8 07:55:04 PST 2001
1 interactive users.
Dhrystone 2 without register variables 1652556.1 lps (10 secs, 6 samples)
Dhrystone 2 using register variables 1513809.2 lps (10 secs, 6 samples)
Arithmetic Test (type = arithoh) 3770106.2 lps (10 secs, 6 samples)
Arithmetic Test (type = register) 230897.5 lps (10 secs, 6 samples)
Arithmetic Test (type = short) 230586.1 lps (10 secs, 6 samples)
Arithmetic Test (type = int) 230916.2 lps (10 secs, 6 samples)
Arithmetic Test (type = long) 232229.7 lps (10 secs, 6 samples)
Arithmetic Test (type = float) 222990.2 lps (10 secs, 6 samples)
Arithmetic Test (type = double) 224339.4 lps (10 secs, 6 samples)
System Call Overhead Test 433741.8 lps (10 secs, 6 samples)
Pipe Throughput Test 499465.5 lps (10 secs, 6 samples)
Pipe-based Context Switching Test 229029.2 lps (10 secs, 6 samples)
Process Creation Test 8696.6 lps (10 secs, 6 samples)
Execl Throughput Test 1089.8 lps (9 secs, 6 samples)
File Read (10 seconds) 1492961.0 KBps (10 secs, 6 samples)
File Write (10 seconds) 157663.0 KBps (10 secs, 6 samples)
File Copy (10 seconds) 32516.0 KBps (10 secs, 6 samples)
File Read (30 seconds) 1507645.0 KBps (30 secs, 6 samples)
File Write (30 seconds) 161130.0 KBps (30 secs, 6 samples)
File Copy (30 seconds) 20155.0 KBps (30 secs, 6 samples)
C Compiler Test 491.2 lpm (60 secs, 3 samples)
Shell scripts (1 concurrent) 1315.2 lpm (60 secs, 3 samples)
Shell scripts (2 concurrent) 694.4 lpm (60 secs, 3 samples)
Shell scripts (4 concurrent) 357.1 lpm (60 secs, 3 samples)
Shell scripts (8 concurrent) 180.4 lpm (60 secs, 3 samples)
Dc: sqrt(2) to 99 decimal places 46831.0 lpm (60 secs, 6 samples)
Recursion Test--Tower of Hanoi 20954.1 lps (10 secs, 6 samples)


INDEX VALUES
TEST BASELINE RESULT INDEX

Arithmetic Test (type = double) 2541.7 224339.4 88.3
Dhrystone 2 without register variables 22366.3 1652556.1 73.9
Execl Throughput Test 16.5 1089.8 66.0
File Copy (30 seconds) 179.0 20155.0 112.6
Pipe-based Context Switching Test 1318.5 229029.2 173.7
Shell scripts (8 concurrent) 4.0 180.4 45.1
=========
SUM of 6 items 559.6
AVERAGE 93.3
--- Desktop Pentium 4 2.0 Ghz w/ 266 Mhz DDR ---
BYTE UNIX Benchmarks (Version 3.11)
System -- Linux gw2 2.4.19 #1 Mon Dec 9 05:31:23 GMT-7 2002 i686 unknown
Start Benchmark Run: Mon Dec 9 05:45:47 GMT-7 2002
1 interactive users.
Dhrystone 2 without register variables 2910759.3 lps (10 secs, 6 samples)
Dhrystone 2 using register variables 2928495.6 lps (10 secs, 6 samples)
Arithmetic Test (type = arithoh) 9252565.4 lps (10 secs, 6 samples)
Arithmetic Test (type = register) 498894.3 lps (10 secs, 6 samples)
Arithmetic Test (type = short) 473452.0 lps (10 secs, 6 samples)
Arithmetic Test (type = int) 498956.5 lps (10 secs, 6 samples)
Arithmetic Test (type = long) 498932.0 lps (10 secs, 6 samples)
Arithmetic Test (type = float) 451138.8 lps (10 secs, 6 samples)
Arithmetic Test (type = double) 451106.8 lps (10 secs, 6 samples)
System Call Overhead Test 233637.8 lps (10 secs, 6 samples)
Pipe Throughput Test 437441.1 lps (10 secs, 6 samples)
Pipe-based Context Switching Test 167229.2 lps (10 secs, 6 samples)
Process Creation Test 9407.2 lps (10 secs, 6 samples)
Execl Throughput Test 2158.8 lps (10 secs, 6 samples)
File Read (10 seconds) 1088629.0 KBps (10 secs, 6 samples)
File Write (10 seconds) 472315.0 KBps (10 secs, 6 samples)
File Copy (10 seconds) 10569.0 KBps (10 secs, 6 samples)
File Read (120 seconds) 1089526.0 KBps (120 secs, 6 samples)
File Write (120 seconds) 467028.0 KBps (120 secs, 6 samples)
File Copy (120 seconds) 3541.0 KBps (120 secs, 6 samples)
C Compiler Test 973.9 lpm (60 secs, 3 samples)
Shell scripts (1 concurrent) 2590.8 lpm (60 secs, 3 samples)
Shell scripts (2 concurrent) 1359.6 lpm (60 secs, 3 samples)
Shell scripts (4 concurrent) 696.4 lpm (60 secs, 3 samples)
Shell scripts (8 concurrent) 352.1 lpm (60 secs, 3 samples)
Dc: sqrt(2) to 99 decimal places 99120.4 lpm (60 secs, 6 samples)
Recursion Test--Tower of Hanoi 44857.5 lps (10 secs, 6 samples)


