From 5570aa9e9afd7392d561b02081560dfe90dca3f5 Mon Sep 17 00:00:00 2001 From: Andreas Hansson Date: Fri, 25 Sep 2015 07:26:57 -0400 Subject: [PATCH] mem: Comment clean-up for the snoop filter Merely fixing up some style issues and adding more comments. --- src/mem/snoop_filter.cc | 4 +- src/mem/snoop_filter.hh | 89 ++++++++++++++++++++++++----------------- 2 files changed, 54 insertions(+), 39 deletions(-) diff --git a/src/mem/snoop_filter.cc b/src/mem/snoop_filter.cc index d6e74cf0a..55763998a 100755 --- a/src/mem/snoop_filter.cc +++ b/src/mem/snoop_filter.cc @@ -34,12 +34,12 @@ * (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 + * Authors: Stephan Diestelhorst */ /** * @file - * Definition of a snoop filter. + * Implementation of a snoop filter. */ #include "base/misc.hh" diff --git a/src/mem/snoop_filter.hh b/src/mem/snoop_filter.hh index 557ee9a80..407b6f7f1 100755 --- a/src/mem/snoop_filter.hh +++ b/src/mem/snoop_filter.hh @@ -34,7 +34,7 @@ * (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 + * Authors: Stephan Diestelhorst */ /** @@ -96,8 +96,8 @@ class SnoopFilter : public SimObject { } /** - * Init a new snoop filter and tell it about all the - * slave ports of the enclosing bus. + * Init a new snoop filter and tell it about all the slave ports + * of the enclosing bus. * * @param slave_ports Slave ports that the bus is attached to. */ @@ -127,7 +127,7 @@ class SnoopFilter : public SimObject { * call finishRequest once it is known if the request needs to * retry or not. * - * @param cpkt Pointer to the request packet. Not changed. + * @param cpkt Pointer to the request packet. Not changed. * @param slave_port Slave port where the request came from. * @return Pair of a vector of snoop target ports and lookup latency. */ @@ -141,14 +141,15 @@ class SnoopFilter : public SimObject { * reqLookupResult. * * @param will_retry This request will retry on this bus / snoop filter - * @param cpkt Request packet, merely for sanity checking + * @param cpkt Request packet, merely for sanity checking */ void finishRequest(bool will_retry, const Packet* cpkt); /** - * Handle an incoming snoop from below (the master port). These can upgrade the - * tracking logic and may also benefit from additional steering thanks to the - * snoop filter. + * Handle an incoming snoop from below (the master port). These + * can upgrade the tracking logic and may also benefit from + * additional steering thanks to the snoop filter. + * * @param cpkt Pointer to const Packet containing the snoop. * @return Pair with a vector of SlavePorts that need snooping and a lookup * latency. @@ -156,9 +157,9 @@ class SnoopFilter : public SimObject { std::pair lookupSnoop(const Packet* cpkt); /** - * Let the snoop filter see any snoop responses that turn into request responses - * and indicate cache to cache transfers. These will update the corresponding - * state in the filter. + * Let the snoop filter see any snoop responses that turn into + * request responses and indicate cache to cache transfers. These + * will update the corresponding state in the filter. * * @param cpkt Pointer to const Packet holding the snoop response. * @param rsp_port SlavePort that sends the response. @@ -169,28 +170,58 @@ class SnoopFilter : public SimObject { const SlavePort& req_port); /** - * Pass snoop responses that travel downward through the snoop filter and let - * them update the snoop filter state. No additional routing happens. + * Pass snoop responses that travel downward through the snoop + * filter and let them update the snoop filter state. No + * additional routing happens. * * @param cpkt Pointer to const Packet holding the snoop response. * @param rsp_port SlavePort that sends the response. - * @param req_port MasterPort through which the response leaves this cluster. + * @param req_port MasterPort through which the response is forwarded. */ void updateSnoopForward(const Packet *cpkt, const SlavePort& rsp_port, const MasterPort& req_port); /** - * Update the snoop filter with a response from below (outer / other cache, - * or memory) and update the tracking information in the snoop filter. + * Update the snoop filter with a response from below (outer / + * other cache, or memory) and update the tracking information in + * the snoop filter. * * @param cpkt Pointer to const Packet holding the snoop response. - * @param slave_port SlavePort that made the original request and is the target - * of this response. + * @param slave_port SlavePort that made the original request and + * is the target of this response. */ void updateResponse(const Packet *cpkt, const SlavePort& slave_port); + virtual void regStats(); + + protected: + + /** + * The underlying type for the bitmask we use for tracking. This + * limits the number of snooping ports supported per crossbar. For + * the moment it is an uint64_t to offer maximum + * scalability. However, it is possible to use e.g. a uint16_t or + * uint32_to slim down the footprint of the hash map (and + * ultimately improve the simulation performance). + */ + typedef uint64_t SnoopMask; + + /** + * Per cache line item tracking a bitmask of SlavePorts who have an + * outstanding request to this line (requested) or already share a + * cache line with this address (holder). + */ + struct SnoopItem { + SnoopMask requested; + SnoopMask holder; + }; + /** + * HashMap of SnoopItems indexed by line address + */ + typedef m5::hash_map SnoopFilterCache; + /** - * Simple factory methods for standard return values for lookupRequest + * Simple factory methods for standard return values. */ std::pair snoopAll(Cycles latency) const { @@ -207,24 +238,6 @@ class SnoopFilter : public SimObject { return std::make_pair(empty , latency); } - virtual void regStats(); - - protected: - typedef uint64_t SnoopMask; - /** - * Per cache line item tracking a bitmask of SlavePorts who have an - * outstanding request to this line (requested) or already share a cache line - * with this address (holder). - */ - struct SnoopItem { - SnoopMask requested; - SnoopMask holder; - }; - /** - * HashMap of SnoopItems indexed by line address - */ - typedef m5::hash_map SnoopFilterCache; - /** * Convert a single port to a corresponding, one-hot bitmask * @param port SlavePort that should be converted. @@ -244,6 +257,7 @@ class SnoopFilter : public SimObject { * Removes snoop filter items which have no requesters and no holders. */ void eraseIfNullEntry(SnoopFilterCache::iterator& sf_it); + /** Simple hash set of cached addresses. */ SnoopFilterCache cachedLocations; /** @@ -296,4 +310,5 @@ SnoopFilter::maskToPortList(SnoopMask port_mask) const res.push_back(p); return res; } + #endif // __MEM_SNOOP_FILTER_HH__ -- 2.30.2