FDS GC seems not to work

[Haruki Kawakami]

Using SDK 13 FDS, I store 6468 byte, that is 1617 words, including FDS header. Of course this size is total. In detail in byte size, this size consists of

(12(header)+ 576) * 7
(12 + 774) * 1
(12 + 691) * 2
(12 + 144) * 1

I set FDS_VIRTUAL_PAGE_SIZE to 1024 and FDS_VIRTUAL_PAGES to 3.

Then, first write with fds_record_write() is success.

However, second write, that is update, with fds_record_update() fails with FDS_ERR_NO_SPACE_IN_FLASH.

I call fds_gc everytime after fds_record_write () or fds_record_update() call.

I assume that fds_record_update() marks the current record as deleted one and write data to new record area, then calling fds_gc() makes the record area marked as deleted available again.

But when I print out debug log in page_has_space() in fds.c, write_offset of page is only incremented, and FDS doesn't seems to reuse deleted page.

Is my thought correct? If so, this phenomenon is bug? If not, how should I update my data?

Thank you.

[emdi]

Hi,

Running GC after fds_record_write() has no effect.

Running GC after fds_record_update() will delete the 'old' copy of the record, if it succeeds.

To have an 'old' copy of the record the fds_record_update() call must have returned FDS_SUCCESS synchronously and then sent out an FDS_EVT_UPDATE event indicating FDS_SUCCESS. Otherwise, the operation is not performed and thus no 'old' record that can be garbge collected is present in flash.

My understanding is that you are not actually able to create a new, updated copy of a record because the fds_record_update() call returns FDS_ERR_NO_SPACE_IN_FLASH which indicates that there is no space for the new copy, therefore the record can't be updated and the 'old' copy marked as dirty.

Regards, emdi

[Haruki Kawakami]

I got running GC after fds_record_write() has no effect.

Then, I'm noticed that I have omitted description a little.

More detail explanation is below.

For initial write of 6468 byte, I use fds_record_write() for 11 times, and all results are FDS_SUCCESS. Then for next write, that is update, of 6468 byte, I use fds_record_update(). The write and update order is below.

1. (12 + 144) * 1
2. (12 + 691) * 2
3. (12 + 774) * 1
4. (12(header)+ 576) * 7

For 1 and first of 2 update execution, fds_record_update() returns FDS_SUCCESS, then for second of 2 execution, fds_record_update() returns FDS_ERR_NO_SPACE_IN_FLASH.

Then I call fds_gc() and call fds_record_update() again, but it returns FDS_ERR_NO_SPACE_IN_FLASH again.

Does fds_gc() only work when all 4096 byte area are marked as deleted? If so, should I set FDS_VIRTUAL_PAGES to 5 (double for my data)?