<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:times new roman, new york, times, serif;font-size:12pt"><DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">Thanks,</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">I don;t have root access to the box. I will see if I can ask sys-admin to do it. I am running </DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">Linux snowwhite 2.6.18-8.el5 #1 SMP</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif"> </DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">DO you know if the broken yield got into this version ? </DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">FYI : the 'yield' people said it is not 'broken', it is in fact the 'right yield'.</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif"> </DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">tan</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif"><BR><BR> </DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: times new roman, new york, times, serif">----- Original Message ----<BR>From: Darius Buntinas <buntinas@mcs.anl.gov><BR>To: chong tan <chong_guan_tan@yahoo.com><BR>Cc: mpich-discuss@mcs.anl.gov<BR>Sent: Monday, December 17, 2007 10:50:12 AM<BR>Subject: Re: [MPICH] any way to ask nemesis to turn-off and turn of active polling ?<BR><BR><BR>Try setting the processor affinity for the "average" processes (map each <BR>one to its own processor). If you have a kernel with the "broken" <BR>sched_yield implementations, that may not help.<BR><BR>If you have a "broken" sched_yield implementation, you can try doing <BR>this as root:<BR> sysctl kernel.sched_compat_yield=1<BR>or<BR> echo "1">/proc/sys/kernel/sched_compat_yield<BR><BR>-d<BR><BR><BR>On 12/17/2007 11:35 AM, chong tan wrote:<BR>> Yes, in a very subtle way which has major impact on performance. I will <BR>> try to
decribe it a litle here:<BR>> <BR>> system has 32G, total image 35G. Load is a litle offbalance <BR>> mathematically, 4X dual core, running 5 processes.<BR>> 4 processes are the same size, each runs on a CPU. the last process is <BR>> very small, about10% of others, run<BR>> on a core of one of the CPU. SO 1 CPU runs 2 procs: average (P1)one and <BR>> light one (P2).<BR>> <BR>> All proc do first MPI comm in a fixed algorithmic point. The 'useful' <BR>> image is about 29G at that point, and should<BR>> fit into the physical memory. P2 get there in a heart beat, then <BR>> others., followed by P1 which took another 60+ minutes<BR>> to get there. If I combine P1 and P2 into 1 process, then I don;t no <BR>> see this extra delay.<BR>> <BR>> tan<BR>> <BR>> <BR>> <BR>> ----- Original Message ----<BR>> From: Darius Buntinas <<A
href="mailto:buntinas@mcs.anl.gov" ymailto="mailto:buntinas@mcs.anl.gov">buntinas@mcs.anl.gov</A>><BR>> To: chong tan <<A href="mailto:chong_guan_tan@yahoo.com" ymailto="mailto:chong_guan_tan@yahoo.com">chong_guan_tan@yahoo.com</A>><BR>> Cc: <A href="mailto:mpich-discuss@mcs.anl.gov" ymailto="mailto:mpich-discuss@mcs.anl.gov">mpich-discuss@mcs.anl.gov</A><BR>> Sent: Monday, December 17, 2007 8:02:17 AM<BR>> Subject: Re: [MPICH] any way to ask nemesis to turn-off and turn of <BR>> active polling ?<BR>> <BR>> <BR>> No, there's no way to do that. Even MPI_Barrier will do active polling.<BR>> <BR>> Are you having issues where an MPI process that is waiting in a blocking<BR>> call is taking CPU time away from other processes?<BR>> <BR>> -d<BR>> <BR>> On 12/14/2007 04:53 PM, chong tan wrote:<BR>> > My issue is like this :<BR>> > <BR>> > among all the processess,
some will get to the point of first MPI<BR>> > communication points faster than<BR>> > than other. Is there a way that I tell nemesis to start without doing<BR>> > active polling, and then turn<BR>> > on active polling with some function ?<BR>> > <BR>> > Or should I just use MPI_Barrier() on that ?<BR>> > <BR>> > thanks<BR>> > tan<BR>> > <BR>> ><BR>> > ------------------------------------------------------------------------<BR>> > Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try<BR>> > it now.<BR>> > <BR>> <<A href="http://us.rd.yahoo.com/evt=51733/*http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ" target=_blank>http://us.rd.yahoo.com/evt=51733/*http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ</A> <BR>> <BR>>
> ><BR>> <BR>> <BR>> ------------------------------------------------------------------------<BR>> Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try <BR>> it now. <BR>> <<A href="http://us.rd.yahoo.com/evt=51733/*http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ" target=_blank>http://us.rd.yahoo.com/evt=51733/*http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ</A> <BR>> ><BR></DIV>
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