JFFS2: checking CRCs twice!?

[Artem B. Bityuckiy]

On Wed, 12 Jan 2005, Artem B. Bityuckiy wrote:

> > IIUC than mounting a JFFS2 root fs takes so long (6 seconds on my 
> embedded ARM9)
> > cause the CRCs of all blocks/sectors are checked.
> Cause:
> 1. *Some* of CRCs are checked. Nodes has 3 CRCs: (1) Common header CRC, 
> (2) Header CRC, (3) Data CRC. On mount, JFFS2 check only common header 
> CRCs of inode nodes, and all CRCs of direntries. When checking in 
> background, it checks other CRCs.
> 2. On mount, JFFS2 reads blocks fully. So multiply the number of used 
> blocks on the block read time and add this number to your mount time. This 
> should be fixed, IMHO, since we do not needed, for example, read inode 
> node's data.
> 3. It builds different data structures - fragtree list, direntries list. 
Sorry, I'm wrong - fragtree is not built during mount. Ony dirent list. 
And this is only needed to detect inodes nlink. 
> It counts the inode link numbers. This also takes time, especially if you 
> have slow CPU. Here is some room to improvement exist.
> 
> Seems that's all major activities.
> 
> >
> > But then it looks to me that - shortly after boot - the GC thread doing 
> the same
> > again (in background.c), which takes another 6 scondes and slows down 
> the
> > application startup...
> Not the same, it checks CRCs which were not checked during mount.
> 
> > Or am I missing something?
> 
> --
> Best Regards,
> Artem B. Bityuckiy,
> St.-Petersburg, Russia.
> 
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> 

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