Messages in this thread | | | Date | Fri, 25 Oct 2013 04:28:27 -0700 (PDT) | From | David Lang <> | Subject | Re: Disabling in-memory write cache for x86-64 in Linux II |
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On Fri, 25 Oct 2013, Linus Torvalds wrote:
> On Fri, Oct 25, 2013 at 9:30 AM, Artem S. Tashkinov <t.artem@lycos.com> wrote: >> >> My feeling is that vm.dirty_ratio/vm.dirty_background_ratio should _not_ be >> percentage based, 'cause for PCs/servers with a lot of memory (say 64GB or >> more) this value becomes unrealistic (13GB) and I've already had some >> unpleasant effects due to it. > > Right. The percentage notion really goes back to the days when we > typically had 8-64 *megabytes* of memory So if you had a 8MB machine > you wouldn't want to have more than one megabyte of dirty data, but if > you were "Mr Moneybags" and could afford 64MB, you might want to have > up to 8MB dirty!! > > Things have changed. > > So I would suggest we change the defaults. Or pwehaps make the rule be > that "the ratio numbers are 'ratio of memory up to 1GB'", to make the > semantics similar across 32-bit HIGHMEM machines and 64-bit machines.
If you go this direction, allow ratios larger than 100%, some people may be willing to have huge amounts of dirty data on large memory machines (if the load is extremely bursty, they don't have other needs for I/O, or they have a very fast storage system, as a few examples)
David Lang
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