571091 - Change smallest disk cache block to 512 bytes

Status: RESOLVED WONTFIX

(Core :: Networking: Cache, enhancement)

Description

[Steve Chapel]

According to bug 569709 comment 18, the average disk cache block holds significantly less than 1 KB of data. Changing the smallest disk cache block size from 1 KB to 512 bytes should save disk space wasted.

Comment 1

[Jason Duell]

Obviously we'll need to measure performance as well.

I *believe* (I really should know this--Michal?) that cache items are not stored compressed.  If not, we should file a bug to explore doing that, and that would presumably reduce the average cache block size further, and also alter performance.

Comment 2

[(no longer active)]

No, they're not stored compressed.

Comment 3

[James May [:fowl2]]

Some (newer) disks have a 4K sector size. Wouldn't using something smaller than that cause problems on those systems?

Comment 4

[Michal Novotny [:michal]]

(In reply to comment #1)
> I *believe* (I really should know this--Michal?) that cache items are not
> stored compressed.

We are not compressing them. But if we receive them as e.g. Content-Encoding: gzip they are compressed.

Comment 5

[Alexandre Folle de Menezes]

I believe compression can be specially useful on Android, where the cache is stored in slow Flash memory.  But it is a separate issue from this one, and should have its own bug.

Comment 6

[Patrick McManus [:mcmanus]]

whole new cache code