--- /dev/null
+/*
+ *
+ * Copyright 2016 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_IOMGR_RESOURCE_QUOTA_H
+#define GRPC_CORE_LIB_IOMGR_RESOURCE_QUOTA_H
+
+#include <grpc/support/port_platform.h>
+
+#include <grpc/grpc.h>
+
+#include "src/core/lib/debug/trace.h"
+#include "src/core/lib/iomgr/closure.h"
+
+/** \file Tracks resource usage against a pool.
+
+ The current implementation tracks only memory usage, but in the future
+ this may be extended to (for example) threads and file descriptors.
+
+ A grpc_resource_quota represents the pooled resources, and
+ grpc_resource_user instances attach to the quota and consume those
+ resources. They also offer a vector for reclamation: if we become
+ resource constrained, grpc_resource_user instances are asked (in turn) to
+ free up whatever they can so that the system as a whole can make progress.
+
+ There are three kinds of reclamation that take place, in order of increasing
+ invasiveness:
+ - an internal reclamation, where cached resource at the resource user level
+ is returned to the quota
+ - a benign reclamation phase, whereby resources that are in use but are not
+ helping anything make progress are reclaimed
+ - a destructive reclamation, whereby resources that are helping something
+ make progress may be enacted so that at least one part of the system can
+ complete.
+
+ Only one reclamation will be outstanding for a given quota at a given time.
+ On each reclamation attempt, the kinds of reclamation are tried in order of
+ increasing invasiveness, stopping at the first one that succeeds. Thus, on a
+ given reclamation attempt, if internal and benign reclamation both fail, it
+ will wind up doing a destructive reclamation. However, the next reclamation
+ attempt may then be able to get what it needs via internal or benign
+ reclamation, due to resources that may have been freed up by the destructive
+ reclamation in the previous attempt.
+
+ Future work will be to expose the current resource pressure so that back
+ pressure can be applied to avoid reclamation phases starting.
+
+ Resource users own references to resource quotas, and resource quotas
+ maintain lists of users (which users arrange to leave before they are
+ destroyed) */
+
+extern grpc_core::TraceFlag grpc_resource_quota_trace;
+
+// TODO(juanlishen): This is a hack. We need to do real accounting instead of
+// hard coding.
+constexpr size_t GRPC_RESOURCE_QUOTA_CALL_SIZE = 15 * 1024;
+constexpr size_t GRPC_RESOURCE_QUOTA_CHANNEL_SIZE = 50 * 1024;
+
+grpc_resource_quota* grpc_resource_quota_ref_internal(
+ grpc_resource_quota* resource_quota);
+void grpc_resource_quota_unref_internal(grpc_resource_quota* resource_quota);
+grpc_resource_quota* grpc_resource_quota_from_channel_args(
+ const grpc_channel_args* channel_args, bool create = true);
+
+/* Return a number indicating current memory pressure:
+ 0.0 ==> no memory usage
+ 1.0 ==> maximum memory usage */
+double grpc_resource_quota_get_memory_pressure(
+ grpc_resource_quota* resource_quota);
+
+size_t grpc_resource_quota_peek_size(grpc_resource_quota* resource_quota);
+
+typedef struct grpc_resource_user grpc_resource_user;
+
+grpc_resource_user* grpc_resource_user_create(
+ grpc_resource_quota* resource_quota, const char* name);
+
+/* Returns a borrowed reference to the underlying resource quota for this
+ resource user. */
+grpc_resource_quota* grpc_resource_user_quota(
+ grpc_resource_user* resource_user);
+
+void grpc_resource_user_ref(grpc_resource_user* resource_user);
+void grpc_resource_user_unref(grpc_resource_user* resource_user);
+void grpc_resource_user_shutdown(grpc_resource_user* resource_user);
+
+/* Attempts to get quota from the resource_user to create 'thread_count' number
+ * of threads. Returns true if successful (i.e the caller is now free to create
+ * 'thread_count' number of threads) or false if quota is not available */
+bool grpc_resource_user_allocate_threads(grpc_resource_user* resource_user,
+ int thread_count);
+/* Releases 'thread_count' worth of quota back to the resource user. The quota
+ * should have been previously obtained successfully by calling
+ * grpc_resource_user_allocate_threads().
+ *
+ * Note: There need not be an exact one-to-one correspondence between
+ * grpc_resource_user_allocate_threads() and grpc_resource_user_free_threads()
+ * calls. The only requirement is that the number of threads allocated should
+ * all be eventually released */
+void grpc_resource_user_free_threads(grpc_resource_user* resource_user,
+ int thread_count);
+
+/* Allocates from the resource user 'size' worth of memory if this won't exceed
+ * the resource quota's total size. Returns whether the allocation is done
+ * successfully. If allocated successfully, the memory should be freed by the
+ * caller eventually. */
+bool grpc_resource_user_safe_alloc(grpc_resource_user* resource_user,
+ size_t size);
+/* Allocates from the resource user 'size' worth of memory.
+ * If optional_on_done is NULL, then allocate immediately. This may push the
+ * quota over-limit, at which point reclamation will kick in. The caller is
+ * always responsible to free the memory eventually.
+ * If optional_on_done is non-NULL, it will be scheduled without error when the
+ * allocation has been granted by the quota, and the caller is responsible to
+ * free the memory eventually. Or it may be scheduled with an error, in which
+ * case the caller fails to allocate the memory and shouldn't free the memory.
+ */
+void grpc_resource_user_alloc(grpc_resource_user* resource_user, size_t size,
+ grpc_closure* optional_on_done);
+/* Release memory back to the quota */
+void grpc_resource_user_free(grpc_resource_user* resource_user, size_t size);
+/* Post a memory reclaimer to the resource user. Only one benign and one
+ destructive reclaimer can be posted at once. When executed, the reclaimer
+ MUST call grpc_resource_user_finish_reclamation before it completes, to
+ return control to the resource quota. */
+void grpc_resource_user_post_reclaimer(grpc_resource_user* resource_user,
+ bool destructive, grpc_closure* closure);
+/* Finish a reclamation step */
+void grpc_resource_user_finish_reclamation(grpc_resource_user* resource_user);
+
+/* Helper to allocate slices from a resource user */
+typedef struct grpc_resource_user_slice_allocator {
+ /* Closure for when a resource user allocation completes */
+ grpc_closure on_allocated;
+ /* Closure to call when slices have been allocated */
+ grpc_closure on_done;
+ /* Length of slices to allocate on the current request */
+ size_t length;
+ /* Number of slices to allocate on the current request */
+ size_t count;
+ /* Destination for slices to allocate on the current request */
+ grpc_slice_buffer* dest;
+ /* Parent resource user */
+ grpc_resource_user* resource_user;
+} grpc_resource_user_slice_allocator;
+
+/* Initialize a slice allocator.
+ When an allocation is completed, calls \a cb with arg \p. */
+void grpc_resource_user_slice_allocator_init(
+ grpc_resource_user_slice_allocator* slice_allocator,
+ grpc_resource_user* resource_user, grpc_iomgr_cb_func cb, void* p);
+
+/* Allocate \a count slices of length \a length into \a dest. Only one request
+ can be outstanding at a time. */
+void grpc_resource_user_alloc_slices(
+ grpc_resource_user_slice_allocator* slice_allocator, size_t length,
+ size_t count, grpc_slice_buffer* dest);
+
+#endif /* GRPC_CORE_LIB_IOMGR_RESOURCE_QUOTA_H */
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