Re: [BENCHMARK] 12% improvement in fork load from mm3 to mm4

From: Andrew Morton (
Date: Mon Jun 09 2003 - 17:09:05 EST wrote:
> > autoconf build test creates about 1.2 million processes in
> > 35 minutes. On quad xeon, there was an improvement of
> > ~ 12% between 2.5.70-mm3 and 2.5.70-mm4.
> >
> > Avg of 3 runs
> > 2.5.70-mm3 829.0
> > 2.5.70-mm4 737.9
> profile shows the biggest change is in do_page_fault.

Well that's amusing. In mm4 I replaced the patch which runs
remap_file_pages() against all prot_exec mappings with a patch which just
prefaults those mappings into pagecache.

The difference _should_ be that in mm3, all pte's are set up at mmap time.
So -mm4 should have more pagefaults, not less.

Something fishy is going on there. Makes one wonder if remap_file_pages()
is successfully avoiding the minor fault.

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