a262908acc
This patch adds eviction notices to the caches, to provide accurate tracking of cache blocks in snoop filters. We add the CleanEvict message to the memory heirarchy and use both CleanEvicts and Writebacks with BLOCK_CACHED flags to propagate notice of clean and dirty evictions respectively, down the memory hierarchy. Note that the BLOCK_CACHED flag indicates whether there exist any copies of the evicted block in the caches above the evicting cache. The purpose of the CleanEvict message is to notify snoop filters of silent evictions in the relevant caches. The CleanEvict message behaves much like a Writeback. CleanEvict is a write and a request but unlike a Writeback, CleanEvict does not have data and does not need exclusive access to the block. The cache generates the CleanEvict message on a fill resulting in eviction of a clean block. Before travelling downwards CleanEvict requests generate zero-time snoop requests to check if the same block is cached in upper levels of the memory heirarchy. If the block exists, the cache discards the CleanEvict message. The snoops check the tags, writeback queue and the MSHRs of upper level caches in a manner similar to snoops generated from HardPFReqs. Currently CleanEvicts keep travelling towards main memory unless they encounter the block corresponding to their address or reach main memory (since we have no well defined point of serialisation). Main memory simply discards CleanEvict messages. We have modified the behavior of Writebacks, such that they generate snoops to check for the presence of blocks in upper level caches. It is possible in our current implmentation for a lower level cache to be writing back a block while a shared copy of the same block exists in the upper level cache. If the snoops find the same block in upper level caches, we set the BLOCK_CACHED flag in the Writeback message. We have also added logic to account for interaction of other message types with CleanEvicts waiting in the writeback queue. A simple example is of a response arriving at a cache removing any CleanEvicts to the same address from the cache's writeback queue.
347 lines
14 KiB
C++
Executable file
347 lines
14 KiB
C++
Executable file
/*
|
|
* Copyright (c) 2013 ARM Limited
|
|
* All rights reserved
|
|
*
|
|
* The license below extends only to copyright in the software and shall
|
|
* not be construed as granting a license to any other intellectual
|
|
* property including but not limited to intellectual property relating
|
|
* to a hardware implementation of the functionality of the software
|
|
* licensed hereunder. You may use the software subject to the license
|
|
* terms below provided that you ensure that this notice is replicated
|
|
* unmodified and in its entirety in all distributions of the software,
|
|
* modified or unmodified, in source code or in binary form.
|
|
*
|
|
* Redistribution and use in source and binary forms, with or without
|
|
* modification, are permitted provided that the following conditions are
|
|
* met: redistributions of source code must retain the above copyright
|
|
* notice, this list of conditions and the following disclaimer;
|
|
* redistributions in binary form must reproduce the above copyright
|
|
* notice, this list of conditions and the following disclaimer in the
|
|
* documentation and/or other materials provided with the distribution;
|
|
* neither the name of the copyright holders nor the names of its
|
|
* contributors may be used to endorse or promote products derived from
|
|
* this software without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
|
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
|
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
|
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
*
|
|
* Authors: Stephan Diestelhorst <stephan.diestelhorst@arm.com>
|
|
*/
|
|
|
|
/**
|
|
* @file
|
|
* Definition of a snoop filter.
