libsysprof-capture: add mmap()'d ring buffer

This is the start of a ring buffer to coordinate between processes without the overhead of writing directly to files within the inferior process. Instead, the parent process can monitor the ring buffer for framing information and pass that along to the capture writer.
2025-12-31 20:36:25 +00:00 · 2020-02-13 14:37:29 -08:00
parent aca1a6a765
commit 77400c57c1
5 changed files with 883 additions and 0 deletions
--- a/src/libsysprof-capture/mapped-ring-buffer.h
+++ b/src/libsysprof-capture/mapped-ring-buffer.h
@ -0,0 +1,79 @@
+/* mapped-ring-buffer.h
+ *
+ * Copyright 2020 Christian Hergert <chergert@redhat.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+#pragma once
+
+#include <glib.h>
+
+G_BEGIN_DECLS
+
+typedef struct _MappedRingBuffer MappedRingBuffer;
+
+/**
+ * MappedRingBufferCallback:
+ * @data: a pointer into the mapped buffer containing the data frame
+ * @length: the size of @data in bytes
+ * @user_data: closure data provided to mapped_ring_buffer_drain()
+ *
+ * Functions matching this prototype will be called from the
+ * mapped_ring_buffer_drain() function for each data frame read from
+ * the underlying memory mapping.
+ *
+ * If frames were lost because the reader could not keep up, then
+ * @data will be NULL and @length will be the number of frames that
+ * were known to be lost by the peer.
+ *
+ * This function can also be used with mapped_ring_buffer_create_source()
+ * to automatically drain the ring buffer as part of the main loop progress.
+ *
+ * Returns: %TRUE to coninue draining, otherwise %FALSE and draining stops
+ */
+typedef gboolean (*MappedRingBufferCallback) (gconstpointer data,
+                                              gsize         length,
+                                              gpointer      user_data);
+
+G_GNUC_INTERNAL
+MappedRingBuffer *mapped_ring_buffer_new_reader    (gsize                     buffer_size);
+G_GNUC_INTERNAL
+MappedRingBuffer *mapped_ring_buffer_new_writer    (gint                      fd);
+G_GNUC_INTERNAL
+gint              mapped_ring_buffer_get_fd        (MappedRingBuffer         *self);
+G_GNUC_INTERNAL
+MappedRingBuffer *mapped_ring_buffer_ref           (MappedRingBuffer         *self);
+G_GNUC_INTERNAL
+void              mapped_ring_buffer_unref         (MappedRingBuffer         *self);
+G_GNUC_INTERNAL
+gpointer          mapped_ring_buffer_allocate      (MappedRingBuffer         *self,
+                                                    gsize                     length);
+G_GNUC_INTERNAL
+void              mapped_ring_buffer_advance       (MappedRingBuffer         *self,
+                                                    gsize                     length);
+G_GNUC_INTERNAL
+gboolean          mapped_ring_buffer_drain         (MappedRingBuffer         *self,
+                                                    MappedRingBufferCallback  callback,
+                                                    gpointer                  user_data);
+G_GNUC_INTERNAL
+guint             mapped_ring_buffer_create_source (MappedRingBuffer         *self,
+                                                    MappedRingBufferCallback  callback,
+                                                    gpointer                  user_data);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC (MappedRingBuffer, mapped_ring_buffer_unref)
+
+G_END_DECLS