Re: [RFC][PATCH 0/5] Optimize percpu-rwsem

[Oleg Nesterov]

On 06/05, Al Viro wrote:
>
> FWIW, I hadn't really looked into stop_machine uses, but fs/locks.c one
> is really not all that great - there we have a large trashcan of a list
> (every file_lock on the system) and the only use of that list is /proc/locks
> output generation.  Sure, additions take this CPU's spinlock.  And removals
> take pretty much a random one - losing the timeslice and regaining it on
> a different CPU is quite likely with the uses there.
>
> Why do we need a global lock there, anyway?  Why not hold only one for
> the chain currently being traversed?  Sure, we'll need to get and drop
> them in ->next() that way; so what?

And note that fs/seq_file.c:seq_hlist_next_percpu() has no other users.

And given that locks_delete_global_locks() takes the random lock anyway,
perhaps the hashed lists/locking makes no sense, I dunno.

Oleg.

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