Date: Tue, 20 Nov 2018 17:07:56 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: Mateusz Guzik <mjg@FreeBSD.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r340676 - in head/sys: kern sys Message-ID: <20181120150756.GD2378@kib.kiev.ua> In-Reply-To: <201811201458.wAKEwftP033152@repo.freebsd.org> References: <201811201458.wAKEwftP033152@repo.freebsd.org>
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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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