Re: glibc regression on alpha with 2.34+
Hi again,
just wanted to clarify something I saw in the build logs from the
buildds - imago to be specific.
On 13.12.22 10:33, Frank Scheiner wrote:
[...]
Summarizing it, I'd be grateful if someone could do the bisecting on one
of the buildds or developer machines.
According to the logs on [1] and [2], the machine seems to run w/o Bcache:
```
uname -a
Linux imago 5.8.18-titan-p1+ #63 SMP Sat Jan 8 16:18:01 NZDT 2022 alpha
GNU/Linux
if [ -f /proc/cpuinfo ] ; then cat /proc/cpuinfo ; fi
cpu : Alpha
cpu model : EV68CB
cpu variation : 7
cpu revision : 0
cpu serial number : JA44900165
system type : Titan
system variation : Privateer
system revision : 0
system serial number : AY50901023
cycle frequency [Hz] : 1250000000
timer frequency [Hz] : 1024.00
page size [bytes] : 8192
phys. address bits : 44
max. addr. space # : 255
BogoMIPS : 2480.92
kernel unaligned acc : 0 (pc=0,va=0)
user unaligned acc : 338897612 (pc=200000e100c,va=1200e71cc)
platform string : AlphaServer ES45 Model 1B
cpus detected : 3
cpus active : 3
cpu active mask : 0000000000000007
L1 Icache : 64K, 2-way, 64b line
L1 Dcache : 64K, 2-way, 64b line
L2 cache : n/a
L3 cache : n/a
```
[1]:
https://buildd.debian.org/status/fetch.php?pkg=glibc&arch=alpha&ver=2.34-8&stamp=1662963628&raw=0
[2]:
https://buildd.debian.org/status/fetch.php?pkg=glibc&arch=alpha&ver=2.36-4&stamp=1667607306&raw=0
See "n/a" for the L2 cache line? Is that (1) an error in the kernel not
being able to detect the 16 MiB Bcache of the 1250 MHz processor modules
or (2) is this machine really running w/o active Bcache?
If (2) I don't know how much effect this has on compilation, but I
recently had a similar issue with the DS15 - i.e. Bcache not activated -
and could see a noticable difference in performance for e.g. `7za b`
and `openssl speed -elapsed` when compared to runs with active Bcache later.
Though I found a solution for the DS15, I didn't find anything related
yet for an ES45.
But maybe this is just a kernel bug and the Bcache is active despite
that message. You can check in SRM with `show config | more`:
```
>>>show config | more
hp AlphaStation DS15
[...]
Processors
CPU 0 Alpha EV68CB pass 4.0 1000 MHz 2MB Bcache
[...]
```
If you see "0MB Bcache" something is wrong.
Alternatively the RMC should also be able to tell you the state of the
processors (using the `cpu` command:
```
RMC>cpu
�0;1m
CPU Powerup Status Translation
�0m
EV6 BIST: PASS
CPU ID: 0 (primary)
STR Test: PASS
CSC Test: PASS
PCHIP0 Test: PASS
DIMx Test: PASS
TIG Bus Test: PASS
DPR Test: STARTED - PASS
CPU Speed Test: PASS - 1000MHz
SROM Power-On Time: 12-13-42 09:45:36
SROM Power-On Error: No error
System Bus Speed: 125MHz
Last Synch State Test: PASS
Bcache Size: 2MB
```
). Though I'm not sure how this will look for mutliple processors.
Cheers,
Frank
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