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Re: Tooltips GC overhead
From: |
David Kastrup |
Subject: |
Re: Tooltips GC overhead |
Date: |
Mon, 10 Aug 2015 19:44:23 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) |
Nix <address@hidden> writes:
> On 8 Aug 2015, David Kastrup uttered the following:
>
>> Stefan Monnier <address@hidden> writes:
>>
>>>> The cost you're trying to defend against here is a mispredicted branch
>>>
>>> No, I assume the branch would be properly predicted since it would
>>> always take the same path.
>>
>> If cons is encountered with high frequency. But of course, if it is
>> not, why bother in the first place?
>
> In that case I have no idea what you're trying to defend against. The
> cost of a single conditional and predicted branch is drowned in the
> overhead of the allocation that cons has to do anyway.
Cons cells are pooled, so in a long session the consolidated cost is
that of getting from the free list (cheap) and sweeping back into it
once a mark phase no longer visits the cell. Which would be the rule
rather than the exception for high-frequency consing.
> I'd be astonished if you could ever see any performance impact
> whatsoever.
Cons cells for Lisp should end up quite cheaper than arbitrary-size
allocations.
--
David Kastrup
- Re: Tooltips GC overhead, (continued)
- Re: Tooltips GC overhead, Paul Eggert, 2015/08/07
- Re: Tooltips GC overhead, Eli Zaretskii, 2015/08/07
- Re: Tooltips GC overhead, Nix, 2015/08/08
- Re: Tooltips GC overhead, Stefan Monnier, 2015/08/08
- Re: Tooltips GC overhead, David Kastrup, 2015/08/08
- Re: Tooltips GC overhead, Nix, 2015/08/10
- Re: Tooltips GC overhead,
David Kastrup <=