fds_gc() does not skip pages after first usage of FDS

RE: fds_gc() does not skip pages after first usage of FDS

Elias — Thu, 05 Mar 2020 18:15:18 GMT

I prefer to prevent non-NRF_SUCCESS return codes whenever possible. The fds_stat() strategy sounds like it will work.

RE: fds_gc() does not skip pages after first usage of FDS

Einar Thorsrud — Thu, 05 Mar 2020 08:11:51 GMT

Hi,

[quote user="Elias Simon"]The consequence I was worried about was flash wear. I originally planned to have fds_gc() run once per minute, but this will go through the 10,000 write-erase cycles for flash in just under a week[/quote]

To be honest I did not think of running GC that often. Why do you want to do that? Typically we recomend do run it when you get FDS_ERR_NO_SPACE_IN_FLASH returned when writing of updating a record (also if you get NRF_ERROR_STORAGE_FULL returned from certain peer manager calls, which uses FDS). This minimizes the number of garbage collection runs, saving power and reducing flash wear.

Update: If you do not want to wait for the FDS to be full before doing GC, you can check the amount of free space using fds_stat() regularly, and make a desition on wheater to do GC based on that.

[quote user="Elias Simon"]Will this thread be updated once a fix is developed?[/quote]

I cannot promise that this will be part of the next nRF5 SDK release, so it might take some time. I will try to remember updating this thread if/when it happens, though.

RE: fds_gc() does not skip pages after first usage of FDS

Elias — Wed, 04 Mar 2020 18:26:34 GMT

The consequence I was worried about was flash wear. I originally planned to have fds_gc() run once per minute, but this will go through the 10,000 write-erase cycles for flash in just under a week. Will this thread be updated once a fix is developed?

RE: fds_gc() does not skip pages after first usage of FDS

Einar Thorsrud — Wed, 04 Mar 2020 11:45:47 GMT

Hi,

Thank you for reporting. It seems you are right that this is a bug. Referring to FDS from SDK 16, m_pages[page].can_gc is set to true on line 830 and 958 in fds.c. It is is also set on line 722, by the call to page_scan() if a dirty record exists, but it is never set to false. I have reported it to the SDK team.

I do not see this as a major bug though, and it should not have any significant consequences.