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PERCPU(9) NetBSD Kernel Developer's Manual PERCPU(9)
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Maintained for NetBSD
by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.
percpu, percpu_alloc, percpu_free, percpu_getref, percpu_putref,
percpu_foreach -- per-CPU storage allocator
typedef void (*percpu_callback_t)(void *, void *, struct cpu_info *);
percpu_free(percpu_t *pc, size_t size);
percpu_foreach(percpu_t *pc, percpu_callback_t cb, void *arg);
The machine-independent percpu interface provides per-CPU, CPU-local mem-
ory reservations to kernel subsystems. percpu_alloc(size) reserves on
each CPU an independent memory region of size bytes that is local to that
CPU, returning a handle (percpu_t) to those regions. A thread may subse-
quently ask for a pointer, p, to the region held by the percpu_t on the
thread's current CPU. Until the thread relinquishes the pointer, or vol-
untarily sleeps, the thread may read or write the region at p without
causing interprocessor memory synchronization.
Call this in thread context to allocate size bytes of local
storage on each CPU. The storage is initialized with zeroes.
Treat this as an expensive operation. percpu_alloc() returns a
handle for the per-CPU storage.
Call this in thread context to return to the system the per-CPU
storage held by pc. size should match the size passed to
percpu_alloc(). When percpu_free() returns, pc is undefined.
Treat this as an expensive operation.
Disable preemption and return a pointer to the storage held by
pc on the local CPU. Use percpu_getref() in either thread or
interrupt context. Follow each percpu_getref() call with a
matching call to percpu_putref().
Indicate that the thread is finished with the pointer returned
by the matching call to percpu_getref(). Re-enables preemption.
percpu_foreach(pc, cb, arg)
On each CPU, for ci the corresponding struct cpu_info * and p
the CPU-local storage held by pc, run (*cb)(p, arg, ci). Call
this in thread context. cb should be non-blocking and fast. Do
not rely on cb to be run on the CPUs in any particular order.
The percpu interface is implemented within the file
atomic_ops(3), kmem(9), pcq(9), pool_cache(9), xcall(9)
The percpu interface first appeared in NetBSD 6.0.
YAMAMOTO Takashi <yamt@NetBSD.org>
NetBSD 9.1 May 31, 2017 NetBSD 9.1