* caching questions with jffs2
@ 2001-12-08 0:20 Carlson, Kristen
2001-12-08 9:51 ` David Woodhouse
0 siblings, 1 reply; 2+ messages in thread
From: Carlson, Kristen @ 2001-12-08 0:20 UTC (permalink / raw)
To: 'linux-mtd@lists.infradead.org'
Hi,
Can someone describe to me the algorithm used for freeing memory that has
been cached due to file activity in jffs2? Is this done as part of the
garbage collector? How long does the cached memory stay around? Is this
tunable?
Thanks,
Kristen Carlson
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: caching questions with jffs2
2001-12-08 0:20 caching questions with jffs2 Carlson, Kristen
@ 2001-12-08 9:51 ` David Woodhouse
0 siblings, 0 replies; 2+ messages in thread
From: David Woodhouse @ 2001-12-08 9:51 UTC (permalink / raw)
To: Carlson, Kristen; +Cc: 'linux-mtd@lists.infradead.org'
kristen.carlson@intel.com said:
> Can someone describe to me the algorithm used for freeing memory that
> has been cached due to file activity in jffs2? Is this done as part
> of the garbage collector? How long does the cached memory stay
> around? Is this tunable?
At all times while mounted, JFFS2 keeps a list of the offsets of each
physical node belonging to each inode.
On read_inode(), it reads each physical node and builds up a full map of
where data are found for each range of bytes in the file.
On read(), it just reads data into the page cache. Normal Linux cache
eviction rules apply to data pages.
On clear_inode(), the extra stuff allocated in read_inode() is freed.
The paper linked from http://sources.redhat.com/jffs2/ may help to shed
light on this.
--
dwmw2
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