From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by dcvr.yhbt.net (Postfix) with ESMTP id C37591F66E for ; Sat, 5 Sep 2020 18:01:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728405AbgIESB2 (ORCPT ); Sat, 5 Sep 2020 14:01:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59206 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728387AbgIESB1 (ORCPT ); Sat, 5 Sep 2020 14:01:27 -0400 Received: from mail-qt1-x843.google.com (mail-qt1-x843.google.com [IPv6:2607:f8b0:4864:20::843]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D8D1C061244 for ; Sat, 5 Sep 2020 11:01:25 -0700 (PDT) Received: by mail-qt1-x843.google.com with SMTP id z2so7169429qtv.12 for ; Sat, 05 Sep 2020 11:01:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ttaylorr-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=WHwd4AMhrIBE6D0lhleBdYTkrQurYuQfkL88OQLvdEo=; b=HBbS3+VXfUFRMLTXXVJnvNA0em6tdS2LH2T2ioptnNUuFE6YA0v7K2KzekB+BqpEw5 XkMJtqzSIUXLMrUgOFcQPekjWOkiYVtc1/Kecb5Fr2Sv1ECvSPQ/P8v9Z3QDob+Zt6Db I+1g0JPsBYuXdIaYGsxyvAoORuB7e1rbhhtPfQwqEI8AmitjzbKQTAilRiXpWQ8Azd7b VZmyz8jqvcnPgDPBAOrYc/thr+k24pCU/u+wab3thXfuJRjBUTI2cqoc4BZqC/fVI7/z uHcY1r+PHAzLCnvz//TG3Rzz+s9mldJWNI9rynOXCcMTZNI4jDLfkb3co8tDFScMiiip INcg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=WHwd4AMhrIBE6D0lhleBdYTkrQurYuQfkL88OQLvdEo=; b=iMLyWHans8MBSpCGX8HKSvnFW8rZ4kcg20IcBO+AOI9MtUmC6oKWNcK6FwxKclJzcz M5TM4WooXtO9UiyUphK/l6OlCwupnJJliVVKOJtbxbr8Oigp0sLvODDA6Ae/GXeZB7uT t23vOFV52mwcLnYLFkFnG1DNOrfFo/UevSZnPz66t5xXOixK8Wg0ehPB81mXQQKYTeb9 Y9FBlV15jEFhybdsNo5abJko9EQYoaYOW9WQeCzMF6oVX21xFcky74Un22+H+riRkfcP m6eOAz3E6mF1HT0kueS0ykWg6hnPqSlE7jcWt+pq4GspKav1RPV8lSPI5/hw70Y1Jw1E IP2Q== X-Gm-Message-State: AOAM533E8Te+ua1unQeukpcWNXQoKy3Jjb6alrwbZPnBQhoR5UzSYWMx 0FUtqFLSo03/QPKYg9OK6L9R+g== X-Google-Smtp-Source: ABdhPJyLqV1J+0SeaL31qjCMWDSSrKEh4ofg28lrIbTUGKtHZOOrX1bFxQWWAtG9Bo61pxH58njUOQ== X-Received: by 2002:ac8:3713:: with SMTP id o19mr12022766qtb.256.1599328884409; Sat, 05 Sep 2020 11:01:24 -0700 (PDT) Received: from localhost ([2605:9480:22e:ff10:f423:2c6a:683a:2c57]) by smtp.gmail.com with ESMTPSA id k6sm7365753qti.23.2020.09.05.11.01.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 05 Sep 2020 11:01:23 -0700 (PDT) Date: Sat, 5 Sep 2020 14:01:20 -0400 From: Taylor Blau To: Jakub =?utf-8?B?TmFyxJlic2tp?= Cc: Taylor Blau , git , Derrick Stolee , Junio Hamano , Jeff King , SZEDER =?utf-8?B?R8OhYm9y?= Subject: Re: [PATCH v4 07/14] bloom: split 'get_bloom_filter()' in two Message-ID: <20200905180120.GB6820@nand.local> References: <85h7sc9m0v.fsf@gmail.com> <20200905173825.GA6820@nand.local> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Sat, Sep 05, 2020 at 07:50:01PM +0200, Jakub Narębski wrote: > Hello, > > On Sat, 5 Sep 2020 at 19:38, Taylor Blau wrote: > > Right, once we get handed back a filter from > > 'get_or_compute_bloom_filter()', we can't distinguish between (a) a > > commit with too many changes to store in a single Bloom filter, and (b) > > a commit with no changes at all. > > We could change how we store either no-changes Bloom filter (as all > zeros minimal size filter), or too-many-changes Bloom filter (as all > ones, i.e. max unsigned value, minimal size filter). This change would > not require to change any user of Bloom filter. I don't think that's true. Say that we changed the empty Bloom filter to be encoded as only having the most-significant bit set. First, we'd have to write a Bloom filter where we didn't have to before. But the real issue is that commit-graph files generated with new clients would suddenly be unreadable by old clients. > > > It's unfortunate that callers can't pick between the two, but this > > implementation is actually an improvement on the status-quo! Why? > > Because right now we'll see an "empty" Bloom filter and recompute it > > because it's "missing", only to discover that it has no changes. > > > > With this patch, we'll say "this filter looks too large", and stop > > computing it, because we have already gone through the effort to compute > > it once (and marked it in the BFXL chunk). > > Can we use this when computing trace2 values? We could, but I don't think it's absolutely necessary. The test coverage in t4216 gives us enough confidence already. > [...] > > > This is a minor issue, though. > > > > Thanks for raising it. I don't think that this is a show-stopper for > > this series. > > I agree. Thanks for your input! > Best, > -- > Jakub Narębski Thanks, Taylor