|From:||Ingo Molnar <mingo-AT-elte.hu>|
|To:||Nick Piggin <nickpiggin-AT-yahoo.com.au>|
|Subject:||Re: [patch 00/14] remap_file_pages protection support|
|Date:||Tue, 2 May 2006 13:24:09 +0200|
|Cc:||blaisorblade-AT-yahoo.it, Andrew Morton <akpm-AT-osdl.org>, linux-kernel-AT-vger.kernel.org, Linux Memory Management <linux-mm-AT-kvack.org>|
* Nick Piggin <email@example.com> wrote: > >Let's try get back to the good old days when people actually reported > >their bugs (togther will *real* numbers) to the mailing lists. That way, > >everybody gets to think about and discuss the problem. > > Speaking of which, let's see some numbers for UML -- performance and > memory. I don't doubt your claims, but I (and others) would be > interested to see. firstly, thanks for the review feedback! originally i tested this feature with some minimal amount of RAM simulated by UML 128MB or so. That's just 32 thousand pages, but still the improvement was massive: context-switch times in UML were cut in half or more. Process-creation times improved 10-fold. With this feature included I accidentally (for the first time ever!) confused an UML shell prompt with a real shell prompt. (before that UML was so slow [even in "skas mode"] that you'd immediately notice it by the shell's behavior) the 'have 1 vma instead of 32,000 vmas' thing is a really, really big plus. It makes UML comparable to Xen, in rough terms of basic VM design. Now imagine a somewhat larger setup - 16 GB RAM UML instance with 4 million vmas per UML process ... Frankly, without sys_remap_file_pages_prot() the UML design is still somewhat of a toy. Ingo
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