Fix max advised memory percentage limit stat

Summary: D30981881 (facebook@1e0c331) broke stat cachelib.tao_follower_cache.mem.advised_size.pct (in TAO 169 release) which is now reported always as 0 - https://fburl.com/ods/wgohwnf8 This diff fixes that stat by getting its value from memory monitor, the source of truth.

Reviewed By: therealgymmy

Differential Revision: D31949077

fbshipit-source-id: fc0cf4d8ed40e949c1009160a97bf200fa92f8c9

Author: vrishal

cachelib/allocator/CacheAllocator-inl.h

@@ -3248,7 +3248,7 @@ CacheMemoryStats CacheAllocator<CacheTrait>::getCacheMemoryStats() const {
                           regularCacheSize,
                           compactCacheSize,
                           allocator_->getAdvisedMemorySize(),
-                          memMonitorMaxAdvisedPct_,
+                          memMonitor_ ? memMonitor_->getMaxAdvisePct() : 0,
                           allocator_->getUnreservedMemorySize(),
                           nvmCache_ ? nvmCache_->getSize() : 0,
                           memMonitor_ ? memMonitor_->getMemAvailableSize() : 0,

cachelib/allocator/CacheAllocator.h

@@ -1782,8 +1782,6 @@ class CacheAllocator : public CacheBase {
   // free memory monitor
   std::unique_ptr<MemoryMonitor> memMonitor_;
 
-  uint32_t memMonitorMaxAdvisedPct_{};
-
   // check whether a pool is a slabs pool
   std::array<bool, MemoryPoolManager::kMaxPools> isCompactCachePool_{};
 

cachelib/allocator/MemoryMonitor.h

@@ -201,7 +201,7 @@ class MemoryMonitor : public PeriodicWorker {
   unsigned int getNumSlabsReclaimed() const noexcept { return slabsReclaimed_; }
 
   // maximum percentage of regular cache memory that can be advised away.
-  double getMaxAdvisePct() const noexcept { return maxLimitPercent_; }
+  size_t getMaxAdvisePct() const noexcept { return maxLimitPercent_; }
 
   // amount of memory available on the host
   size_t getMemAvailableSize() const noexcept { return memAvailableSize_; }