Am 12.07.2013 10:20, schrieb Kent Overstreet:
> On Fri, Jul 12, 2013 at 08:13:36AM +0200, Stefan Priebe - Profihost AG wrote:
>> Am 12.07.2013 03:55, schrieb Kent Overstreet:
>>> On Thu, Jul 04, 2013 at 10:13:20AM +0200, Stefan Priebe - Profihost AG
>>> wrote:
>>>> Hello list,
>>>>
>>>> while testing bcache i noticed that while writing a big 48GB file the
>>>> sequential cutoff works fine i see only I/O on the disk but not on the
>>>> cache. I thought i would afterwards see a bypassed value of around 48GB
>>>> but it is only 1.2GB.
>>>>
>>>> Is this expected? Is bcache in kernel 3.10 stable for production usage?
>>>
>>> That sounds like a bug, but bcache in 3.10 certainly should be stable
>>> for production usage.
>>>
>>> There can be some weirdness due to the way the stats work, there's a ~13
>>> second update interval (and also the intermediate counters are 32 bit
>>> ints so if you manage to wrap that in 13 seconds you'll lose counts, but
>>> it's counting sectors so I doubt that happened here).
>>
>> Mhm i doubt that too. But if i write 40GB shouldn't i see a bypass value
>> near 40GB? It's just very small.
>>
>>> Does that sound like it might explain what you were seeing, or do you
>>> think there's something else going on?
>> No right no i don't believe that.
>
> Have you noticed any pattern to it? Does it appear to sometimes be right
> and sometimes wrong, or is it always wrong?
It seems that the dirty stats starts with 0 after a reboot but there
might still be some dirty data in it?
> I looked again at the code that updates that value and I'm not coming up
> with any ideas to explain what you're seeing...
Output:
Rawdisk: /dev/sde1 (rawdisk10) | Cachedisk: /dev/sdb4 (bcachessd2)
Read MB/s | Write MB/s | Read MB/s | Write MB/s |
Dirty | Bypassed
(op/s) | (op/s) | (op/s) | (op/s) |
|
0.00 ( 0) | 18.45 ( 119) | 5.57 ( 58) | 6.06 ( 60) |
-16.3M | 68.9M
0.00 ( 0) | 0.00 ( 7) | 0.01 ( 2) | 7.10 ( 39) |
-12.5M | 68.9M
0.00 ( 1) | 0.00 ( 4) | 0.06 ( 8) | 23.29 ( 100) |
-3.1M | 67.9M
0.00 ( 0) | 0.00 ( 7) | 0.04 ( 8) | 21.43 ( 82) |
9.5M | 67.9M
0.04 ( 8) | 0.00 ( 3) | 0.02 ( 3) | 4.81 ( 73) |
11.0M | 67.9M
0.00 ( 0) | 0.64 ( 12) | 0.02 ( 5) | 19.68 ( 139) |
26.9M | 67.9M
0.00 ( 0) | 0.00 ( 5) | 0.02 ( 4) | 4.61 ( 36) |
31.4M | 67.9M
Stefan
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