Hi,
I'll give --cache-remote a try later. However for now I'm facing some problems which definitely should be solved first...
The problem I'm having is that using GASNET_SPAWNF=L with UDP-conduit with more than one locale causes program to run _very_ slowly. For example, with one locale my test program did take 0.20 sec to run. With two locales it took 65 seconds. Same can be observed when running with GASNET_SPAWNF=S with UDP conduit on two separate machines. Using MPI conduit didn't make difference. Here's the environment variables I'm using
CHPL_HOME: /home/share/chapel/chapel-git
script location: /home/share/chapel/chapel-git/util
CHPL_HOST_PLATFORM: linux32
CHPL_HOST_COMPILER: gnu
CHPL_TARGET_PLATFORM: linux32
CHPL_TARGET_COMPILER: gnu
CHPL_TARGET_ARCH: unknown
CHPL_LOCALE_MODEL: flat
CHPL_COMM: gasnet
CHPL_COMM_SUBSTRATE: udp
CHPL_GASNET_SEGMENT: everything
CHPL_TASKS: fifo
CHPL_LAUNCHER: amudprun
CHPL_TIMERS: generic
CHPL_MEM: cstdlib
CHPL_MAKE: gmake
CHPL_ATOMICS: intrinsics
CHPL_NETWORK_ATOMICS: none
CHPL_GMP: none
CHPL_HWLOC: none
CHPL_REGEXP: none
CHPL_WIDE_POINTERS: struct
CHPL_LLVM: none
CHPL_AUX_FILESYS: none
script location: /home/share/chapel/chapel-git/util
CHPL_HOST_PLATFORM: linux32
CHPL_HOST_COMPILER: gnu
CHPL_TARGET_PLATFORM: linux32
CHPL_TARGET_COMPILER: gnu
CHPL_TARGET_ARCH: unknown
CHPL_LOCALE_MODEL: flat
CHPL_COMM: gasnet
CHPL_COMM_SUBSTRATE: udp
CHPL_GASNET_SEGMENT: everything
CHPL_TASKS: fifo
CHPL_LAUNCHER: amudprun
CHPL_TIMERS: generic
CHPL_MEM: cstdlib
CHPL_MAKE: gmake
CHPL_ATOMICS: intrinsics
CHPL_NETWORK_ATOMICS: none
CHPL_GMP: none
CHPL_HWLOC: none
CHPL_REGEXP: none
CHPL_WIDE_POINTERS: struct
CHPL_LLVM: none
CHPL_AUX_FILESYS: none
Any idea what could be causing this? As I said on some previous post my target environment is heterogeneous (all x86, though) commodity cluster with ethernet connections, so either UDP or MPI conduit is one I'd use..
18.02.2015, 23:41, "Greg Titus" <[email protected]>:
Hi John --
A little bit of follow-up to what Michael says here ...
The "nemesis" he refers to is the internal name of the particular Qthreads scheduler we use when CHPL_LOCALE_MODEL=flat. Our understanding is that the nemesis scheduler currently doesn't move qthreads (and by extension, Chapel tasks) from pthread to pthread, which would break the use of pthread local storage inside the remote caching implementation. But there are significant caveats here:Taken together, this basically says that although we haven't observed remote caching failures with qthreads, that shouldn't be taken as evidence that it definitely does work now or will work in the future.
- We use a different Qthreads scheduler when CHPL_LOCALE_MODEL=numa, and that one definitely does move qthreads (thus Chapel tasks) from pthread to pthread.
- We can't guarantee that we'll always use "nemesis" with the flat locale model.
- We can't guarantee that, even if we do keep using it, "nemesis" will continue to not move qthreads (thus Chapel tasks) from pthread to pthread.
greg
On 2/18/2015 2:31 PM, Michael Ferguson wrote:Hi -
One more thing about the --cache-remote feature, just to be clear and for future reference:
The remote caching depends on pthread local storage, and Chapel task movement among worker pthreads in Qthreads-based tasking could break it. So far we haven't seen this happen, but we cannot guarantee it won't. Symptoms of a failure could include silent wrong answers or segfaults, either of which could be solid or intermittent/sporadic.
I *think* that this problem won't come up with the nemesis qthreads scheduler, but we need to do some careful analysis before we can declare the --cache-remote feature safe to use with qthreads.
Cheers,
-michael
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