Regarding temporary "pauses", perhaps due to using an SD card with an XO

[Chris Marshall]

If I umount the SD card then the hang/pause-s
stop.  Of course, I than have no extra storage space
for the XO.

It would seem that there may be a system
or kernel call that gets blocked by something
related to the SD card mount.

On 10/13/12, Chris Marshall <devel.chm.01 at gmail.com> wrote:
> I too have observed increasingly often "pauses"
> on my XO but have had no idea how or where to
> start to debug the problem.
>
> One thought I had is that the swap file on the SD
> card is the source of the problem (somehow) but
> I still have the pernicious/persistent hanging even
> without using the swapfile.
>
> I'll try with a brand new 16GB SD card to see if
> that helps.
>
> --Chris
>
> On 10/13/12, Mikus Grinbergs <mikus at bga.com> wrote:
>> Lately there has been discussion about using an SD card to expand the
>> "storage" capability of the XO.  [For instance, discussion of when an XO
>> functions as a server, having it keep its database on an SD card.]
>>
>> What I want to mention is that I experience occasional "pauses" on my XO
>> systems (each has a "permanent" SD card, on which I keep Activities,
>> Linux executables, etc.).  I do not know what causes these "pauses", but
>> my best guess is the following (particularly since "pauses" often occur
>> during a CLI command that is "massively" accessing the SD card).
>>
>> My guess:   SD cards have an "embedded chip" which is responsible for
>> "wear levelling" the electronic components used to keep the data.  It
>> does this by internally 'rearranging' "which data block is physically
>> kept where".  I think this 'rearranging' action by the "embedded chip"
>> gets launched (when some 'internal' SD card thresholds are met) during
>> an I/O access by the (XO) host -- and this "rearranging" results in that
>> host's I/O access being DELAYED until the "embedded chip" is done.
>>
>>
>> I have not compared the "performance" (from the user's point of view) of
>> running an Activity "from the SD card" vs. running it "from the XO".
>> But I do have the impression that the duration of the occasional
>> "pauses" which I as a user notice while running "with the SD card" have
>> gotten LONGER as my XOs have migrated to using ever-larger SD cards.
>>
>> mikus
>>
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