9cba459958
This patch improves the accounting for the backing store of session-state meta data. Originally, the session state used to be allocated by a child-local heap partition fed from the child's RAM session. However, whereas this approach was somehow practical from a runtime's (parent's) point of view, the child component could not count on the quota in its own RAM session. I.e., if the Child::heap grew at the parent side, the child's RAM session would magically diminish. This caused two problems. First, it violates assumptions of components like init that carefully manage their RAM resources (and giving most of them away their children). Second, if a child transfers most of its RAM session quota to another RAM session (like init does), the child's RAM session may actually not allow the parent's heap to grow, which is a very difficult error condition to deal with. In the new version, there is no Child::heap anymore. Instead, session states are allocated from the runtime's RAM session. In order to let children pay for these costs, the parent withdraws the local session costs from the session quota donated from the child when the child initiates a new session. Hence, in principle, all components on the route of the session request take a small bite from the session quota to pay for their local book keeping Consequently, the session quota that ends up at the server may become depleted more or less, depending on the route. In the case where the remaining quota is insufficient for the server, the server responds with 'QUOTA_EXCEEDED'. Since this behavior must generally be expected, this patch equips the client-side 'Env::session' implementation with the ability to re-issue session requests with successively growing quota donations. For several of core's services (ROM, IO_MEM, IRQ), the default session quota has now increased by 2 KiB, which should suffice for session requests to up to 3 hops as is the common case for most run scripts. For longer routes, the retry mechanism as described above comes into effect. For the time being, we give a warning whenever the server-side quota check triggers the retry mechanism. The warning may eventually be removed at a later stage.
73 lines
2.1 KiB
C++
73 lines
2.1 KiB
C++
/*
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* \brief Connection to audio service
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* \author Sebastian Sumpf
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* \date 2012-12-20
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*/
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/*
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* Copyright (C) 2012-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__AUDIO_OUT_SESSION__CONNECTION_H_
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#define _INCLUDE__AUDIO_OUT_SESSION__CONNECTION_H_
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#include <audio_out_session/client.h>
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#include <base/connection.h>
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#include <base/allocator.h>
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namespace Audio_out { struct Connection; }
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struct Audio_out::Connection : Genode::Connection<Session>, Audio_out::Session_client
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{
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/**
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* Issue session request
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*
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* \noapi
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*/
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Capability<Audio_out::Session> _session(Genode::Parent &parent, char const *channel)
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{
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return session(parent, "ram_quota=%ld, channel=\"%s\"",
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2*4096 + 2048 + sizeof(Stream), channel);
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}
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/**
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* Constructor
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*
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* \param channel channel identifier (e.g., "front left")
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* \param alloc_signal install 'alloc_signal', the client may then use
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* 'wait_for_alloc' when the stream is full
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* \param progress_signal install progress signal, the client may then
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* call 'wait_for_progress', which is sent when the
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* server processed one or more packets
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*/
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Connection(Genode::Env &env,
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char const *channel,
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bool alloc_signal = true,
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bool progress_signal = false)
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:
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Genode::Connection<Session>(env, _session(env.parent(), channel)),
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Session_client(env.rm(), cap(), alloc_signal, progress_signal)
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{ }
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/**
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* Constructor
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*
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* \noapi
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* \deprecated Use the constructor with 'Env &' as first
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* argument instead
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*/
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Connection(const char *channel,
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bool alloc_signal = true,
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bool progress_signal = false) __attribute__((deprecated))
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:
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Genode::Connection<Session>(_session(*Genode::env_deprecated()->parent(), channel)),
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Session_client(*Genode::env_deprecated()->rm_session(), cap(), alloc_signal, progress_signal)
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{ }
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};
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#endif /* _INCLUDE__AUDIO_OUT_SESSION__CONNECTION_H_ */
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