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This patch facilitates the batching of I/O operations in the VFS library by replacing the implicit wakeup of remote peer (via the traditional packet-stream interface like 'submit_packet') by explicit wakeup signalling. The wakeup signalling is triggered not before the VFS user settles down. E.g., for libc-based applications, this is the case if the libc goes idle, waiting for external I/O. In the case of a busy writer to a non-blocking file descriptor or socket (e.g., lighttpd), the remote peers are woken up once a write operation yields an out-count of 0. The deferring of wakeup signals is accommodated by the new 'Remote_io' mechanism (vfs/remote_io.h) that is designated to be used by all VFS plugins that interact with asynchronous Genode services for I/O. Issue #4697
105 lines
1.9 KiB
C++
105 lines
1.9 KiB
C++
/*
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* \brief Mechanism for waking up remote I/O peers
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* \author Norman Feske
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* \date 2022-12-01
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*/
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/*
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* Copyright (C) 2022 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 Affero General Public License version 3.
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*/
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#ifndef _INCLUDE__VFS__REMOTE_IO_H_
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#define _INCLUDE__VFS__REMOTE_IO_H_
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#include <base/registry.h>
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#include <vfs/types.h>
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namespace Vfs { class Remote_io; }
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struct Vfs::Remote_io : Interface
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{
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virtual void wakeup_remote_peer() = 0;
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class Deferred_wakeups;
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class Peer;
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};
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class Vfs::Remote_io::Peer : Genode::Noncopyable
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{
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private:
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struct Deferred_wakeup;
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using Wakeup_registry = Genode::Registry<Deferred_wakeup>;
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class Deferred_wakeup : Wakeup_registry::Element, Interface
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{
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private:
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Peer &_peer;
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public:
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Deferred_wakeup(Wakeup_registry ®istry, Peer &peer)
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:
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Wakeup_registry::Element(registry, *this), _peer(peer)
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{ }
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void trigger() { _peer._wakeup(); }
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};
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friend class Deferred_wakeups;
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Deferred_wakeups &_deferred_wakeups;
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Remote_io &_remote_io;
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Genode::Constructible<Deferred_wakeup> _deferred_wakeup { };
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void _wakeup()
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{
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_remote_io.wakeup_remote_peer();
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_deferred_wakeup.destruct();
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}
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public:
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Peer(Deferred_wakeups &deferred_wakeups, Remote_io &remote_io)
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:
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_deferred_wakeups(deferred_wakeups), _remote_io(remote_io)
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{ }
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inline void schedule_wakeup();
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};
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class Vfs::Remote_io::Deferred_wakeups : Genode::Noncopyable
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{
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private:
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Peer::Wakeup_registry _registry { };
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friend class Peer;
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public:
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void trigger()
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{
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_registry.for_each([&] (Peer::Deferred_wakeup &deferred_wakeup) {
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deferred_wakeup.trigger(); });
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}
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};
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void Vfs::Remote_io::Peer::schedule_wakeup()
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{
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_deferred_wakeup.construct(_deferred_wakeups._registry, *this);
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}
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#endif /* _INCLUDE__VFS__REMOTE_IO_H_ */
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