From mboxrd@z Thu Jan 1 00:00:00 1970 From: Junio C Hamano Subject: Re: Lockless Refs? Date: Fri, 04 Jan 2013 13:28:32 -0800 Message-ID: <7vip7ctz7j.fsf@alter.siamese.dyndns.org> References: <20121221080449.GA21741@sigill.intra.peff.net> <201212271611.52203.mfick@codeaurora.org> <201212310330.53835.mfick@codeaurora.org> <201301031652.44982.mfick@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Michael Haggerty , Shawn Pearce , Jeff King , git@vger.kernel.org To: Martin Fick X-From: git-owner@vger.kernel.org Fri Jan 04 22:28:58 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 1TrEox-0000tb-CI for gcvg-git-2@plane.gmane.org; Fri, 04 Jan 2013 22:28:55 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755240Ab3ADV2g (ORCPT ); Fri, 4 Jan 2013 16:28:36 -0500 Received: from b-pb-sasl-quonix.pobox.com ([208.72.237.35]:44710 "EHLO smtp.pobox.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754934Ab3ADV2e (ORCPT ); Fri, 4 Jan 2013 16:28:34 -0500 Received: from smtp.pobox.com (unknown [127.0.0.1]) by b-sasl-quonix.pobox.com (Postfix) with ESMTP id 1F45AB5CB; Fri, 4 Jan 2013 16:28:34 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; s=sasl; bh=1fzrM4QqBYMkQ1hkaozqEWNt4b4=; b=DQarHr KXOqLx0HN9HNb0xIiYCt1TPcLvPTKFC6K93LMMuMn4xNFs99yfjhgbcrwILmt+TB HzVekBJVjRPy8GNoDN7HcFu4DBWKakduucZhvYiYy2XPw13ZsSZ19dxEeZ25Xb+m Yx/AuKbM/Tk1Gu+dt9Y84L7yatuLpTNiGVaEk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; q=dns; s=sasl; b=vy99LeVSnaGXt7lwerdqnUxNZZF1hYL8 sPj7uEor/w9Zz+JIDDl9In0+0PAVEpnrWMmltaQsr7ALXAhPourhAqSwmFr4VjHp ykcpeytl7otp/KGU6NV9fMqR1R7YKlSWE5UVu0Vo5CWhKUyc4SIz+LuIebkjF1Ro KR5T5MfVLsg= Received: from b-pb-sasl-quonix.pobox.com (unknown [127.0.0.1]) by b-sasl-quonix.pobox.com (Postfix) with ESMTP id 0F6F1B5CA; Fri, 4 Jan 2013 16:28:34 -0500 (EST) Received: from pobox.com (unknown [98.234.214.94]) (using TLSv1 with cipher DHE-RSA-AES128-SHA (128/128 bits)) (No client certificate requested) by b-sasl-quonix.pobox.com (Postfix) with ESMTPSA id 7EC3CB5C9; Fri, 4 Jan 2013 16:28:33 -0500 (EST) In-Reply-To: <201301031652.44982.mfick@codeaurora.org> (Martin Fick's message of "Thu, 3 Jan 2013 16:52:44 -0700") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) X-Pobox-Relay-ID: B1201B96-56B5-11E2-B28F-F0CE2E706CDE-77302942!b-pb-sasl-quonix.pobox.com Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: Martin Fick writes: > Any thoughts on this idea? Is it flawed? I am trying to > write it up in a more formal generalized manner and was > hoping to get at least one "it seems sane" before I do. The general impression I have been getting was that this isn't even worth the effort and the resulting complexity of the code, given Peff's observations earlier in the thread that ref update conflicts and leftover locks are reasonably rare in practice. But perhaps I has been mis-reading the discussion. I also have this suspicion that if you really want to shoot for multi-repository transactions in an massively scaled repository hosting environment, you would rather want to not rely on hacks based on filesystem semantics, but instead want to RPC with a dedicated "ref management service" that knows the transaction semantics you want, but that could become a much larger change. I dunno.