INDEX VALUES
TEST BASELINE RESULT INDEX

Arithmetic Test (type = double) 2541.7 451106.8 177.5
Dhrystone 2 without register variables 22366.3 2910759.3 130.1
Execl Throughput Test 16.5 2158.8 130.8
File Copy (120 seconds) 179.0 3541.0 19.7
Pipe-based Context Switching Test 1318.5 167229.2 126.8
Shell scripts (8 concurrent) 4.0 352.1 88.0
=========
SUM of 6 items 673.0
AVERAGE 112.1

--- Pentium 4 Xeon 2.4 Ghz x 2 w/ 2.4.19 ---
BYTE UNIX Benchmarks (Version 3.11)
System -- Linux brent-xeon 2.4.19-kel #5 SMP Wed Sep 25 03:15:13 GMT 2002 i686 unknown
Start Benchmark Run: Thu Oct 10 03:48:07 MDT 2002
0 interactive users.
Dhrystone 2 without register variables 2200821.4 lps (10 secs, 6 samples)
Dhrystone 2 using register variables 2233296.6 lps (10 secs, 6 samples)
Arithmetic Test (type = arithoh) 7366670.5 lps (10 secs, 6 samples)
Arithmetic Test (type = register) 399261.4 lps (10 secs, 6 samples)
Arithmetic Test (type = short) 361354.7 lps (10 secs, 6 samples)
Arithmetic Test (type = int) 364200.0 lps (10 secs, 6 samples)
Arithmetic Test (type = long) 345292.9 lps (10 secs, 6 samples)
Arithmetic Test (type = float) 539907.7 lps (10 secs, 6 samples)
Arithmetic Test (type = double) 537355.5 lps (10 secs, 6 samples)
System Call Overhead Test 207684.2 lps (10 secs, 6 samples)
Pipe Throughput Test 283868.3 lps (10 secs, 6 samples)
Pipe-based Context Switching Test 98205.6 lps (10 secs, 6 samples)
Process Creation Test 5395.9 lps (10 secs, 6 samples)
Execl Throughput Test 1612.9 lps (9 secs, 6 samples)
File Read (10 seconds) 686892.0 KBps (10 secs, 6 samples)
File Write (10 seconds) 272217.0 KBps (10 secs, 6 samples)
File Copy (10 seconds) 56415.0 KBps (10 secs, 6 samples)
File Read (30 seconds) 681181.0 KBps (30 secs, 6 samples)
File Write (30 seconds) 272351.0 KBps (30 secs, 6 samples)
File Copy (30 seconds) 20611.0 KBps (30 secs, 6 samples)
C Compiler Test 873.5 lpm (60 secs, 3 samples)
Shell scripts (1 concurrent) 2970.1 lpm (60 secs, 3 samples)
Shell scripts (2 concurrent) 1294.2 lpm (60 secs, 3 samples)
Shell scripts (4 concurrent) 845.2 lpm (60 secs, 3 samples)
Shell scripts (8 concurrent) 409.2 lpm (60 secs, 3 samples)
Dc: sqrt(2) to 99 decimal places no measured results
Recursion Test--Tower of Hanoi 33661.9 lps (10 secs, 6 samples)


INDEX VALUES
TEST BASELINE RESULT INDEX

Arithmetic Test (type = double) 2541.7 537355.5 211.4
Dhrystone 2 without register variables 22366.3 2200821.4 98.4
Execl Throughput Test 16.5 1612.9 97.8
File Copy (30 seconds) 179.0 20611.0 115.1
Pipe-based Context Switching Test 1318.5 98205.6 74.5
Shell scripts (8 concurrent) 4.0 409.2 102.3
=========
SUM of 6 items 699.5
AVERAGE 116.6
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