I have noticed something strange about the L1/L2 cache size reporting in the
2.4.0 kernel which could need a little explanation.
It looks as if /proc/cpuinfo reports the L2 cache size on a PII, while it
reports the L1 cache size on a K6-2.
Either that, or my external L2 cache is 64kB, and not 512 as it is supposed
to be. memtest86 reports 'cacheable memory' to be 128MB, which is according
to spec. I can verify with lmbench that I *have* a l2 cache, by switching it
on/off in bios. (Larry: any chance of detecting/measuring l2 cache size?)
My friend's system reports:
dmesg:
CPU: Before vendor init, caps: 0183f9ff 00000000 00000000, vendor = 0
CPU: L1 I cache: 16K, L1 D cache: 16K
CPU: L2 cache: 512K
Intel machine check architecture supported.
Intel machine check reporting enabled on CPU#0.
CPU: After vendor init, caps: 0183f9ff 00000000 00000000 00000000
CPU: After generic, caps: 0183f9ff 00000000 00000000 00000000
CPU: Common caps: 0183f9ff 00000000 00000000 00000000
CPU: Intel Pentium II (Deschutes) stepping 01
/proc/cpuinfo:
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 5
model name : Pentium II (Deschutes)
stepping : 1
cpu MHz : 350.799
cache size : 512 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov
pat
pse36 mmx fxsr
bogomips : 699.59
My own system reports:
dmesg:
CPU: Before vendor init, caps: 008021bf 808029bf 00000000, vendor = 2
CPU: L1 I Cache: 32K (32 bytes/line), D cache 32K (32 bytes/line)
CPU: After vendor init, caps: 008021bf 808029bf 00000000 00000002
CPU: After generic, caps: 008021bf 808029bf 00000000 00000002
CPU: Common caps: 008021bf 808029bf 00000000 00000002
CPU: AMD-K6(tm) 3D processor stepping 0c
/proc/cpuinfo:
processor : 0
vendor_id : AuthenticAMD
cpu family : 5
model : 8
model name : AMD-K6(tm) 3D processor
stepping : 12
cpu MHz : 501.121
cache size : 64 KB <-------????
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr mce cx8 pge mmx syscall 3dnow
k6_mtrr
bogomips : 999.42
I also note that performance on this system isn't quite what I would expect
it to be. compiling glibc 2.1.3 takes longer time on my system than on a
PII-366.
A Celeron 300 outperforms the K6 when running 'mpeg2dec -o null'. Is the K6-2
really this bad? Or is it my memory latency/bandwidth which is hurting me?
lmbench data. Notice that the 2nd run is with external cache switched off.
Kernel is 2.4.0-ac6.
*Local* Communication bandwidths in MB/s - bigger is better
-----------------------------------------------------------
Host OS Pipe AF TCP File Mmap Bcopy Bcopy Mem Mem
UNIX reread reread (libc) (hand) read write
--------- ------------- ---- ---- ---- ------ ------ ------ ------ ---- -----
dagb Linux 2.4.0-a 93 56 41 89 272 73 73 272 103
dagb Linux 2.4.0-a 54 38 28 59 270 79 80 270 112
Memory latencies in nanoseconds - smaller is better
(WARNING - may not be correct, check graphs)
---------------------------------------------------
Host OS Mhz L1 $ L2 $ Main mem Guesses
--------- ------------- ---- ----- ------ -------- -------
dagb Linux 2.4.0-a 501 3.996 133 235
dagb Linux 2.4.0-a 501 3.996 233 238 No L2 cache?
Regards,
Dag B
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