100 lines
2.8 KiB
C++
100 lines
2.8 KiB
C++
/*
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* \brief PD-session client that issues resource requests on demand
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* \author Norman Feske
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* \date 2013-09-25
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*/
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/*
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* Copyright (C) 2006-2017 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__BASE__INTERNAL__EXPANDING_PD_SESSION_CLIENT_H_
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#define _INCLUDE__BASE__INTERNAL__EXPANDING_PD_SESSION_CLIENT_H_
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/* Genode includes */
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#include <util/retry.h>
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#include <pd_session/client.h>
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namespace Genode { class Expanding_pd_session_client; }
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struct Genode::Expanding_pd_session_client : Pd_session_client
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{
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Parent &_parent;
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void _request_ram_from_parent(size_t amount)
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{
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_parent.resource_request(String<128>("ram_quota=", amount).string());
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}
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void _request_caps_from_parent(size_t amount)
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{
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_parent.resource_request(String<128>("cap_quota=", amount).string());
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}
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Expanding_pd_session_client(Parent &parent, Pd_session_capability cap)
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: Pd_session_client(cap), _parent(parent) { }
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Ram_dataspace_capability alloc(size_t size, Cache_attribute cached = UNCACHED) override
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{
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/*
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* If the RAM session runs out of quota, issue a resource request
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* to the parent and retry.
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*/
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enum { NUM_ATTEMPTS = 10 };
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enum { UPGRADE_CAPS = 4 };
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return retry<Out_of_ram>(
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[&] () {
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return retry<Out_of_caps>(
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[&] () { return Pd_session_client::alloc(size, cached); },
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[&] () {
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warning("cap quota exhausted, issuing resource request to parent");
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_request_caps_from_parent(UPGRADE_CAPS);
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},
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NUM_ATTEMPTS);
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},
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[&] () {
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/*
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* The RAM service withdraws the meta data for the allocator
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* from the RAM quota. In the worst case, a new slab block
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* may be needed. To cover the worst case, we need to take
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* this possible overhead into account when requesting
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* additional RAM quota from the parent.
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*
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* Because the worst case almost never happens, we request
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* a bit too much quota for the most time.
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*/
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enum { OVERHEAD = 4096UL };
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_request_ram_from_parent(size + OVERHEAD);
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},
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NUM_ATTEMPTS);
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}
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void transfer_quota(Pd_session_capability pd_session, Ram_quota amount) override
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{
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/*
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* Should the transfer fail because we don't have enough quota, request
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* the needed amount from the parent.
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*/
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enum { NUM_ATTEMPTS = 2 };
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retry<Out_of_ram>(
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[&] () { Pd_session_client::transfer_quota(pd_session, amount); },
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[&] () { _request_ram_from_parent(amount.value); },
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NUM_ATTEMPTS);
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}
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void transfer_quota(Pd_session_capability pd_session, Cap_quota amount) override
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{
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enum { NUM_ATTEMPTS = 2 };
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retry<Out_of_caps>(
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[&] () { Pd_session_client::transfer_quota(pd_session, amount); },
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[&] () { _request_caps_from_parent(amount.value); },
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NUM_ATTEMPTS);
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}
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};
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#endif /* _INCLUDE__BASE__INTERNAL__EXPANDING_PD_SESSION_CLIENT_H_ */
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