Re: [PATCH v2] index: add trace2 region for clear skip worktree

[Jeff Hostetler <git@jeffhostetler.com>]

On 10/27/22 8:46 PM, Anh Le via GitGitGadget wrote:
[...]
> diff --git a/sparse-index.c b/sparse-index.c
> index e4a54ce1943..dbf647949c1 100644
> --- a/sparse-index.c
> +++ b/sparse-index.c
> @@ -493,24 +493,38 @@ void clear_skip_worktree_from_present_files(struct index_state *istate)
>   	int dir_found = 1;
>   
>   	int i;
> +	int path_counts[2] = {0, 0};
> +	int restarted = 0;
>   
>   	if (!core_apply_sparse_checkout ||
>   	    sparse_expect_files_outside_of_patterns)
>   		return;
>   
> +	trace2_region_enter("index", "clear_skip_worktree_from_present_files", istate->repo);
>   restart:
>   	for (i = 0; i < istate->cache_nr; i++) {
>   		struct cache_entry *ce = istate->cache[i];
>   
> -		if (ce_skip_worktree(ce) &&
> -		    path_found(ce->name, &last_dirname, &dir_len, &dir_found)) {
> -			if (S_ISSPARSEDIR(ce->ce_mode)) {
> -				ensure_full_index(istate);
> -				goto restart;
> +		if (ce_skip_worktree(ce)) {
> +			path_counts[restarted]++;
> +			if (path_found(ce->name, &last_dirname, &dir_len, &dir_found)) {
> +				if (S_ISSPARSEDIR(ce->ce_mode)) {
> +					ensure_full_index(istate);
> +					restarted = 1;
> +					goto restart;
> +				}
> +				ce->ce_flags &= ~CE_SKIP_WORKTREE;
>   			}
> -			ce->ce_flags &= ~CE_SKIP_WORKTREE;
>   		}
>   	}
> +
> +	if (path_counts[0] > 0) {
> +		trace2_data_intmax("index", istate->repo, "clear_skip_worktree_from_present_files/path_count", path_counts[0]);
> +	}
> +	if (restarted) {
> +		trace2_data_intmax("index", istate->repo, "clear_skip_worktree_from_present_files/full_index/path_count", path_counts[1]);
> +	}
> +	trace2_region_leave("index", "clear_skip_worktree_from_present_files", istate->repo);
>   }

This looks good.  And I think it sets us up to later
answer some of our earlier perf questions after you
get some data.

For example, if the path_count[0] phase is expensive,
does the restart always need to restart the loop at i=0?
Granted, the `ensure_full_index()` may create a new cache-entry
array, so the value of `i` prior to the call may not correspond
to the same cell after the call at the `goto`, but we could
cache the strdup the pathname of cache[i] before the call and
do a find on the new cache[] afterwards to get the corresponding
i-prime value and let the restart start the loop on i-prime.
That's just an idea, but let's wait for the data to see if that
would be helpful.


Thanks!
Jeff