From: mquinson Date: Mon, 17 Dec 2007 15:12:58 +0000 (+0000) Subject: Document my lastest trick to increase the amount of started nodes in the simulator X-Git-Tag: v3.3~721 X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/commitdiff_plain/dcbf2427d14d935ac1cbc3981f4cc7a97d6e7cc3 Document my lastest trick to increase the amount of started nodes in the simulator git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/simgrid/simgrid/trunk@5128 48e7efb5-ca39-0410-a469-dd3cf9ba447f --- diff --git a/doc/FAQ.doc b/doc/FAQ.doc index 5856a6122f..a52ee0b265 100644 --- a/doc/FAQ.doc +++ b/doc/FAQ.doc @@ -680,7 +680,7 @@ of processes in your simulations. result in *fat* simulation hindering debugging. - It was really boring to write 25,000 entries in the deployment file, so I wrote a little script - examples/gras/tokenS/make_deployment.pl, which you may + examples/gras/mutual_exclusion/simple_token/make_deployment.pl, which you may want to adapt to your case. You could also think about hijacking the SURFXML parser (have look at \ref faq_flexml_bypassing). - The deployment file became quite big, so I had to do what is in @@ -690,10 +690,24 @@ of processes in your simulations. user don't get into trouble about this. You want to tune this size to increse the number of processes. This is the STACK_SIZE define in - src/xbt/context_private.h, which is 128kb by default. + src/xbt/xbt_ucontext.c, which is 128kb by default. Reduce this as much as you can, but be warned that if this value is too low, you'll get a segfault. The token ring example, which - is quite simple, runs with 40kb stacks. + is quite simple, runs with 40kb stacks. + - You may tweak the logs to reduce the stack size further. When + logging something, we try to build the string to display in a + char array on the stack. The size of this array is constant (and + equal to XBT_LOG_BUFF_SIZE, defined in include/xbt/log/h). If the + string is too large to fit this buffer, we move to a dynamically + sized buffer. In which case, we have to traverse one time the log + event arguments to compute the size we need for the buffer, + malloc it, and traverse the argument list again to do the actual + job.\n + The idea here is to move XBT_LOG_BUFF_SIZE to 1, forcing the logs + to use a dynamic array each time. This allows us to lower further + the stack size at the price of some performance loss...\n + This allowed me to run the reduce the stack size to ... 4k. Ie, + on my 1Gb laptop, I can run more than 250,000 processes! \subsubsection faq_MIA_batch_scheduler Is there a native support for batch schedulers in SimGrid?