Try: remotecache: don't store allocator IDs

We can, as Matt so kindly reminds me, go get them from the pagemap. Since we need this value only when closing a ring, the read from over there is probably not very onerous. (We could also get the slab pointer from an object in the ring, but we need that whenever inserting into the cache, so it's probably more sensible to store that locally?)
microsoft · Jun 20, 2024 · b676148 · b676148
1 parent 97f8aea
commit b676148
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Showing 2 changed files with 8 additions and 14 deletions.
diff --git a/src/snmalloc/mem/localalloc.h b/src/snmalloc/mem/localalloc.h
@@ -286,7 +286,7 @@ namespace snmalloc
           address_cast(entry.get_slab_metadata()));
 #endif
         local_cache.remote_dealloc_cache.template dealloc<sizeof(CoreAlloc)>(
-          entry.get_slab_metadata(), entry.get_remote()->trunc_id(), p);
+          entry.get_slab_metadata(), p);
         post_remote_cache();
         return;
       }
@@ -679,7 +679,7 @@ namespace snmalloc
         if (local_cache.remote_dealloc_cache.reserve_space(entry))
         {
           local_cache.remote_dealloc_cache.template dealloc<sizeof(CoreAlloc)>(
-            entry.get_slab_metadata(), remote->trunc_id(), p_tame);
+            entry.get_slab_metadata(), p_tame);
 #  ifdef SNMALLOC_TRACING
           message<1024>(
             "Remote dealloc fast {} ({}, {})",

diff --git a/src/snmalloc/mem/remotecache.h b/src/snmalloc/mem/remotecache.h
@@ -24,7 +24,6 @@ namespace snmalloc
     std::array<freelist::Builder<false, true>, RINGS> open_builder;
     std::array<typename Config::PagemapEntry::SlabMetadata*, RINGS> open_meta =
       {nullptr};
-    std::array<RemoteAllocator::alloc_id_t, RINGS> open_target = {0};
 
     SNMALLOC_FAST_PATH size_t
     ring_set(typename Config::PagemapEntry::SlabMetadata* meta)
@@ -42,27 +41,25 @@ namespace snmalloc
         freelist::Object::key_root,
         open_meta[ix]->as_key_tweak());
 
-      forward(open_target[ix], rmsg);
+      auto& entry = Config::Backend::get_metaentry(address_cast(rmsg));
+
+      forward(entry.get_remote()->trunc_id(), rmsg);
 
       open_meta[ix] = nullptr;
     }
 
     SNMALLOC_FAST_PATH void init_one_pending(
-      size_t ix,
-      typename Config::PagemapEntry::SlabMetadata* meta,
-      RemoteAllocator::alloc_id_t id)
+      size_t ix, typename Config::PagemapEntry::SlabMetadata* meta)
     {
       open_builder[ix].init(
         0, freelist::Object::key_root, open_meta[ix]->as_key_tweak());
       open_meta[ix] = meta;
-      open_target[ix] = id;
     }
 
   public:
     template<typename Forward>
     SNMALLOC_FAST_PATH void dealloc(
       typename Config::PagemapEntry::SlabMetadata* meta,
-      RemoteAllocator::alloc_id_t target_id,
       freelist::HeadPtr r,
       Forward forward)
     {
@@ -102,7 +99,7 @@ namespace snmalloc
       {
         close_one_pending(forward, victim_ix);
       }
-      init_one_pending(victim_ix, meta, target_id);
+      init_one_pending(victim_ix, meta);
 
       open_builder[victim_ix].add(
         r, freelist::Object::key_root, meta->as_key_tweak());
@@ -197,17 +194,14 @@ namespace snmalloc
 
     template<size_t allocator_size>
     SNMALLOC_FAST_PATH void dealloc(
-      typename Config::PagemapEntry::SlabMetadata* meta,
-      RemoteAllocator::alloc_id_t target_id,
-      capptr::Alloc<void> p)
+      typename Config::PagemapEntry::SlabMetadata* meta, capptr::Alloc<void> p)
     {
       SNMALLOC_ASSERT(initialised);
 
       auto r = freelist::Object::make<capptr::bounds::AllocWild>(p);
 
       batching.dealloc(
         meta,
-        target_id,
         r,
         [this](
           RemoteAllocator::alloc_id_t target_id,