[PATCH] parsers: when available, use a presized dictionary for the file foldmap

Augie Fackler raf at durin42.com
Wed Apr 15 17:35:46 CDT 2015


On Wed, Apr 15, 2015 at 02:38:52PM -0700, Siddharth Agarwal wrote:
> # HG changeset patch
> # User Siddharth Agarwal <sid0 at fb.com>
> # Date 1429133744 25200
> #      Wed Apr 15 14:35:44 2015 -0700
> # Node ID 8ca386e305d52af5e714126173bc15c884bf16fc
> # Parent  c560d8c687916cb70a6d54c2c9ddcb5c9e457be2
> parsers: when available, use a presized dictionary for the file foldmap

It might be interesting to expose a parsers.presizeddict() method to
our Python code as well.

Queued this, thanks.

>
> On a repo with over 300,000 files, this speeds up perffilefoldmap:
>
> before: wall 0.178421 comb 0.180000 user 0.160000 sys 0.020000 (best of 55)
> after:  wall 0.164462 comb 0.160000 user 0.140000 sys 0.020000 (best of 59)
>
> diff --git a/mercurial/parsers.c b/mercurial/parsers.c
> --- a/mercurial/parsers.c
> +++ b/mercurial/parsers.c
> @@ -205,7 +205,20 @@ static PyObject *make_file_foldmap(PyObj
>               goto quit;
>       }
>
> +#if PY_VERSION_HEX >= 0x02060000
> +	/* _PyDict_NewPresized expects a minused parameter, but it actually
> +        creates a dictionary that's the nearest power of two bigger than the
> +        parameter. For example, with the initial minused = 1000, the
> +        dictionary created has size 1024. Of course in a lot of cases that
> +        can be greater than the maximum load factor Python's dict object
> +        expects (= 2/3), so as soon as we cross the threshold we'll resize
> +        anyway. So create a dictionary that's 3/2 the size. Also add some
> +        more to deal with additions outside this function. */
> +	file_foldmap = _PyDict_NewPresized((PyDict_Size(dmap) / 5) * 8);
> +#else
>       file_foldmap = PyDict_New();
> +#endif
> +
>       if (file_foldmap == NULL)
>               goto quit;
>
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