Re: NFS on Raspberry Pi high load
Hi.
On Fri, Jun 19, 2015 at 02:47:20PM +0200, Petter Adsen wrote:
> On Fri, 19 Jun 2015 14:09:45 +0200
> basti <black.fledermaus@arcor.de> wrote:
>
> > The Problem is not the speed of 3 MB/s it's the load of 12 and more.
> >
> > On 19.06.2015 14:03, Sven Hartge wrote:
> > > basti <black.fledermaus@arcor.de> wrote:
> > >
> > >> iotop show me a read speed around 3 MB/s, there is a Class 10 UHS card
> > >> (10-15 MB/s read, 9-5 MB/s write I guess).
> > > More than 3MByte/s is not really achievable with a Pi-1, because the CPU
> > > is very weak and the Ethernet-Chip is attached via USB.
> > >
> > > Under the best conditions you may be able to transfer up to 45MBit/s,
> > > but a maximum transfer rate of about 35MBit/s is normal.
>
> The load is so high because USB is very CPU-intensive. If you were to
> use the on-board Ethernet, you would not see such a high load.
What? Are you serious? I have this Nokia N900 lying behind me which is
connected by IP-via-USB (aka usbnet aka g_ether) and with the order of
magnitude slower ARM CPU it reliably shows 40mbps with no noticeable
load.
There are countless things I'd blame in this situation (large amounts of
sync I/O from knfsd, relatively small amount of memory for a NFS server,
HUEG read/write latency of MMC card), but blaming the type of Ethernet
connection is the last thing I'd do.
Regardless, there's a way to see the cause of all this trouble.
Relatively new, but demonstrative one:
perf record --a
perf report perf.data
Reco
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