142069 - Disk cache uses too much space

Status: RESOLVED FIXED

(Core :: Networking: Cache, defect, P2)

Description

[Robert A. Lentz]

For many months now I have Disk Cache in preferences set to 50000KB with it set
to a specific folder on a specific (FAT, not FAT32) disk partition (used for
swap and Mozilla cache).  I can clear the cache and have more than 100MB
available on that partition but then Mozilla will fill the disk with the cache,
overallocating its limit.  For example, checking "Properties" on the cache
folder right now:  "Size: 22.3 MB   Size on disk: 53.1 MB".

(The behavior this triggers in Mozilla is that moving backwards in the history
will bring up blank pages.  I will be reporting this failure to reload a page
from the net when it is not available from the cache in a separate bug report.)

-Robert

Comment 1

[Boris Zbarsky [:bzbarsky]]

> "Size: 22.3 MB   Size on disk: 53.1 MB".

This means the data only takes up 22.3MB but due to the brokenness of FAT blocks
takes up 53.1MB of the disk...  Mozilla is in fact storing only 22.3MB of data,
which is less than 50000KB.

I suspect this problem will disappear once we go to a single-file cache.

Comment 2

[Warner Young]

Either that, or Mozilla should check the cluster size on the cache partition,
and calculate the size of cache files by rounding up to cluster size.

Comment 3

[Matthias Versen [:Matti]]

-> Cache

Comment 4

[Boris Zbarsky [:bzbarsky]]

Confirming

Comment 5

[gordon]

I expect this problem should be greatly diminished, since we are only storing
data in separate files if that data is greater than 16k.  We still suffer from
some wasted space, but it's much less than before.

Comment 6

[Warner Young]

Can we consider this FIXED?  The actual size on disk is still a little bit over
the cache limit as set in Mozilla, but the 2 amounts are very close now.  In any
case, target milestone is obviously way off.

Comment 7

[gordon]

Yes.  I'm going to mark this FIXED.  I'll continue making improvements in the
disk space accounting, however, in the process of fixing bug 193454.