Re: [PATCH] removes filp_count_lock and changes nr_files type toatomic_t

[Eric Dumazet]

Arjan van de Ven a écrit :
> On Thu, 2005-08-25 at 10:45 +0200, Eric Dumazet wrote:
>
> > This patch removes filp_count_lock spinlock, used to protect files_stat.nr_files.
> >
> > Just use atomic_t type and atomic_inc()/atomic_dec() operations.
> >
> > This patch assumes that atomic_read() is a plain {return v->counter;} on all 
> > architectures. (keywords : sysctl, /proc/sys/fs/file-nr, proc_dointvec)
>
>
> this patch adds atomic ops where there were none before

nope... a spinlock/spinunlock contains atomic ops.

> for those architectures that need atomics for read (parisc? arm?)

not today. No atomic needed for read.

> however.. wouldn't it be better to make this a per cpu variable for
> write, and for read iterate or do something smart otherwise?

So on a machine with 256 CPUS, you want to iterate 256 counters ?
nr_files is not heavily touched, no need to expand it.

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