Re: [PATCH] Shrinks sizeof(files_struct) and better layout

[Eric Dumazet <dada1@cosmosbay.com>]

Jan Engelhardt a écrit :
>> 2) Reduces the size of (files_struct), using a special 32 bits (or 64bits)
>> embedded_fd_set, instead of a 1024 bits fd_set for the close_on_exec_init and
>> open_fds_init fields. This save some ram (248 bytes per task)
> 
> 
>> as most tasks dont open more than 32 files.
> 
> How do you know, have you done some empirical testing?
> 
20 years working on Unix/linux machines yes :)

Just try this script on your linux machines :

for f in /proc/*/fd; do ls $f|wc -l;done

more than 95% of tasks have less than 32 concurrent files opened.

(I remember working on AT&T Unix in 1985, with a limit of 20 concurrent files 
per process : it was just fine)

Eric