a promising approach to debugging remote promises thurs/03-leske-iwst2… · a promising approach...
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A PROMISING APPROACH TO DEBUGGING REMOTE
PROMISES
2016 Max Leske Andrei Chiș Oscar Nierstrasz
DISCLAIMER
MOTIVATION
request file list
display file list
receive file list
request file list
display file listreceive file list
request file list
PROMISE
receive file list
use
use
continue
fileListPromise := [ self getFileList ] promise.
fileListPromise value.…
request file list
what happened?
stack tracestack trace
descriptiondescription
NULLNULL
what happened?
exception object
IDEA
1sender
receiver1
Object
Context
CompiledMethod1method
Process
suspendedContext1
sender
nilsender
Process
suspendedContext
sender
nil
sender
Process1
suspendedContext
sender
nilsender
Process2
suspendedContext
sender
Process1+2
suspendedContext
sendersender
sender
sendernil
DEMO
MEMORY
object header: 64 bits
2
pinned / immutable
slots
8
identity hash
22
format
5
class index
22
unused
2
garbage collection
3
object header
extended header
slot 0 slot 1
slot 2 …
object
object header
Context
method
closureOrNil
stackp
receiver
sender pc
16 / 56 variable slots
no extended header required
96 / 256 bytes per instance
∑ ≪ 100 000 ~ 1000
small contexts: 96 kB
large contexts: 256 kB* 2 (reification)
small contexts: 192 kB
large contexts: 512 kB
estimated upper bounds
memory consumption of contexts:
object graph (simplified)
garbage collector
partially collected
garbage collector
not collected
copy
memory consumption of object graph: ?
PERFORMANCE
fileListPromise := [ self getFileList ] promise.
fileListPromise value.…
copy process full copy
reify contexts
copying stack of 100 000 frames
0 MS
125 MS
250 MS
375 MS
500 MS
SMALL CONTEXTS LARGE CONTEXTS SMALL CONTEXTS LARGE CONTEXTS
with GC without GC
performance:
REMOTE COMMUNICATION
protocol?
SeamlessSeamless
DEBUGGING
serialised process
local copy of process
proxies
THREADSpromises
events
asynchronous messages (actors)
asynchronous network requests
request file list
what happened?
copy process full copy
reify contexts
Process1+2
suspendedContext
sender
nil
sender
sender
sender
sender
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