Hi, for 32bit application you can never allocate whole 4GB as some memory has to be reserved for kernel. The usual split is 2/2, sometimes 3/1. Plus, the actual code must be somewhere in the memory as well as the stack. Usually the real limit for 32bit application is somewhere like 1.8GB for heap. With 3/1 split you can have one more gig, but for linux that would require a 3/1 support in the kernel. If I'm not mistaken most stock kernels come with 2/2 split. Jan On 28/06/13 23:02, Sven Van Caekenberghe wrote:
Hi,
I wrote a little test to explore the heap size limits of the current Pharo image+VM combination. I did some tests on a 8GB 64-bit Linux machine and the basic conclusion is that using a standard 1GB heap size you can allocate and GC with close to 1GB of actual data. I think that is pretty good news. The machine has 4 effective cores, so could easily run 4 busy images like that.
Pushing the limits further, things get weird, up to the point of crashing. Sadly 2, 3 or 4 GB heap size, which should be theoretically possible, fail, thus limiting the amount of data that can be allocated and used.
Anyway, my goal is to start the debate around this topic ;-)
Here is the test script:
t3@coolermaster:smalltalk$ cat memtest.st
NonInteractiveTranscript stdout install.
!
Transcript show: 'memtest.st'; cr. Smalltalk garbageCollect. Transcript show: SmalltalkImage current vm statisticsReport; cr.
!
| count size data timeToRun | count := Smalltalk commandLine arguments first asInteger. size := Smalltalk commandLine arguments second asInteger. Transcript show: ('allocating: {1} times {2} bytes' format: { count. size }); cr. timeToRun := [ data := Array new: count streamContents: [ :out | count timesRepeat: [ out nextPut: (ByteArray new: size) ] ]. ] timeToRun. Transcript show: ('allocated: {1}' format: { (data collect: #size) sum humanReadableSIByteSize }); cr. Transcript show: ('time to run {1}' format: { Duration milliSeconds: timeToRun }); cr. Transcript show: '3 times GC'; cr. timeToRun := [ 3 timesRepeat: [ Smalltalk garbageCollect ] ] timeToRun. Transcript show: ('time to run {1}' format: { Duration milliSeconds: timeToRun }); cr. Transcript show: SmalltalkImage current vm statisticsReport; cr.
!
SmalltalkImage current quitPrimitive.
And here is a normal result running get.pharo.org/20+vm
$ ./pharo Pharo.image memtest.st 512 1024000
memtest.st uptime 0h0m0s memory 25,076,708 bytes old 19,213,624 bytes (76.60000000000001%) young 5,384 bytes (0.0%) used 19,219,008 bytes (76.60000000000001%) free 5,857,700 bytes (23.400000000000002%) GCs 10 (12ms between GCs) full 1 totalling 30ms (25.0% uptime), avg 30.0ms incr 9 totalling 6ms (5.0% uptime), avg 0.7000000000000001ms tenures 0
allocating: 512 times 1024000 bytes allocated: 524.29 MB time to run 0:00:00:02.852 3 times GC time to run 0:00:00:00.196 uptime 0h0m3s memory 546,746,364 bytes old 543,520,476 bytes (99.4%) young 7,184 bytes (0.0%) used 543,527,660 bytes (99.4%) free 3,218,704 bytes (0.6000000000000001%) GCs 356 (9ms between GCs) full 89 totalling 2,743ms (86.4% uptime), avg 30.8ms incr 267 totalling 223ms (7.0% uptime), avg 0.8ms tenures 0 Since last view 346 (9ms between GCs) uptime 3.1s full 88 totalling 2,713ms (88.80000000000001% uptime), avg 30.8ms incr 258 totalling 217ms (7.1000000000000005% uptime), avg 0.8ms tenures 0
It takes about 2.5s to allocate about 512Mb. A GC then takes 30ms.
You can play a bit with the 2 parameters to generate different datasets.
Not changing any VM parameters, you can successfully do something like
$ ./pharo Pharo.image memtest.st 1000 1024000
or
$ ./pharo Pharo.image memtest.st 1024000 1000
thus allocating about 1GB.
Playing with -mmap gives some weird results and unexpected slowness as well. Consider (the default -mmap is 1024m):
$ ./pharo -mmap 1280m Pharo.image memtest.st 500 1024000
memtest.st uptime 0h0m0s memory 25,076,716 bytes old 19,213,480 bytes (76.60000000000001%) young 5,384 bytes (0.0%) used 19,218,864 bytes (76.60000000000001%) free 5,857,852 bytes (23.400000000000002%) GCs 12 (13ms between GCs) full 2 totalling 56ms (37.1% uptime), avg 28.0ms incr 10 totalling 6ms (4.0% uptime), avg 0.6000000000000001ms tenures 0
allocating: 500 times 1024000 bytes allocated: 512.00 MB time to run 0:00:00:13.66 3 times GC time to run 0:00:00:00.192 uptime 0h0m14s memory 533,946,384 bytes old 531,232,232 bytes (99.5%) young 7,644 bytes (0.0%) used 531,239,876 bytes (99.5%) free 2,706,508 bytes (0.5%) GCs 1,011 (14ms between GCs) full 501 totalling 13,819ms (98.7% uptime), avg 27.6ms incr 510 totalling 35ms (0.2% uptime), avg 0.1ms tenures 0 Since last view 999 (14ms between GCs) uptime 13.9s full 499 totalling 13,763ms (99.30000000000001% uptime), avg 27.6ms incr 500 totalling 29ms (0.2% uptime), avg 0.1ms tenures 0
So increasing the heap from 1024 Mb to 1280 Mb slows the allocation down to 14s.
Increasing the heap size to 1792 Mb gives the following result:
t3@coolermaster:smalltalk$ ./pharo -mmap 1792m Pharo.image memtest.st 1280 1048576
memtest.st uptime 0h0m0s memory 25,076,708 bytes old 19,213,592 bytes (76.60000000000001%) young 5,384 bytes (0.0%) used 19,218,976 bytes (76.60000000000001%) free 5,857,732 bytes (23.400000000000002%) GCs 12 (12ms between GCs) full 2 totalling 55ms (37.9% uptime), avg 27.5ms incr 10 totalling 6ms (4.1000000000000005% uptime), avg 0.6000000000000001ms tenures 0
allocating: 1280 times 1048576 bytes allocated: 1.34 GB time to run 0:00:00:35.258 3 times GC time to run 0:00:00:00.37 uptime 0h0m35s memory -783,340,292 bytes old -786,061,544 bytes (100.30000000000001%) young 7,460 bytes (0.0%) used -786,054,084 bytes (100.30000000000001%) free 2,713,792 bytes (-0.30000000000000004%) GCs 2,572 (14ms between GCs) full 1281 totalling 35,444ms (99.10000000000001% uptime), avg 27.700000000000003ms incr 1291 totalling 93ms (0.30000000000000004% uptime), avg 0.1ms tenures 0 Since last view 2,560 (14ms between GCs) uptime 35.6s full 1279 totalling 35,389ms (99.30000000000001% uptime), avg 27.700000000000003ms incr 1281 totalling 87ms (0.2% uptime), avg 0.1ms tenures 0
The allocation takes a lot longer, but the GC times are stable.
I suspect that negative reporting has to do with SmallInteger limitations, but the question is if it is only a cosmetic problem or not.
Again, I am not complaining, just exploring/wondering.
Sven