94 lines
2.8 KiB
C++
94 lines
2.8 KiB
C++
/*
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* \brief RAM-session client that upgrades its session quota 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) 2006-2013 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__BASE__INTERNAL__EXPANDING_RAM_SESSION_CLIENT_H_
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#define _INCLUDE__BASE__INTERNAL__EXPANDING_RAM_SESSION_CLIENT_H_
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/* Genode includes */
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#include <util/retry.h>
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#include <ram_session/client.h>
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/* base-internal includes */
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#include <base/internal/upgradeable_client.h>
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namespace Genode { class Expanding_ram_session_client; }
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struct Genode::Expanding_ram_session_client : Upgradeable_client<Genode::Ram_session_client>
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{
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Expanding_ram_session_client(Ram_session_capability cap, Parent::Client::Id id)
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: Upgradeable_client<Genode::Ram_session_client>(cap, id) { }
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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 = 2 };
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return retry<Ram_session::Quota_exceeded>(
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[&] () {
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/*
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* If the RAM session runs out of meta data, upgrade the
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* session quota and retry.
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*/
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return retry<Ram_session::Out_of_metadata>(
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[&] () { return Ram_session_client::alloc(size, cached); },
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[&] () { upgrade_ram(8*1024); });
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},
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[&] () {
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char buf[128];
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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 { ALLOC_OVERHEAD = 4096U };
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Genode::snprintf(buf, sizeof(buf), "ram_quota=%lu",
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size + ALLOC_OVERHEAD);
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env_deprecated()->parent()->resource_request(buf);
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},
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NUM_ATTEMPTS);
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}
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int transfer_quota(Ram_session_capability ram_session, size_t amount) override
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{
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enum { NUM_ATTEMPTS = 2 };
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int ret = -1;
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for (unsigned i = 0; i < NUM_ATTEMPTS; i++) {
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ret = Ram_session_client::transfer_quota(ram_session, amount);
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if (ret != -3) break;
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/*
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* The transfer failed 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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* XXX Let transfer_quota throw 'Ram_session::Quota_exceeded'
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*/
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char buf[128];
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Genode::snprintf(buf, sizeof(buf), "ram_quota=%lu", amount);
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env_deprecated()->parent()->resource_request(buf);
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}
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return ret;
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}
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};
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#endif /* _INCLUDE__BASE__INTERNAL__EXPANDING_RAM_SESSION_CLIENT_H_ */
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