inode checkpoints

[Artem B. Bityuckiy]

>>I think the checkpoints shouldn't be created by GC (when it is actually 
>>garbage collecting) because of it will decrease the JFFS2 performance. 
>>GC is called on some write request when there is no space (excluding the 
>>situation when it is called in background by the GC thread). This, it is 
>>bad to load GC by additional work of creating checkpoints since it is 
>>long enough process....
>>
>>What do you think?
> 
> 
> Hmmm. Maybe. But we can write a checkpoint node when we GC a previous
> checkpoint node perhaps? And we can still write checkpoint nodes when
> appropriate from the actual JFFS2 write routines.
> 
I have the following reasons why it is bad to include checkpoint 
writings when garbage collecting:

1. If there is no (or few) space and the GC is called, it is better to 
*obsolete* checkpoints, not to create new ones. :-) So, if there are no 
threads, I don't know how to create checkpoints from GC... In this case 
it is better to create them while writing... But this is additional 
delay for write operations...

So, I propose either:
1. Introduce the option which enables the checkpoint support and 
automatically enables the GC thread.
2. Just use distinct thread for checkpoints.

Do you have other ideas?

-- 
Best Regards,
Artem B. Bityuckiy,
St.-Petersburg, Russia.