svn commit: r340676 - in head/sys: kern sys

[Konstantin Belousov]

On Tue, Nov 20, 2018 at 02:58:41PM +0000, Mateusz Guzik wrote:
> Author: mjg
> Date: Tue Nov 20 14:58:41 2018
> New Revision: 340676
> URL: https://svnweb.freebsd.org/changeset/base/340676
> 
> Log:
>   Implement unr64
>   
>   Important users of unr like tmpfs or pipes can get away with just
>   ever-increasing counters, making the overhead of managing the state
>   for 32 bit counters a pessimization.
>   
>   Change it to an atomic variable. This can be further sped up by making
>   the counts variable "allocate" ranges and store them per-cpu.
>   
>   Reviewed by:	kib
>   Sponsored by:	The FreeBSD Foundation
>   Differential Revision:	https://reviews.freebsd.org/D18054
> 
> Modified:
>   head/sys/kern/subr_unit.c
>   head/sys/sys/systm.h
> 
> Modified: head/sys/kern/subr_unit.c
> ==============================================================================
> --- head/sys/kern/subr_unit.c	Tue Nov 20 14:52:43 2018	(r340675)
> +++ head/sys/kern/subr_unit.c	Tue Nov 20 14:58:41 2018	(r340676)
> @@ -98,6 +98,19 @@ static struct mtx unitmtx;
>  
>  MTX_SYSINIT(unit, &unitmtx, "unit# allocation", MTX_DEF);
>  
> +#ifdef UNR64_LOCKED
> +uint64_t
> +alloc_unr64(struct unrhdr64 *unr64)
> +{
> +	uint64_t item;
> +
> +	mtx_lock(&unitmtx);
> +	item = unr64->counter++;
> +	mtx_unlock(&unitmtx);
> +	return (item);
> +}
> +#endif
> +
>  #else /* ...USERLAND */
>  
>  #include <bitstring.h>
> 
> Modified: head/sys/sys/systm.h
> ==============================================================================
> --- head/sys/sys/systm.h	Tue Nov 20 14:52:43 2018	(r340675)
> +++ head/sys/sys/systm.h	Tue Nov 20 14:58:41 2018	(r340676)
> @@ -523,6 +523,32 @@ int alloc_unr_specific(struct unrhdr *uh, u_int item);
>  int alloc_unrl(struct unrhdr *uh);
>  void free_unr(struct unrhdr *uh, u_int item);
>  
> +#if defined(__mips__) || defined(__powerpc__)
Please note what I asked about this #ifdefs in the review. mips
and powerpc machine/atomic.h should define some symbol like
__ATOMIC_NO_64_OPS and this case should be handled in less arch-explicit
manner.

> +#define UNR64_LOCKED
> +#endif
> +
> +struct unrhdr64 {
> +        uint64_t	counter;
> +};
> +
> +static __inline void
> +new_unrhdr64(struct unrhdr64 *unr64, uint64_t low)
> +{
> +
> +	unr64->counter = low;
> +}
> +
> +#ifdef UNR64_LOCKED
> +uint64_t alloc_unr64(struct unrhdr64 *);
> +#else
> +static __inline uint64_t
> +alloc_unr64(struct unrhdr64 *unr64)
> +{
> +
> +	return (atomic_fetchadd_64(&unr64->counter, 1));
> +}
> +#endif
> +
>  void	intr_prof_stack_use(struct thread *td, struct trapframe *frame);
>  
>  void counted_warning(unsigned *counter, const char *msg);