|
|
*/
|
|
|
|
#include "base/misc.hh"
|
|
#include "base/trace.hh"
|
|
#include "debug/SnoopFilter.hh"
|
|
#include "mem/snoop_filter.hh"
|
|
#include "sim/system.hh"
|
|
|
|
std::pair<SnoopFilter::SnoopList, Cycles>
|
|
SnoopFilter::lookupRequest(const Packet* cpkt, const SlavePort& slave_port)
|
|
{
|
|
DPRINTF(SnoopFilter, "%s: packet src %s addr 0x%x cmd %s\n",
|
|
__func__, slave_port.name(), cpkt->getAddr(), cpkt->cmdString());
|
|
|
|
Addr line_addr = cpkt->getAddr() & ~(linesize - 1);
|
|
SnoopMask req_port = portToMask(slave_port);
|
|
auto sf_it = cachedLocations.find(line_addr);
|
|
bool is_hit = (sf_it != cachedLocations.end());
|
|
// Create a new element through operator[] and modify in-place
|
|
SnoopItem& sf_item = is_hit ? sf_it->second : cachedLocations[line_addr];
|
|
SnoopMask interested = sf_item.holder | sf_item.requested;
|
|
|
|
totRequests++;
|
|
if (is_hit) {
|
|
// Single bit set -> value is a power of two
|
|
if (isPow2(interested))
|
|
hitSingleRequests++;
|
|
else
|
|
hitMultiRequests++;
|
|
}
|
|
|
|
DPRINTF(SnoopFilter, "%s: SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
|
|
if (!cpkt->req->isUncacheable() && cpkt->needsResponse()) {
|
|
if (!cpkt->memInhibitAsserted()) {
|
|
// Max one request per address per port
|
|
panic_if(sf_item.requested & req_port, "double request :( "\
|
|
"SF value %x.%x\n", sf_item.requested, sf_item.holder);
|
|
|
|
// Mark in-flight requests to distinguish later on
|
|
sf_item.requested |= req_port;
|
|
} else {
|
|
// NOTE: The memInhibit might have been asserted by a cache closer
|
|
// to the CPU, already -> the response will not be seen by this
|
|
// filter -> we do not need to keep the in-flight request, but make
|
|
// sure that we know that that cluster has a copy
|
|
panic_if(!(sf_item.holder & req_port), "Need to hold the value!");
|
|
DPRINTF(SnoopFilter, "%s: not marking request. SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
}
|
|
DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
}
|
|
return snoopSelected(maskToPortList(interested & ~req_port), lookupLatency);
|
|
}
|
|
|
|
void
|
|
SnoopFilter::updateRequest(const Packet* cpkt, const SlavePort& slave_port,
|
|
bool will_retry)
|
|
{
|
|
DPRINTF(SnoopFilter, "%s: packet src %s addr 0x%x cmd %s\n",
|
|
__func__, slave_port.name(), cpkt->getAddr(), cpkt->cmdString());
|
|
|
|
if (cpkt->req->isUncacheable())
|
|
return;
|
|
|
|
Addr line_addr = cpkt->getAddr() & ~(linesize - 1);
|
|
SnoopMask req_port = portToMask(slave_port);
|
|
SnoopItem& sf_item = cachedLocations[line_addr];
|
|
|
|
DPRINTF(SnoopFilter, "%s: old SF value %x.%x retry: %i\n",
|
|
__func__, sf_item.requested, sf_item.holder, will_retry);
|
|
|
|
if (will_retry) {
|
|
// Unmark a request that will come again.
|
|
sf_item.requested &= ~req_port;
|
|
return;
|
|
}
|
|
|
|
// will_retry == false
|
|
if (!cpkt->needsResponse()) {
|
|
// Packets that will not evoke a response but still need updates of the
|
|
// snoop filter; WRITEBACKs for now only
|
|
if (cpkt->cmd == MemCmd::Writeback) {
|
|
// make sure that the sender actually had the line
|
|
panic_if(sf_item.requested & req_port, "double request :( "\
|
|
"SF value %x.%x\n", sf_item.requested, sf_item.holder);
|
|
panic_if(!(sf_item.holder & req_port), "requester %x is not a "\
|
|
"holder :( SF value %x.%x\n", req_port,
|
|
sf_item.requested, sf_item.holder);
|
|
// Writebacks -> the sender does not have the line anymore
|
|
sf_item.holder &= ~req_port;
|
|
} else {
|
|
// @todo Add CleanEvicts
|
|
assert(cpkt->cmd == MemCmd::CleanEvict);
|
|
}
|
|
DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
}
|
|
}
|
|
|
|
std::pair<SnoopFilter::SnoopList, Cycles>
|
|
SnoopFilter::lookupSnoop(const Packet* cpkt)
|
|
{
|
|
DPRINTF(SnoopFilter, "%s: packet addr 0x%x cmd %s\n",
|
|
__func__, cpkt->getAddr(), cpkt->cmdString());
|
|
|
|
assert(cpkt->isRequest());
|
|
|
|
// Broadcast / filter upward snoops
|
|
const bool filter_upward = true; // @todo: Make configurable
|
|
|
|
if (!filter_upward)
|
|
return snoopAll(lookupLatency);
|
|
|
|
Addr line_addr = cpkt->getAddr() & ~(linesize - 1);
|
|
auto sf_it = cachedLocations.find(line_addr);
|
|
bool is_hit = (sf_it != cachedLocations.end());
|
|
// Create a new element through operator[] and modify in-place
|
|
SnoopItem& sf_item = is_hit ? sf_it->second : cachedLocations[line_addr];
|
|
|
|
DPRINTF(SnoopFilter, "%s: old SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
|
|
SnoopMask interested = (sf_item.holder | sf_item.requested);
|
|
|
|
totSnoops++;
|
|
if (is_hit) {
|
|
// Single bit set -> value is a power of two
|
|
if (isPow2(interested))
|
|
hitSingleSnoops++;
|
|
else
|
|
hitMultiSnoops++;
|
|
}
|
|
// ReadEx and Writes require both invalidation and exlusivity, while reads
|
|
// require neither. Writebacks on the other hand require exclusivity but
|
|
// not the invalidation. Previously Writebacks did not generate upward
|
|
// snoops so this was never an aissue. Now that Writebacks generate snoops
|
|
// we need to special case for Writebacks.
