[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

David Kastrup

reply via email to

[Prev in Thread] Current Thread [Next in Thread]