From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Geoffrey Irving" Subject: Re: [PATCH] Adding a cache of commit to patch-id pairs to speed up git-cherry Date: Mon, 2 Jun 2008 09:26:52 -0700 Message-ID: <7f9d599f0806020926j7ac9fb12jefa5a14fe5708226@mail.gmail.com> References: <7f9d599f0806012054y33b4fc10ha109aa4afbc7ca78@mail.gmail.com> <20080602064218.GA15144@sigill.intra.peff.net> <7f9d599f0806020735g30722893mb8efed41a6544ab5@mail.gmail.com> <7f9d599f0806020849g567461b2kecd65dbd35d3dc3b@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: "Jeff King" , "git@vger.kernel.org" To: "Johannes Schindelin" X-From: git-owner@vger.kernel.org Mon Jun 02 18:28:26 2008 Return-path: Envelope-to: gcvg-git-2@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by lo.gmane.org with esmtp (Exim 4.50) id 1K3Csy-0004hW-Bf for gcvg-git-2@gmane.org; Mon, 02 Jun 2008 18:27:52 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752657AbYFBQ0z (ORCPT ); Mon, 2 Jun 2008 12:26:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752649AbYFBQ0z (ORCPT ); Mon, 2 Jun 2008 12:26:55 -0400 Received: from py-out-1112.google.com ([64.233.166.181]:40690 "EHLO py-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752645AbYFBQ0y (ORCPT ); Mon, 2 Jun 2008 12:26:54 -0400 Received: by py-out-1112.google.com with SMTP id p76so474391pyb.10 for ; Mon, 02 Jun 2008 09:26:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; bh=tj6Zq67OCHgU5yU93AmbJVFw4CTexCmLBuIgyeYklfg=; b=uu0owhSbEvoH1O+daw682fWVyfvp+IytRKtqK3aRoLqlymPzP9aqJwiP3s4n+8eugmAun2amUzucCt25vTzr7xs9gNPMnykIofQ9/G6IJvYZgYv6F1ESwPG0Y1nyIrVpHjYh3agEullxl7qwz1n1fTKHx6B2PckKmaOPNc2ULKI= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=FLZR4TnSAaAAY2aEeNQgiaxd0qMUMsWaTPd6/k3gHVR0SexrvGtcTiOUobCDhGbAyG33+GPEg5GcuDxnUyXCj5QqTkmZx5zFn8JLJESYf+BeMYSUjm/+9ghkn7NOM8TaUCDkWAvk3SbyLMURc5wefD2fNCD4lggFB2BWXomBtWA= Received: by 10.141.33.21 with SMTP id l21mr5095601rvj.140.1212424012479; Mon, 02 Jun 2008 09:26:52 -0700 (PDT) Received: by 10.140.178.16 with HTTP; Mon, 2 Jun 2008 09:26:52 -0700 (PDT) In-Reply-To: Content-Disposition: inline X-Google-Sender-Auth: 74e2ce42ddebe83f Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On Mon, Jun 2, 2008 at 9:18 AM, Johannes Schindelin wrote: > Hi, > > On Mon, 2 Jun 2008, Geoffrey Irving wrote: > >> On Mon, Jun 2, 2008 at 8:37 AM, Johannes Schindelin >> wrote: >> >> > Another issue that just hit me: this cache is append-only, so if it >> > grows too large, you have no other option than to scratch and recreate >> > it. Maybe this needs porcelain support, too? (git gc?) >> >> If so, the correct operation is to go through the hash and remove >> entries that refer to commits that no longer exist. I can add this if >> you want. Hopefully somewhere along the way git-gc constructs an easy >> to traverse list of extant commits, and this will be straightforward. > > I don't know... if you have created a cached patch-id for every commit (by > mistake, for example) and do not need it anymore, it might make git-cherry > substantially faster to just scrap the cache. Well, ideally hash maps are O(1), but it could be a difference between a "compare 40 bytes" constant and a "read a 4k block into memory" constant, so in practice yes. Scrapping it entirely will also make the implementation much simpler. It seems a little sad to wipe all that effort each time, but regenerating the cache is likely to be less expensive than a git-gc, so it shouldn't change any amortized complexities. Geoffrey