Re: [ts-7000] Re: SD Card write delays

[Larry <>]

That doesn't sound right.
You're writing a lot of data, but it's on a different file system from the root.
The kernel should have no need to block while writing to your SD card in this case.
However, it would need to if the driver cache for the SD card fills up.
Maybe that is your problem.
Try creating a large ramdisk partition. Write your files there first, then
copy them to the SD.

Frank Pagliughi wrote:

The root file system is on the internal flash. The SD Card is
initially blank (with one or two ext2 partitions), and just receives
the data.

We're alpha testing so the main app is dumping out a lot of status and
log information, in addition to the actual data.

The status and log info is streaming out to a text file that is
continuously open. Probably something like 20kB / sec worth of info.

The data is in individual files, around 50kB each, written once per
sec (file open, write, close).

- Frank

--- In .com, <.> wrote:
>
> Do you have the root file system on the same card?
> What else is on the card?
> You must be writing a lot of data, is this a log or something you're
writing?
>
> From: "Frank Pagliughi" <fpagliughi@...>
> Date: 2007/08/08 Wed AM 09:46:39 EST
> To: .com
> Subject: [ts-7000] Re: SD Card write delays
>
> Wow, thanks, I never realized there were so many different speeds for
> Flash memory. Went down to the camera store and bought a couple
> different brands of fast SD Cards.
>
> It kind of made the problem worse!
>
> Now the hangups happen less often, but when they do, they are
> significantly longer - like 30 sec!
>
> I can deal with a relatively high thread latency, but I can't believe
> a driver would lock out the whole system for that long.
>
> Frank
>
>
> --- In .com, <leaton10@> wrote:
> >
> > I've seen the same thing on the TS7250, but when writing to the on
> board flash.
> > It's probably the same thing. I imagine interrupts are disabled by
> the kernel when writing to the flash.
> > The SD is probably smarter though. It's probably blocking access
> till it's done.
> > Maybe there is an ioctl call to detect busy you could use
> > You could get a faster SD card.
> > Larry
> >
> > From: "Frank Pagliughi" <fpagliughi@>
> > Date: 2007/08/07 Tue PM 01:44:02 EST
> > To: .com
> > Subject: [ts-7000] SD Card write delays
> >
> > Hey All,
> >
> > I'm using a TS-7260 for a data-logger type of application, using a
> > slightly modified ts11 kernel, the on-board flash for the root file
> > system, with an SD Card mounted.
> >
> > The application writes its data to the SD Card, but the writes
> > occasionally lock up the whole system for something like 8-10 seconds.
> > I'm guessing when a block is being erased/written. Seems that
> > everything running at user level just stops for that time.
> >
> > Is anyone (everyone) else seeing this? Is there a workaround?
> >
> > Any help would be apreciated.
> >
> > Frank
> >
>

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