Re: Storage Interface for squid

On Monday 03 June 2002 21:48, Meghna Dhar wrote:

> When considering which file number to give, I cannot see anywhere
> in storeUfsDirMapBitAllocate(), where the directory is considered.
> I am assuming that the directory is decided first and then
> accordingly the file number is decided. If the file number is
> decided on the basis of a bit map, then where do those 2 formula (
> for D1,D2,L1,L2,N) come into picture ?

First the cache_dir is selected.

Then N (the swap file number) is selected.

Finally the namespace of N (0->X) is distributed on the directory
structure of that cache_dir according to the formula given before..
(basic modulo, first L2 files in the first L2 directory, the next L2
files in the next L2 directory, L2 number of L2 directories per L1
directory, ... (only applies to the "ufs" family of store I/O
implementations, other implementations map N to locations on the disk
differently)

The full identity of a swap file is the two integers

a) cache dir number (0-63, as many as you have cache_dir lines in
squid.conf)
b) swap file number

This can be regarded as the equivalence of a (device,inode) identity
number in a standard UNIX filesystem.

The in-memory swap index is the equivalence of a huge single hashed
directory, covering the whole cache (all configured cache_dir lines,
plus memory).

Regards
Henrik
Received on Mon Jun 03 2002 - 15:33:57 MDT