[Intel-gfx] [PATCH 2/2] dim: Try to gc the rr-cache

[Sean Paul]

On Wed, Jul 12, 2017 at 02:12:24PM +0200, Daniel Vetter wrote:
> The problem is that we have a distributed cache - every committer has
> a copy. Which means even just a slight clock skew will make sure that
> a naive gc algorithm results in lots of thrashing around.
> 
> To fix this add a huge hysteresis: Only add files newer than 1 day,
> and only remove them when older than 60 days. As long as people have
> reasonable accurate clocks on their machines this should work.
> 
> A different problem is that we can't use filesystem timestamps (and
> hence can't use git rerere gc): When someone comes back from vacations
> and updates git rerere, all the files will have current timestamps,
> even when they've been pushed out weeks ago. To fix that, use the git
> log to judge old files to remove. Also, remove old files before adding
> new ones, to avoid confusion.
> 
> Also, we need to teach the cp -r to preserve timestamps, otherwise
> this won't work.
> 
> v2: Use git log to remove old files.
> 
> v3: Remove the debug uncommenting (Sean).
> 
> v4: Split out code movement and explain better what's going on (Jani).

Yeah, much easier to digest with the split.

Reviewed-by: Sean Paul <seanpaul at chromium.org>

> 
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  dim | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/dim b/dim
> index b788edd29653..79d616cbf354 100755
> --- a/dim
> +++ b/dim
> @@ -513,9 +513,15 @@ function commit_rerere_cache
>  
>  		git pull >& /dev/null
>  		rm $(rr_cache_dir)/rr-cache -Rf &> /dev/null || true
> -		cp $(rr_cache_dir)/* rr-cache -r
> +		cp $(rr_cache_dir)/* rr-cache -r --preserve=timestamps
>  		git add ./*.patch >& /dev/null || true
> -		git add rr-cache/* > /dev/null
> +		for file  in $(git ls-files); do
> +			if ! git log --since="60 days ago" --name-only -- $file | grep $file &> /dev/null; then
> +				git rm $file &> /dev/null
> +				echo deleting $file
> +			fi
> +		done
> +		find rr-cache/ -ctime -1 -type f -print0 | xargs -0 git add > /dev/null
>  		git rm rr-cache/rr-cache &> /dev/null || true
>  		if git commit -m "$time: $integration_branch rerere cache update" >& /dev/null; then
>  			echo -n "New commit. "
> -- 
> 2.13.2
> 
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-- 
Sean Paul, Software Engineer, Google / Chromium OS