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-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.9 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_NONE shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 3717E1F4BD for ; Wed, 2 Oct 2019 15:57:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728930AbfJBP5X (ORCPT ); Wed, 2 Oct 2019 11:57:23 -0400 Received: from cloud.peff.net ([104.130.231.41]:38084 "HELO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1727103AbfJBP5X (ORCPT ); Wed, 2 Oct 2019 11:57:23 -0400 Received: (qmail 25097 invoked by uid 109); 2 Oct 2019 15:57:23 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with SMTP; Wed, 02 Oct 2019 15:57:23 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 22997 invoked by uid 111); 2 Oct 2019 16:00:00 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) by peff.net (qpsmtpd/0.94) with (TLS_AES_256_GCM_SHA384 encrypted) ESMTPS; Wed, 02 Oct 2019 12:00:00 -0400 Authentication-Results: peff.net; auth=none Date: Wed, 2 Oct 2019 11:57:22 -0400 From: Jeff King To: Junio C Hamano Cc: Christian Couder , git@vger.kernel.org, Christian Couder , Ramsay Jones Subject: Re: [RFC PATCH 10/10] pack-objects: improve partial packfile reuse Message-ID: <20191002155721.GD6116@sigill.intra.peff.net> References: <20190913130226.7449-1-chriscool@tuxfamily.org> <20190913130226.7449-11-chriscool@tuxfamily.org> <20190914020225.GB28422@sigill.intra.peff.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Fri, Sep 13, 2019 at 08:06:01PM -0700, Junio C Hamano wrote: > Jeff King writes: > > > On Fri, Sep 13, 2019 at 03:29:00PM -0700, Junio C Hamano wrote: > > > >> This comment has nothing to do with the change, but the way the > >> patch is presented is quite hard to follow, in that the preimage or > >> the common context lines do not help understand what the new code is > >> doing at all ;-) > >> > >> I'll come back to the remainder of the patch later. Thanks. > > > > I applaud Christian's effort to tease it out into separate patches. > > Ah, no question about it. I have a suspicion that 10/10 alone may > still be a bit too large a ball of wax, but with all the earlier > preparatory steps are bite-sized and trivial to see how they are > correct. > > The "way the patch is presented" comment was not at all about what > Christian did, but was about what the diff machinery computed when > comparing the 9th step Christian created and the final step. In its > attempt to find and align common context lines, it ended up finding > blank lines and almost nothing else in the earlier part of the > patch, not just making it harder to read the new helper function > (i.e. the best way to read record_reused_object(), for example, is > to look only at '+' and ' ' lines, because the '-' lines are > irrelevant), it also made it hard to see what got discarded. Hmm, I see the early parts of this graduated to 'next'. I'm not sure everything there is completely correct, though. E.g. I'm not sure of the reasoning in df75281e78 (ewah/bitmap: always allocate 2 more words, 2019-09-13). I think the "block+1" there is actually because "block" might be "0". Prior to 2820ed171a (ewah/bitmap: introduce bitmap_word_alloc(), 2019-09-13) from the same series, that could never be the case because we know that we always start with at least 32 allocated words. But after that we _could_ start with an empty word array, and allocating "block * 2" would not make forward progress. And then the "2 more words" thing is used as justification in the next patch, 04a32d357f (pack-bitmap: don't rely on bitmap_git->reuse_objects, 2019-09-13). I won't say that there isn't some subtle dependency there, but I certainly don't remember any logic like that at all. ;) So I think it might bear a little more scrutiny. I'm sorry for being so slow on giving it a more careful review. I was traveling for work, then playing catch-up, and am now going on vacation. So it might be a little while yet. -Peff