Create a memory pool for temporary tracepoint probes storage

[lttng-modules.git] / lttng-tp-mempool.h

diff --git a/lttng-tp-mempool.h b/lttng-tp-mempool.h
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+#ifndef LTTNG_TP_MEMPOOL_H
+#define LTTNG_TP_MEMPOOL_H
+
+/*
+ * lttng-tp-mempool.h
+ *
+ * Copyright (C) 2018 Julien Desfossez <jdesfossez@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; only
+ * version 2.1 of the License.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <linux/percpu.h>
+
+#define LTTNG_TP_MEMPOOL_NR_BUF_PER_CPU 4
+#define LTTNG_TP_MEMPOOL_BUF_SIZE 4096
+
+/*
+ * Initialize the pool, only performed once. The pool is a set of
+ * LTTNG_TP_MEMPOOL_NR_BUF_PER_CPU buffers of size LTTNG_TP_MEMPOOL_BUF_SIZE
+ * per-cpu.
+ *
+ * Returns 0 on success, a negative value on error.
+ */
+int lttng_tp_mempool_init(void);
+
+/*
+ * Destroy the pool and free all the memory allocated.
+ */
+void lttng_tp_mempool_destroy(void);
+
+/*
+ * Ask for a buffer on the current cpu.
+ *
+ * The pool is per-cpu, but there is no exclusive access guarantee on the
+ * per-cpu free-list, the caller needs to ensure it cannot get preempted or
+ * interrupted while performing the allocation.
+ *
+ * The maximum size that can be allocated is LTTNG_TP_MEMPOOL_BUF_SIZE, and the
+ * maximum number of buffers allocated simultaneously on the same CPU is
+ * LTTNG_TP_MEMPOOL_NR_BUF_PER_CPU.
+ *
+ * Return a pointer to a buffer on success, NULL on error.
+ */
+void *lttng_tp_mempool_alloc(size_t size);
+
+/*
+ * Release the memory reserved. Same concurrency limitations as the allocation.
+ */
+void lttng_tp_mempool_free(void *ptr);
+
+#endif /* LTTNG_TP_MEMPOOL_H */