memory statistics via an API ?
The +RTS -s runtime arguments give some useful details the memory usage of a program on exit. eg: 102,536 bytes allocated in the heap 2,620 bytes copied during GC 36,980 bytes maximum residency (1 sample(s)) 28,556 bytes maximum slop 1 MB total memory in use (0 MB lost due to fragmentation) Is there any means of obtaining this information at runtime, via some API? It would be useful for monitoring a long running server process. Tim ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: memory slop
On 14/04/2011, at 6:24 PM, Simon Marlow wrote: I made some changes to the storage manager in the runtime today, and fixed the slop problem with your program. Here it is after the changes: 14,928,031,040 bytes allocated in the heap 313,542,200 bytes copied during GC 18,044,096 bytes maximum residency (7 sample(s)) 294,256 bytes maximum slop 37 MB total memory in use (0 MB lost due to fragmentation) INITtime0.00s ( 0.00s elapsed) MUT time6.38s ( 6.39s elapsed) GC time1.26s ( 1.26s elapsed) EXITtime0.00s ( 0.00s elapsed) Total time7.64s ( 7.64s elapsed) I think this is with a different workload than the one you used above. Before the change I was getting 15,652,646,680 bytes allocated in the heap 312,402,760 bytes copied during GC 17,913,816 bytes maximum residency (9 sample(s)) 111,424,792 bytes maximum slop 142 MB total memory in use (0 MB lost due to fragmentation) INIT time0.00s ( 0.00s elapsed) MUT time8.01s ( 8.02s elapsed) GCtime 16.86s ( 16.89s elapsed) EXIT time0.00s ( 0.00s elapsed) Total time 24.88s ( 24.91s elapsed) (GHC 7.0.3 on x86-64/Linux) So, a pretty dramatic improvement. I'm validating the patch right now, it should be in 7.2.1. This looks really promising. Let me know when the patch is available, and I'll try it out on my real code. Thanks, Tim ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
memory slop (was: Using the GHC heap profiler)
On Mon, Mar 21, 2011 at 9:59 AM, I wrote: My question on the ghc heap profiler on stack overflow: http://stackoverflow.com/questions/5306717/how-should-i-interpret-the-output-of-the-ghc-heap-profiler remains unanswered :-( Perhaps that's not the best forum. Is there someone here prepared to explain how the memory usage in the heap profiler relates to the Live Bytes count shown in the garbage collection statistics? I've made a little progress on this. I've simplified my program down to a simple executable that loads a bunch of data into an in-memory map, and then writes it out again. I've added calls to `seq` to ensure that laziness is not causing excessing memory consumption. When I run this on my sample data set, it takes ~7 cpu seconds, and uses ~120 MB of vm An equivalent python script, takes ~2 secs and ~19MB of vm :-(. The code is below. I'm mostly concerned with the memory usage rather than performance at this stage. What is interesting, is that when I turn on garbage collection statistics (+RTS -s), I see this: 10,089,324,996 bytes allocated in the heap 201,018,116 bytes copied during GC 12,153,592 bytes maximum residency (8 sample(s)) 59,325,408 bytes maximum slop 114 MB total memory in use (1 MB lost due to fragmentation) Generation 0: 19226 collections, 0 parallel, 1.59s, 1.64selapsed Generation 1: 8 collections, 0 parallel, 0.04s, 0.04selapsed INIT time0.00s ( 0.00s elapsed) MUT time5.84s ( 5.96s elapsed) GCtime1.63s ( 1.68s elapsed) EXIT time0.00s ( 0.00s elapsed) Total time7.47s ( 7.64s elapsed) %GC time 21.8% (22.0% elapsed) Alloc rate1,726,702,840 bytes per MUT second Productivity 78.2% of total user, 76.5% of total elapsed This seems strange. The maximum residency of 12MB sounds about correct for my data. But what's with the 59MB of slop? According to the ghc docs: | The bytes maximum slop tells you the most space that is ever wasted | due to the way GHC allocates memory in blocks. Slop is memory at the | end of a block that was wasted. There's no way to control this; we | just like to see how much memory is being lost this way. There's this page also: http://hackage.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage/Slop but it doesn't really make things clearer for me. Is the slop number above likely to be a significant contribution to net memory usage? Are there any obvious reasons why the code below could be generating so much? The data file in question has 61k lines, and is 6MB in total. Thanks, Tim Map2.hs module Main where import qualified Data.Map as Map import qualified Data.ByteString.Char8 as BS import System.Environment import System.IO type MyMap = Map.Map BS.ByteString BS.ByteString foldLines :: (a - String - a) - a - Handle - IO a foldLines f a h = do eof - hIsEOF h if eof then (return a) else do l - hGetLine h let a' = f a l a' `seq` foldLines f a' h undumpFile :: FilePath - IO MyMap undumpFile path = do h - openFile path ReadMode m - foldLines addv Map.empty h hClose h return m where addv m = m addv m s = let (k,v) = readKV s in k `seq` v `seq` Map.insert k v m readKV s = let (ks,vs) = read s in (BS.pack ks, BS.pack vs) dump :: [(BS.ByteString,BS.ByteString)] - IO () dump vs = mapM_ putV vs where putV (k,v) = putStrLn (show (BS.unpack k, BS.unpack v)) main :: IO () main = do args - getArgs case args of [path] - do v - undumpFile path dump (Map.toList v) return () ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: memory slop
On 22/03/11 05:33, Daniel Fischer wrote: On Wednesday 23 March 2011 03:32:16, Tim Docker wrote: Is the slop number above likely to be a significant contribution to net memory usage? Yes, absolutely. Are there any obvious reasons why the code below could be generating so much? I suspect packing a lot of presumably relatively short ByteStrings would generate (the lion's share of) the slop. I'm not familiar with the internals, though, so I don't know where GHC would put a newPinnedByteArray# (which is where your ByteString contents is), what alignement requirements those have. Thanks, I'm aware that that the code could be optimised eg by sticking to bytestrings and avoiding Strings and read - there were just to make the example simple. I expected this would affect speed, though not memory usage. I'm a bit shocked at the amount of wasted memory here. The sample data file has ~61k key/value pair. Hence ~122k ByteStrings - as you point out many of these are very small (1500 of them are empty). Assuming it's the bytestring that are generating slop, I am seeing ~500 bytes on average per bytestring! Tim ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Re: memory slop
On 22/03/11 10:47, Brandon Moore wrote: It sounds like the space is allocated but unused pages. Unless you have messed with some kernel memory manager settings, unused virtual pages consume no physical RAM. You could confirm this by using ps to check how much RSS is actually used, compared to VSZ allocated (VSZ - RSS shouldn't include any actual data unless your system is actively swapping stuff to disk). If it is just unsued pages it's not a problem. Thanks. I've looked at this, and can confirm that the reported VSZ and RSS are almost the same (120MB and 116MB). I think this means that the observed memory usage is real. Tim ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
Using the GHC heap profiler
My question on the ghc heap profiler on stack overflow: http://stackoverflow.com/questions/5306717/how-should-i-interpret-the-output-of-the-ghc-heap-profiler remains unanswered :-( Perhaps that's not the best forum. Is there someone here prepared to explain how the memory usage in the heap profiler relates to the Live Bytes count shown in the garbage collection statistics? Many thanks, Tim ___ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
