Re: openMPI vs openMosix
"Wes Wagner" <[email protected]> Mon, 25 Jun 2007 08:45:58 -0700
| Newsgroups | gmane.linux.cluster.openmosix.general |
|---|---|
| Message-ID | <[email protected]> |
--===============0497338519== Content-Type: multipart/alternative; boundary="----=_Part_24669_25434783.1182786358437" ------=_Part_24669_25434783.1182786358437 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Moshe is entirely correct. Without some type of extremely high powered crossbar style interconnect between machines, shared memory amongst nodes becomes a huge bottleneck and very slow. Even with fast networks and system buses, the latency is huge. You are taking what is a normal latency that is measured in nanoseconds and turning it into a latency that is measured in milliseconds. That is 3 orders of magnitude! :) If your system really requires fast shared memory, then you are looking at having to pony up the big buck for a large SMP environment (IBM,Sun,HP,Unisys, etc.) If you can engineer your application to run in more of a "shared-nothing" capacity, your ability to scale goes up dramatically. -Wes On 6/25/07, Moshe Bar <[email protected]> wrote: > > we used to have it. Shared memory without hardware support very > severely limits the types of apps that will actually scale. Even sgi > in their altix machines (which are essentiallys shared memory > machines) have very limited scalability for a lot of apps, if not > most. > > M > > > On 6/25/07, Lars O. Grobe <[email protected]> wrote: > > I guess the key point is - no shared memory in openmosix. > > > > > ------------------------------------------------------------------------- > > This SF.net email is sponsored by DB2 Express > > Download DB2 Express C - the FREE version of DB2 express and take > > control of your XML. No limits. Just data. Click to get it now. > > http://sourceforge.net/powerbar/db2/ > > _______________________________________________ > > openMosix-general mailing list > > openMosix-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org > > https://lists.sourceforge.net/lists/listinfo/openmosix-general > > > > > > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by DB2 Express > Download DB2 Express C - the FREE version of DB2 express and take > control of your XML. No limits. Just data. Click to get it now. > http://sourceforge.net/powerbar/db2/ > _______________________________________________ > openMosix-general mailing list > openMosix-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org > https://lists.sourceforge.net/lists/listinfo/openmosix-general > -- Wes Wagner Join a libertarian network of person-to-person lending on Prosper: http://www.prosper.com/groups/group_home.aspx?group_short_name=freelibertarians&referrer=AiriusTorpora&utm_source=referrer-AiriusTorpora&utm_medium=referral-link&utm_content=join_my_group-160x33&utm_campaign=referrals-group ------=_Part_24669_25434783.1182786358437 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Moshe is entirely correct. Without some type of extremely high powered crossbar style interconnect between machines, shared memory amongst nodes becomes a huge bottleneck and very slow. Even with fast networks and system buses, the latency is huge. You are taking what is a normal latency that is measured in nanoseconds and turning it into a latency that is measured in milliseconds. That is 3 orders of magnitude! :) <br><br>If your system really requires fast shared memory, then you are looking at having to pony up the big buck for a large SMP environment (IBM,Sun,HP,Unisys, etc.) <br><br>If you can engineer your application to run in more of a "shared-nothing" capacity, your ability to scale goes up dramatically. <br><br>-Wes<br><br><br><div><span class="gmail_quote">On 6/25/07, <b class="gmail_sendername">Moshe Bar</b> <<a href="mailto:[email protected]">[email protected]</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> we used to have it. Shared memory without hardware support very<br>severely limits the types of apps that will actually scale. Even sgi<br>in their altix machines (which are essentiallys shared memory<br>machines) have very limited scalability for a lot of apps, if not <br>most.<br><br>M<br><br><br>On 6/25/07, Lars O. Grobe <<a href="mailto:[email protected]">[email protected]</a>> wrote:<br>> I guess the key point is - no shared memory in openmosix.<br>><br>> ------------------------------------------------------------------------- <br>> This SF.net email is sponsored by DB2 Express<br>> Download DB2 Express C - the FREE version of DB2 express and take<br>> control of your XML. No limits. Just data. Click to get it now.<br>> <a href="http://sourceforge.net/powerbar/db2/"> http://sourceforge.net/powerbar/db2/</a><br>> _______________________________________________<br>> openMosix-general mailing list<br>> <a href="mailto:openMosix-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org">openMosix-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org </a><br>> <a href="https://lists.sourceforge.net/lists/listinfo/openmosix-general">https://lists.sourceforge.net/lists/listinfo/openmosix-general</a><br>><br>><br>><br><br>------------------------------------------------------------------------- <br>This SF.net email is sponsored by DB2 Express<br>Download DB2 Express C - the FREE version of DB2 express and take<br>control of your XML. No limits. Just data. Click to get it now.<br><a href="http://sourceforge.net/powerbar/db2/"> http://sourceforge.net/powerbar/db2/</a><br>_______________________________________________<br>openMosix-general mailing list<br><a href="mailto:openMosix-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org">openMosix-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org </a><br><a href="https://lists.sourceforge.net/lists/listinfo/openmosix-general">https://lists.sourceforge.net/lists/listinfo/openmosix-general</a><br></blockquote></div><br><br clear="all"><br>-- <br>Wes Wagner<br><br>Join a libertarian network of person-to-person lending on Prosper: <br> <br><a href="http://www.prosper.com/groups/group_home.aspx?group_short_name=freelibertarians&referrer=AiriusTorpora&utm_source=referrer-AiriusTorpora&utm_medium=referral-link&utm_content=join_my_group-160x33&utm_campaign=referrals-group"> http://www.prosper.com/groups/group_home.aspx?group_short_name=freelibertarians&referrer=AiriusTorpora&utm_source=referrer-AiriusTorpora&utm_medium=referral-link&utm_content=join_my_group-160x33&utm_campaign=referrals-group </a> ------=_Part_24669_25434783.1182786358437-- --===============0497338519== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ --===============0497338519== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ openMosix-general mailing list openMosix-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org https://lists.sourceforge.net/lists/listinfo/openmosix-general --===============0497338519==--