svn commit: r340676 - in head/sys: kern sys
Konstantin Belousov
kostikbel at gmail.com
Tue Nov 20 15:08:08 UTC 2018
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);
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