[squid-users] What would be the maximum ufs\aufs cache_dir objects?

[Alex Rousskov]

On 07/14/2017 10:47 AM, Amos Jeffries wrote:

> One UFS cache_dir can hold a maximum of (2^27)-1 safely. 

You probably meant to say (2^25)-1 but the actual number is (2^24)-1
because the sfileno is signed. This is why you get 16'777'215 (a.k.a.
0xFFFFFF) as the actual limit.


> The index hash entries are stored as a 32-bit bitmask (sfileno) - with 5
> bits for cache_dir ID and 27 bits for hash of the file details.

The cache index entries are hashed on their keys, not file numbers (of
any kind). The index entry is using 25 bits for the file number, but
IIRC, those 25 bits are never merged/combined with the 7 bits of the
cache_dir ID in any meaningful way.


Alex.

> typedef signed_int32_t sfileno;>     sfileno swap_filen:25; // keep in sync with SwapFilenMax
>     sdirno swap_dirn:7;
> enum { SwapFilenMax = 0xFFFFFF }; // keep in sync with StoreEntry::swap_filen