Re: [PATCH v2 16/20] builtin/gc.c: guess the size of the revindex
Taylor Blau <me@ttaylorr.com> writes:
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> 'estimate_repack_memory()' takes into account the amount of memory
> required to load the reverse index in memory by multiplying the assumed
> number of objects by the size of the 'revindex_entry' struct.
>
> Prepare for hiding the definition of 'struct revindex_entry' by removing
> a 'sizeof()' of that type from outside of pack-revindex.c. Instead,
> guess that one off_t and one uint32_t are required per object. Strictly
> speaking, this is a worse guess than asking for 'sizeof(struct
> revindex_entry)' directly, since the true size of this struct is 16
> bytes with padding on the end of the struct in order to align the offset
> field.
Meaning that we under-estimate by 25%?
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> But, this is an approximation anyway, and it does remove a use of the
> 'struct revindex_entry' from outside of pack-revindex internals.
>
> Signed-off-by: Taylor Blau <me@ttaylorr.com>
> ---
> builtin/gc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/builtin/gc.c b/builtin/gc.c
> index 4c24f41852..c60811f212 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -301,7 +301,7 @@ static uint64_t estimate_repack_memory(struct packed_git *pack)
> /* and then obj_hash[], underestimated in fact */
> heap += sizeof(struct object *) * nr_objects;
> /* revindex is used also */
> - heap += sizeof(struct revindex_entry) * nr_objects;
> + heap += (sizeof(off_t) + sizeof(uint32_t)) * nr_objects;
> /*
> * read_sha1_file() (either at delta calculation phase, or
> * writing phase) also fills up the delta base cache
Junio C Hamano <gitster@pobox.com>