From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fout-a1-smtp.messagingengine.com (fout-a1-smtp.messagingengine.com [103.168.172.144]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1373713D51E for ; Wed, 4 Dec 2024 05:02:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=103.168.172.144 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733288539; cv=none; b=P87L66wKjHA3KN0zGuRXlOW1ljeiMKzRbjAR0C8OHRvM9nS/gRnOIRPaCJP2WC0LcpgMzZDAgp0n9PjVXff+s8SGIx71KDUciWOWK3kJQYARFpvTPqjPtBAD9YR9Go1UTeaPlJaHKCJdc2zgpwcZ8BDqDVWZTCxWN5FlROeMQRA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733288539; c=relaxed/simple; bh=u/xA/lXoXM4aX9odX6weUUgrU596NpbfPYKpw3ewqV4=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=ayUhzJ6wc+btF+hygJxWVH/b1Y6qygSjmske5sqtQqmcfkW2ELkgFfOIEUVsUfGbjBCow0DPKSB9pX9msS2Dt34qP2uCxUHv0g9DSpn9lNg/ug+kGRCdddB5ia8c0OTHQY8ZlDeSDLK7Rcb5XnlEMdBC2vF6lOioOC2ZFow6BNA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=pobox.com; spf=pass smtp.mailfrom=pobox.com; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b=BCIy7B1/; arc=none smtp.client-ip=103.168.172.144 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=pobox.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pobox.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=messagingengine.com header.i=@messagingengine.com header.b="BCIy7B1/" Received: from phl-compute-02.internal (phl-compute-02.phl.internal [10.202.2.42]) by mailfout.phl.internal (Postfix) with ESMTP id 337FE13802D7; Wed, 4 Dec 2024 00:02:16 -0500 (EST) Received: from phl-frontend-01 ([10.202.2.160]) by phl-compute-02.internal (MEProxy); Wed, 04 Dec 2024 00:02:16 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-type:content-type:date:date :feedback-id:feedback-id:from:from:in-reply-to:in-reply-to :message-id:mime-version:references:reply-to:subject:subject:to :to:x-me-proxy:x-me-sender:x-me-sender:x-sasl-enc; s=fm1; t= 1733288536; x=1733374936; bh=55rQN0hTOIIgoa6tqCbs9ZVoRcgS5tYcKa6 bbpbXHUs=; b=BCIy7B1/gVILN0mqSUxH8SBddXrk96ewzqxSF59SPKosumBhE7k UcetAil8g4p8y7DVu482ZndlwQtexXYLpCTqZ6q+pb+K+BNPJi8AA+5sqTXSFiIT Ol6AJtsIyfL5Z97NgpEvJ6j9/eCqThiXKHIRfbeUp6tiVK1zk2OzNsiqDmmOJKGZ nnMyhCRvXwTjicdk0gW70F1BTPL1GvvUtte4EmbQJssHn86l2yyPqHLmJN+VzFrE J3zhF1JB/sAmA0dcWAMTopMwQmnnSWnKz7Bkwb/Hm0EUD7zLfyMMw11y2zvFwLWc F4+wp/eFFrla+ZAW7WUNFYUk2IUDE/TsSHg== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgeefuddrieeggdejhecutefuodetggdotefrodftvf curfhrohhfihhlvgemucfhrghsthforghilhdpggftfghnshhusghstghrihgsvgdpuffr tefokffrpgfnqfghnecuuegrihhlohhuthemuceftddtnecusecvtfgvtghiphhivghnth hsucdlqddutddtmdenucfjughrpefhvfevufgjfhffkfgfgggtsehttdertddtredtnecu hfhrohhmpefluhhnihhoucevucfjrghmrghnohcuoehgihhtshhtvghrsehpohgsohigrd gtohhmqeenucggtffrrghtthgvrhhnpeefveetteejheeugeffledvteeiveffueefjeel ueffteeigffgfedthfefieegieenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmh epmhgrihhlfhhrohhmpehgihhtshhtvghrsehpohgsohigrdgtohhmpdhnsggprhgtphht thhopeduuddpmhhouggvpehsmhhtphhouhhtpdhrtghpthhtohepshhtohhlvggvsehgmh grihhlrdgtohhmpdhrtghpthhtohepghhithhgihhtghgrughgvghtsehgmhgrihhlrdgt ohhmpdhrtghpthhtohepghhithesvhhgvghrrdhkvghrnhgvlhdrohhrghdprhgtphhtth hopehjohhhrghnnhgvshdrshgthhhinhguvghlihhnsehgmhigrdguvgdprhgtphhtthho pehpvghffhesphgvfhhfrdhnvghtpdhrtghpthhtohepphhssehpkhhsrdhimhdprhgtph htthhopehmvgesthhtrgihlhhorhhrrdgtohhmpdhrtghpthhtohepjhhohhhntggrihek ieesghhmrghilhdrtghomhdprhgtphhtthhopehnvgifrhgvnhesghhmrghilhdrtghomh X-ME-Proxy: Feedback-ID: if26b431b:Fastmail Received: by mail.messagingengine.com (Postfix) with ESMTPA; Wed, 4 Dec 2024 00:02:15 -0500 (EST) From: Junio C Hamano To: Derrick Stolee Cc: Derrick Stolee via GitGitGadget , git@vger.kernel.org, johannes.schindelin@gmx.de, peff@peff.net, ps@pks.im, me@ttaylorr.com, johncai86@gmail.com, newren@gmail.com, jonathantanmy@google.com Subject: Re: [PATCH v2 0/8] pack-objects: Create an alternative name hash algorithm (recreated) In-Reply-To: (Derrick Stolee's message of "Tue, 3 Dec 2024 23:56:33 -0500") References: Date: Wed, 04 Dec 2024 14:02:14 +0900 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain Derrick Stolee writes: >> These do not sound like versions but more like variants to me, >> especially if one is expected to perform better than another in some >> cases and worse in some other cases. Is it expected that JTan's hash >> to perform better than the original and current hash in almost all >> cases (I would not be surprised at all if that were the case)? > > There are some cases, such as the Linux kernel repo, that have slightly > worse compression using JTan's hash. But the naming conventions in that > repo are such that the v1 name hash was already pretty effective for > that repo. The Git repository has similar issues. See Patch 5 for > detailed analysis of these scenarios using the p5313-pack-objects.sh > test script. So it indeed is more "variant" than "version" where v(N+1) is almost always an implementation of a better idea than vN. > It may be possible to adapt some of the collision rate analysis from > the test helper in Patch 6 to create a tool that recommends or > dynamically selects the hash function that works best for the repo. > Such a feature should be delayed until this code is exercised in more > places. Surely. But that is more advanced feature that can wait. It certainly has to wait until we have a foundation to use more than one variant safely, which this series lays a good foundation for. Thanks.