From: Junio C Hamano Date: Tue, 18 Feb 2014 20:59:43 GMT Subject: Re: git gc --aggressive led to about 40 times slower "git log --raw" Message-ID: In-Reply-To: <20140218155842.GA7855@google.com> Jonathan Nieder writes: > David Kastrup wrote: >> Duy Nguyen writes: > >>> Likely because --aggressive passes --depth=250 to pack-objects. Long >>> delta chains could reduce pack size and increase I/O as well as zlib >>> processing signficantly. > [...] >> Compression should reduce rather than increase the total amount of >> reads. > > --depth=250 means to allow chains of "To get this object, first > inflate this object, then apply this delta" of length 250. > > That's absurdly long, and doesn't even help compression much in > practice (many short chains referring to the same objects tends to > work fine). We probably shouldn't make --aggressive do that. > Something like --depth=10 would make more sense. Yes, my thinking indeed. I didn't know --agressive was so aggressive myself, as I personally never use it. "git repack -a -d -f --depth=32 window=4000" is what I often use, but I suspect most people would not be patient enough for that 4k window. Let's do something like this first and then later make --depth configurable just like --width, perhaps? For "aggressive", I think the default width (hardcoded to 250 but configurable) is a bit too narrow. builtin/gc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/builtin/gc.c b/builtin/gc.c index 6be6c8d..0d010f0 100644 --- a/builtin/gc.c +++ b/builtin/gc.c @@ -204,7 +204,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix) if (aggressive) { argv_array_push(&repack, "-f"); - argv_array_push(&repack, "--depth=250"); + argv_array_push(&repack, "--depth=20"); if (aggressive_window > 0) argv_array_pushf(&repack, "--window=%d", aggressive_window); }