|
|
assert(cpkt->cmd == MemCmd::Writeback ||
|
|
(cpkt->isInvalidate() == cpkt->needsExclusive()));
|
|
if (cpkt->isInvalidate() && !sf_item.requested) {
|
|
// Early clear of the holder, if no other request is currently going on
|
|
// @todo: This should possibly be updated even though we do not filter
|
|
// upward snoops
|
|
sf_item.holder = 0;
|
|
}
|
|
|
|
DPRINTF(SnoopFilter, "%s: new SF value %x.%x interest: %x \n",
|
|
__func__, sf_item.requested, sf_item.holder, interested);
|
|
|
|
return snoopSelected(maskToPortList(interested), lookupLatency);
|
|
}
|
|
|
|
void
|
|
SnoopFilter::updateSnoopResponse(const Packet* cpkt,
|
|
const SlavePort& rsp_port,
|
|
const SlavePort& req_port)
|
|
{
|
|
DPRINTF(SnoopFilter, "%s: packet rsp %s req %s addr 0x%x cmd %s\n",
|
|
__func__, rsp_port.name(), req_port.name(), cpkt->getAddr(),
|
|
cpkt->cmdString());
|
|
|
|
assert(cpkt->isResponse());
|
|
assert(cpkt->memInhibitAsserted());
|
|
|
|
if (cpkt->req->isUncacheable())
|
|
return;
|
|
|
|
Addr line_addr = cpkt->getAddr() & ~(linesize - 1);
|
|
SnoopMask rsp_mask = portToMask(rsp_port);
|
|
SnoopMask req_mask = portToMask(req_port);
|
|
SnoopItem& sf_item = cachedLocations[line_addr];
|
|
|
|
DPRINTF(SnoopFilter, "%s: old SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
|
|
// The source should have the line
|
|
panic_if(!(sf_item.holder & rsp_mask), "SF value %x.%x does not have "\
|
|
"the line\n", sf_item.requested, sf_item.holder);
|
|
|
|
// The destination should have had a request in
|
|
panic_if(!(sf_item.requested & req_mask), "SF value %x.%x missing "\
|
|
"the original request\n", sf_item.requested, sf_item.holder);
|
|
|
|
// Update the residency of the cache line.
|
|
if (cpkt->needsExclusive() || !cpkt->sharedAsserted()) {
|
|
DPRINTF(SnoopFilter, "%s: dropping %x because needs: %i shared: %i "\
|
|
"SF val: %x.%x\n", __func__, rsp_mask,
|
|
cpkt->needsExclusive(), cpkt->sharedAsserted(),
|
|
sf_item.requested, sf_item.holder);
|
|
|
|
sf_item.holder &= ~rsp_mask;
|
|
// The snoop filter does not see any ACKs from non-responding sharers
|
|
// that have been invalidated :( So below assert would be nice, but..
