Re: sharing memory map between processes (same parent)

On Wed, 30 Apr 2008 01:10:49 -0700 (PDT) David Schwartz <davids@xxxxxxxxxxxxx> wrote:
| On Apr 28, 10:00 pm, phil-news-nos...@xxxxxxxx wrote:
|
|> I wanted to overlap setting up the mapping with the work already taking place
|> in process B. Much of the work of setting up a mapping (like reading block
|> pointer records for the file) would not need to be repeated in such a transfer,
|> so the time delay in process B to merely accept the mapping from process A
|> means process B can get on to other things more quickly. On a slow machine,
|> it might not be any advantage. On a fast machine, maybe there would be.
|
| I'm betting you didn't measure, so this whole thing is premature
| optimization. In fact, it's premature pessimization since the cost of
| making the mapping is still paid, but added onto that is the cost of
| giving and receiving the mapping.

I plan to measure. But I plan to do that when I have enough alternate ideas
to measure against (if any).


| Transferring the mapping is going to be wildly expensive because it
| requires synchronization. I haven't measured either, but my gut tells
| me this would be a pessimization. It *might* make sense to have the
| other process warm the cache by 'stat'ing the file and maybe even
| reading it, but I doubt even that.

Well, I have concluded that the feature does not exist. I don't know that it
should exist. OTOH, I've seen many features that do exist which I cannot
explain why they would exist (but someone else might have a good explanation).
I really don't understand why the discussion is going down the path of trying
to say why such a feature is not practical to implement. Has someone asked
to have it implemented?

--
|WARNING: Due to extreme spam, I no longer see any articles originating from |
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| you will need to find a different place to post on Usenet. |
| Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |
.

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