[compiler-rt] [scudo] Add time of last page release to getStats() (PR #164004)

[via llvm-commits]

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@@ -1146,17 +1148,24 @@ void SizeClassAllocator64<Config>::getStats(ScopedString *Str, uptr ClassId,
         BytesInFreeList - Region->ReleaseInfo.BytesInFreeListAtLastCheckpoint;
   }
   const uptr TotalChunks = Region->MemMapInfo.AllocatedUser / BlockSize;
+  const u64 CurTimeNs = getMonotonicTime();
+  const u64 DiffSinceLastReleaseNs =
+      CurTimeNs - Region->ReleaseInfo.LastReleaseAtNs;
+  const u64 LastReleaseSecAgo = DiffSinceLastReleaseNs / 1000000000;
+  const u64 LastReleaseMsAgo = (DiffSinceLastReleaseNs % 1000000000) / 1000000;
+
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ChiaHungDuan wrote:

I have a new thought about this, given that we have `ReleaseToOsInterval`, can we print something like `> ReleaseToOsInterval` `< ReleaseToOsInterval`?

If we hit the threshold to do the page release but it's too close (diff time less than ReleaseToOsInterval) then we will skip the page release. Thus I think longer/shorter than the interval gives us enough information about why the pages aren't released.

Sorry I didn't think about this while came up with the work

https://github.com/llvm/llvm-project/pull/164004