From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shawn Pearce Subject: expanding pack idx fanout table Date: Mon, 8 Jul 2013 08:54:24 -0700 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: git X-From: git-owner@vger.kernel.org Mon Jul 08 17:54:50 2013 Return-path: Envelope-to: gcvg-git-2@plane.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1UwDm5-0003Y6-UP for gcvg-git-2@plane.gmane.org; Mon, 08 Jul 2013 17:54:50 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751696Ab3GHPyq (ORCPT ); Mon, 8 Jul 2013 11:54:46 -0400 Received: from mail-ie0-f179.google.com ([209.85.223.179]:64843 "EHLO mail-ie0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751547Ab3GHPyp (ORCPT ); Mon, 8 Jul 2013 11:54:45 -0400 Received: by mail-ie0-f179.google.com with SMTP id c10so9927052ieb.24 for ; Mon, 08 Jul 2013 08:54:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=spearce.org; s=google; h=mime-version:from:date:message-id:subject:to:content-type; bh=smJt6vQ7Fl+RNOg5dnQQ84UQkTe8ZwSSNp9qwsqy7I4=; b=TUPWKjACjUbAiWWN6crw8p7aPnPxJ2jf1WoFCOmoAVhHl4VbZuXbSvRz/GhBmag/aJ rJvHbEHgC0hWSHwVJMO63Rb/yhYIjjlgwPSCLXKsevv7H+5s53ZX28KrLekfJHnfAKEZ sX2279RiAP8EFl/zhrkN52TjgmfFkdyRP0SsM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:from:date:message-id:subject:to:content-type :x-gm-message-state; bh=smJt6vQ7Fl+RNOg5dnQQ84UQkTe8ZwSSNp9qwsqy7I4=; b=n5Q439opo3+z77D3DZsS/yw7/AoHFK8XdwujxuWsscao7h9Xr+I60+EhOAyOQzaIQP Q9Kvgy7nfkwAnT4o+52hL9WKR7pEZa2Oyrk+99prjkc+KVD53ReD+YXBZaX8VsYL2x+U SRfAIVsGQYoyHfvGkuJCyXQG5GKqErlSTL3sdAd7nM3e8oFJzMtq6tGzjtCixPgQ6gkN gTOZaZn/JIojZVKr1nk5Ta5Xqb9O0RsjuiaRr/rNTL7Jp+d9CmlV/1nj9ZZUt5GaVk4C YjkmSL1rfwxYFbesEG/8p4EtA8L/XfKgG+FsX0fWAHqWiIEnxePJLGB9k2wJzDAPIXoO 1wRg== X-Received: by 10.50.114.229 with SMTP id jj5mr8831853igb.36.1373298884938; Mon, 08 Jul 2013 08:54:44 -0700 (PDT) Received: by 10.64.143.200 with HTTP; Mon, 8 Jul 2013 08:54:24 -0700 (PDT) X-Gm-Message-State: ALoCoQnYW7XYTPMFPh6m+9LmroMY/qRPO1DbRB9SNRSOQ8Kh4aHZmIRN6h9xpst0bvg8zrvhw01d Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Has anyone studied the impact of converting the pack idx fanout table from 256 entries to 65536 entries? Back of the envelope estimates for 3.1M objects in linux.git suggests a 2^16 fanout table would decrease the number of binary search iterations from ~14 to ~6. The increased table costs an extra 255 KiB of disk. On a 70M idx file this is noise. I'm starting to wonder if increasing the fanout table once the object count is above a certain threshold is a reasonable optimization for larger repositories.