From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff King Subject: Re: [PATCH 4/4] gc --aggressive: three phase repacking Date: Tue, 18 Mar 2014 01:07:27 -0400 Message-ID: <20140318050727.GA14769@sigill.intra.peff.net> References: <1394976904-15395-1-git-send-email-pclouds@gmail.com> <1394976904-15395-6-git-send-email-pclouds@gmail.com> <20140318045050.GB8240@sigill.intra.peff.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: git@vger.kernel.org To: =?utf-8?B?Tmd1eeG7hW4gVGjDoWkgTmfhu41j?= Duy X-From: git-owner@vger.kernel.org Tue Mar 18 06:07:34 2014 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 1WPmFS-0001Ty-5M for gcvg-git-2@plane.gmane.org; Tue, 18 Mar 2014 06:07:34 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752099AbaCRFHa convert rfc822-to-quoted-printable (ORCPT ); Tue, 18 Mar 2014 01:07:30 -0400 Received: from cloud.peff.net ([50.56.180.127]:41638 "HELO peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751083AbaCRFH3 (ORCPT ); Tue, 18 Mar 2014 01:07:29 -0400 Received: (qmail 22078 invoked by uid 102); 18 Mar 2014 05:07:29 -0000 Received: from c-71-63-4-13.hsd1.va.comcast.net (HELO sigill.intra.peff.net) (71.63.4.13) (smtp-auth username relayok, mechanism cram-md5) by peff.net (qpsmtpd/0.84) with ESMTPA; Tue, 18 Mar 2014 00:07:29 -0500 Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Tue, 18 Mar 2014 01:07:27 -0400 Content-Disposition: inline In-Reply-To: <20140318045050.GB8240@sigill.intra.peff.net> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On Tue, Mar 18, 2014 at 12:50:50AM -0400, Jeff King wrote: > On Sun, Mar 16, 2014 at 08:35:04PM +0700, Nguy=E1=BB=85n Th=C3=A1i Ng= =E1=BB=8Dc Duy wrote: >=20 > > As explained in the previous commit, current aggressive settings > > --depth=3D250 --window=3D250 could slow down repository access > > significantly. Notice that people usually work on recent history on= ly, > > we could keep recent history more loosely packed, so that repo acce= ss > > is fast most of the time while the pack file remains small. >=20 > One thing I have not seen is real-world timings showing the slowdown > based on --depth. Did I miss them, or are we just making assumptions > based on one old case from 2009 (that, AFAIK does not have real numbe= rs, > just speculation)? Has anyone measured the effect of bumping the delt= a > cache size (and its hash implementation)? Just as a very quick, rough data point, here are before-and-after timings for the patch below doing "git rev-list --objects --all" on my linux.git, which is a mix of "--aggressive" and normal packing (I didn'= t do a "repack -f", but it's partially what I've downloaded from k.org an= d what I've repacked in various experiments over the past few months). [before] real 0m28.824s user 0m28.620s sys 0m0.232s [after] real 0m21.694s user 0m21.544s sys 0m0.172s The numbers below are completely pulled out of a hat, so we can perhaps do even better. But I think it shows that there is room for improvement in the delta base cache. --- diff --git a/environment.c b/environment.c index c3c8606..73ed670 100644 --- a/environment.c +++ b/environment.c @@ -37,7 +37,7 @@ int core_compression_seen; int fsync_object_files; size_t packed_git_window_size =3D DEFAULT_PACKED_GIT_WINDOW_SIZE; size_t packed_git_limit =3D DEFAULT_PACKED_GIT_LIMIT; -size_t delta_base_cache_limit =3D 16 * 1024 * 1024; +size_t delta_base_cache_limit =3D 128 * 1024 * 1024; unsigned long big_file_threshold =3D 512 * 1024 * 1024; const char *pager_program; int pager_use_color =3D 1; diff --git a/sha1_file.c b/sha1_file.c index b37c6f6..a9ab8e3 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -1944,7 +1944,7 @@ static void *unpack_compressed_entry(struct packe= d_git *p, return buffer; } =20 -#define MAX_DELTA_CACHE (256) +#define MAX_DELTA_CACHE (1024) =20 static size_t delta_base_cached; =20