RPi2 i/o blocking and SD card performance

[Luiz Otavio O Souza]

On 9 June 2016 at 10:55, Warner Losh wrote:
>
>> On Jun 9, 2016, at 5:37 AM, Gergely Imreh wrote:
>>
>> Hi,
>>
>> I've been testing FreeBSD 11.0-CURRENT on a RaspberryPi2. I'm relatively
>> new to FreeBSD, and wondering if there's any advice for improving the
>> performance a bit.
>>
>> First, it looks like there's a lot of i/o blocking behaviour going on. For
>> example running MediaWiki on the board, if I compile any ports, the site
>> itself is pretty much unusable (the PHP scripts time out even with 180s
>> timeouts). The strangest thing is that the CPU usage is not at 100% all the
>> way, can be that all 4 cores are ~99% idle, and still everything goes very
>> slow. Once the ports compilation or any other i/o-related task is finished,
>> it's snappy again.

Yeah, the DMA support is suboptimal and only does one block at time,
this is on my TODO list for a while.

>>
>> Any idea why it could be to have such big latency/lag even though the CPU
>> is idle? Is there anything I could test?

Not at this moment, sorry.

Luiz