Re: Very slow transfers to/from micro SD card on a RPi B+

[Stephan <stephanwib%googlemail.com@localhost>]

2015-08-19 15:51 GMT+02:00 Thor Lancelot Simon <tls%panix.com@localhost>:
> We should be shipping with DIRHASH turned on.


That´s it - top speed!

/root/test/files> time seq 1 30000|xargs touch
    1.05s real     0.03s user     0.84s system

Is DIRHASH still considered experimental? It fixes one of NetBSD´s
most annoying shortcomings.

FreeBSD received dynamic memory allocation for DIRHASH which might be
even better.



(re-sending this as my editor intermittently distributes HTML mails)


>
> On Tue, Aug 18, 2015 at 04:19:57PM +0000, Michael van Elst wrote:
>> stephanwib%googlemail.com@localhost (Stephan) writes:
>>
>> >This is from an amd64 server box with an aac raid controller.
>>
>> >/root/test/files> time seq 1 10000|xargs touch
>> >    3.10s real     0.01s user     3.07s system
>> >/root/test/files> rm *
>> >/root/test/files> time seq 1 20000|xargs touch
>> >    9.88s real     0.01s user     8.51s system
>> >/root/test/files> rm *
>> >/root/test/files> time seq 1 30000|xargs touch
>> >   23.45s real     0.04s user    20.41s system
>> >/root/test/files> time seq 1 40000|xargs touch
>> >   43.35s real     0.05s user    38.32s system
>>
>> >That is clearly not linear.
>>
>> Each lookup is linear (unless you use DIRHASH), so the total
>> time goes with n^2.
>>
>> --
>> --
>>                                 Michael van Elst
>> Internet: mlelstv%serpens.de@localhost
>>                                 "A potential Snark may lurk in every tree."
>
> --
>   Thor Lancelot Simon                                        tls%panix.com@localhost
>
>   "We cannot usually in social life pursue a single value or a single moral
>    aim, untroubled by the need to compromise with others."      - H.L.A. Hart