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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE. .\" SUCH DAMAGE.
.\" .\"
.\" $FreeBSD$ .\" $FreeBSD$
.\" .\"
.Dd March 26, 2017 .Dd July 5, 2018
.Dt DPCPU 9 .Dt DPCPU 9
.Os .Os
.Sh NAME .Sh NAME
.Nm dpcpu .Nm dpcpu
.Nd Kernel Dynamic Per-CPU Memory Allocator .Nd Kernel Dynamic Per-CPU Memory Allocator
.Sh SYNOPSIS .Sh SYNOPSIS
.In sys/pcpu.h .In sys/pcpu.h
.Ss Per-CPU Variable Definition and Declaration .Ss Per-CPU Variable Definition and Declaration
.Fn DPCPU_DEFINE "type" "name" .Fn DPCPU_DEFINE "type" "name"
.Fn DPCPU_DEFINE_STATIC "type" "name"
.Fn DPCPU_DECLARE "type" "name" .Fn DPCPU_DECLARE "type" "name"
.Ss Current CPU Accessor Functions .Ss Current CPU Accessor Functions
.Fn DPCPU_PTR "name" .Fn DPCPU_PTR "name"
.Fn DPCPU_GET "name" .Fn DPCPU_GET "name"
.Fn DPCPU_SET "name" "value" .Fn DPCPU_SET "name" "value"
.Ss Named CPU Accessor Functions .Ss Named CPU Accessor Functions
.Fn DPCPU_ID_PTR "cpu" "name" .Fn DPCPU_ID_PTR "cpu" "name"
.Fn DPCPU_ID_GET "cpu" "name" .Fn DPCPU_ID_GET "cpu" "name"
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.Ed .Ed
.Pp .Pp
Values may also be initialized statically with the definition, causing each Values may also be initialized statically with the definition, causing each
per-CPU instance to be initialized with the value: per-CPU instance to be initialized with the value:
.Bd -literal -offset 1234 .Bd -literal -offset 1234
DPCPU_DEFINE(int, foo_int) = 1; DPCPU_DEFINE(int, foo_int) = 1;
.Ed .Ed
.Pp .Pp
Syntactically, the definition may be treated as a variable. Values that can be defined as
For example, a dynamic per-CPU variable may be declared as .Dv static
.Dv static : must use
.Fn DPCPU_DEFINE_STATIC :
.Bd -literal -offset 1234 .Bd -literal -offset 1234
static DPCPU_DEFINE(int, foo_int); DPCPU_DEFINE_STATIC(int, foo_int);
.Ed .Ed
.Pp .Pp
.Fn DPCPU_DECLARE .Fn DPCPU_DECLARE
produces a declaration of the per-CPU variable suitable for use in header produces a declaration of the per-CPU variable suitable for use in header
files. files.
.Pp .Pp
The current CPU's variable instance can be accessed via The current CPU's variable instance can be accessed via
.Nm DPCPU_PTR .Nm DPCPU_PTR
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.Pp .Pp
For example, it may be desirable to protect access using For example, it may be desirable to protect access using
.Xr critical_section 9 .Xr critical_section 9
to prevent both preemption and migration during use. to prevent both preemption and migration during use.
Alternatively, it may be desirable to cache the CPU ID at the start of a Alternatively, it may be desirable to cache the CPU ID at the start of a
sequence of accesses, using suitable synchronization to make non-atomic sequence of accesses, using suitable synchronization to make non-atomic
sequences safe in the presence of migration. sequences safe in the presence of migration.
.Bd -literal -offset 1234 .Bd -literal -offset 1234
static DPCPU_DEFINE(int, foo_int); DPCPU_DEFINE_STATIC(int, foo_int);
static DPCPU_DEFINE(struct mutex, foo_lock); DPCPU_DEFINE_STATIC(struct mutex, foo_lock);
void void
foo_int_increment(void) foo_int_increment(void)
{ {
int cpu, value; int cpu, value;
/* Safe as atomic access. */ /* Safe as atomic access. */
atomic_add_int(DPCPU_PTR(foo_int), 1); atomic_add_int(DPCPU_PTR(foo_int), 1);
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