|
|
//assert(sf_item.holder == 0);
|
|
sf_item.holder = 0;
|
|
}
|
|
assert(cpkt->cmd != MemCmd::Writeback);
|
|
sf_item.holder |= req_mask;
|
|
sf_item.requested &= ~req_mask;
|
|
DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
}
|
|
|
|
void
|
|
SnoopFilter::updateSnoopForward(const Packet* cpkt,
|
|
const SlavePort& rsp_port, const MasterPort& req_port)
|
|
{
|
|
DPRINTF(SnoopFilter, "%s: packet rsp %s req %s addr 0x%x cmd %s\n",
|
|
__func__, rsp_port.name(), req_port.name(), cpkt->getAddr(),
|
|
cpkt->cmdString());
|
|
|
|
Addr line_addr = cpkt->getAddr() & ~(linesize - 1);
|
|
SnoopItem& sf_item = cachedLocations[line_addr];
|
|
SnoopMask rsp_mask M5_VAR_USED = portToMask(rsp_port);
|
|
|
|
assert(cpkt->isResponse());
|
|
assert(cpkt->memInhibitAsserted());
|
|
|
|
DPRINTF(SnoopFilter, "%s: old SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
|
|
// Remote (to this snoop filter) snoops update the filter already when they
|
|
// arrive from below, because we may not see any response.
|
|
if (cpkt->needsExclusive()) {
|
|
// If the request to this snoop response hit an in-flight transaction,
|
|
// the holder was not reset -> no assertion & do that here, now!
|
|
//assert(sf_item.holder == 0);
|
|
sf_item.holder = 0;
|
|
}
|
|
DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
}
|
|
|
|
void
|
|
SnoopFilter::updateResponse(const Packet* cpkt, const SlavePort& slave_port)
|
|
{
|
|
DPRINTF(SnoopFilter, "%s: packet src %s addr 0x%x cmd %s\n",
|
|
__func__, slave_port.name(), cpkt->getAddr(), cpkt->cmdString());
|
|
|
|
assert(cpkt->isResponse());
|
|
|
|
if (cpkt->req->isUncacheable())
|
|
return;
|
|
|
|
Addr line_addr = cpkt->getAddr() & ~(linesize - 1);
|
|
SnoopMask slave_mask = portToMask(slave_port);
|
|
SnoopItem& sf_item = cachedLocations[line_addr];
|
|
|
|
DPRINTF(SnoopFilter, "%s: old SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
|
|
// Make sure we have seen the actual request, too
|
|
panic_if(!(sf_item.requested & slave_mask), "SF value %x.%x missing "\
|
|
"request bit\n", sf_item.requested, sf_item.holder);
|
|
|
|
// Update the residency of the cache line.
|
|
if (cpkt->needsExclusive() || !cpkt->sharedAsserted())
|
|
sf_item.holder = 0;
|
|
sf_item.holder |= slave_mask;
|
|
sf_item.requested &= ~slave_mask;
|
|
DPRINTF(SnoopFilter, "%s: new SF value %x.%x\n",
|
|
__func__, sf_item.requested, sf_item.holder);
|
|
}
|
|
|
|
void
|
|
SnoopFilter::regStats()
|
|
{
|
|
totRequests
|
|
.name(name() + ".tot_requests")
|
|
.desc("Total number of requests made to the snoop filter.");
|
|
|
|
hitSingleRequests
|
|
.name(name() + ".hit_single_requests")
|
|
.desc("Number of requests hitting in the snoop filter with a single "\
|
|
"holder of the requested data.");
|
|
|
|
hitMultiRequests
|
|
.name(name() + ".hit_multi_requests")
|
|
.desc("Number of requests hitting in the snoop filter with multiple "\
|
|
"(>1) holders of the requested data.");
|
|
|
|
totSnoops
|
|
.name(name() + ".tot_snoops")
|
|
.desc("Total number of snoops made to the snoop filter.");
|
|
|
|
hitSingleSnoops
|
|
.name(name() + ".hit_single_snoops")
|
|
.desc("Number of snoops hitting in the snoop filter with a single "\
|
|
"holder of the requested data.");
|
|
|
|
hitMultiSnoops
|
|
.name(name() + ".hit_multi_snoops")
|
|
.desc("Number of snoops hitting in the snoop filter with multiple "\
|
|
"(>1) holders of the requested data.");
|
|
}
|
|
|
|
SnoopFilter *
|
|
SnoopFilterParams::create()
|
|
{
|
|
return new SnoopFilter(this);
|
|
}
|