GHC.Stats: Add info on amount of pinned memory

https://hackage.haskell.org/package/base-4.12.0.0/docs/GHC-Stats.html

GHC.Stats's GCDetails tells us, separately, the amount of

• total heap data (including large objects and compact data)
• large ojects
• compact data
• "Total amount of memory in use by the RTS" (gcdetails_mem_in_use_bytes)

There currently doesn't seem to be a way to get the amount of pinned memory in use.

So some questions:

• Is pinned memory accounted for in gcdetails_mem_in_use_bytes?
• If yes, is it pretty much that value minus gcdetails_live_bytes, or are there other memory uses that count to the latter?
• If I wanted to add the amount of pinned memory directly to GHC.Stats, where would I take that value from?

In general, my goal is to collect all easily (cheaply) collectable memory info so that I can add it to ekg.

Trac metadata

Trac field	Value
Version	8.6.2
Type	Task
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Runtime System
Test case
Differential revisions
BlockedBy
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Blocking
CC	nh2
Operating system
Architecture

changed milestone to %8.6.3

changed weight to 5

added RTS Ttask Trac import labels

To answer the questions:

• gcdetails_mem_in_use_bytes is simply mblocks_allocated * MBLOCK_SIZE.

Because pinned memory is also allocated via the block allocator gcdetails_mem_in_use_bytes includes pinned memory too.

• I don't understand this question.

• You'd need to compute this. In the GC once a pinned object block is filled we

only distinguish a pinned object block from a large object block in one place, to avoid scavenging pinned blocks. So there's no special accounting for pinned objects.

Perhaps you could implement something like calcTotalLargeObjectsW by checking if a BF_LARGE block is also BF_PINNED. If it is then add number of blocks to a counter. Then num_of_blocks * BLOCK_SIZE gives you the bytes.

Ticket retargeted after milestone closed

added Pnormal label

mentioned in merge request !1528 (closed)