X-Original-To: pgsql-hackers-postgresql.org@localhost.postgresql.org Received: from localhost (av.hub.org [200.46.204.144]) by postgresql.org (Postfix) with ESMTP id 0B2E19DCA0F; Tue, 21 Mar 2006 16:08:50 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 54998-02; Tue, 21 Mar 2006 16:08:50 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey- X-Greylist: from auto-whitelisted by SQLgrey- Received: from sss.pgh.pa.us (sss.pgh.pa.us [66.207.139.130]) by postgresql.org (Postfix) with ESMTP id C39619DC9E6; Tue, 21 Mar 2006 16:08:45 -0400 (AST) Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1]) by sss.pgh.pa.us (8.13.1/8.13.1) with ESMTP id k2LK8flq019571; Tue, 21 Mar 2006 15:08:41 -0500 (EST) To: Gary Doades cc: pgsql-performance@postgresql.org, pgsql-hackers@postgresql.org Subject: Re: qsort again (was Re: [PERFORM] Strange Create Index behaviour) In-reply-to: <20781.1140046109@sss.pgh.pa.us> References: <43F38867.6010701@gpdnet.co.uk> <19510.1140036968@sss.pgh.pa.us> <19779.1140038874@sss.pgh.pa.us> <43F39E53.1020009@gpdnet.co.uk> <20781.1140046109@sss.pgh.pa.us> Comments: In-reply-to Tom Lane message dated "Wed, 15 Feb 2006 18:28:29 -0500" Date: Tue, 21 Mar 2006 15:08:40 -0500 Message-ID: <19570.1142971720@sss.pgh.pa.us> From: Tom Lane X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, score=0.113 required=5 tests=[AWL=0.113] X-Spam-Score: 0.113 X-Spam-Level: X-Archive-Number: 200603/884 X-Sequence-Number: 81282 Last month I wrote: > It seems clear that our qsort.c is doing a pretty awful job of picking > qsort pivots, while glibc is mostly managing not to make that mistake. I re-ran Gary's test script using the just-committed improvements to qsort.c, and got pretty nice numbers (attached --- compare to http://archives.postgresql.org/pgsql-performance/2006-02/msg00227.php). So it was wrong to blame his problems on the pivot selection --- the culprit was that ill-considered switch to insertion sort. regards, tom lane 100 runtimes for latest port/qsort.c, sorted ascending: Time: 335.481 ms Time: 335.606 ms Time: 335.932 ms Time: 336.039 ms Time: 336.182 ms Time: 336.231 ms Time: 336.711 ms Time: 336.721 ms Time: 336.971 ms Time: 336.982 ms Time: 337.036 ms Time: 337.190 ms Time: 337.223 ms Time: 337.312 ms Time: 337.350 ms Time: 337.423 ms Time: 337.523 ms Time: 337.528 ms Time: 337.565 ms Time: 337.566 ms Time: 337.732 ms Time: 337.741 ms Time: 337.744 ms Time: 337.786 ms Time: 337.790 ms Time: 337.898 ms Time: 337.905 ms Time: 337.952 ms Time: 337.976 ms Time: 338.017 ms Time: 338.123 ms Time: 338.206 ms Time: 338.306 ms Time: 338.514 ms Time: 338.594 ms Time: 338.597 ms Time: 338.683 ms Time: 338.705 ms Time: 338.729 ms Time: 338.748 ms Time: 338.816 ms Time: 338.958 ms Time: 338.963 ms Time: 338.997 ms Time: 339.074 ms Time: 339.106 ms Time: 339.134 ms Time: 339.159 ms Time: 339.226 ms Time: 339.260 ms Time: 339.289 ms Time: 339.341 ms Time: 339.500 ms Time: 339.585 ms Time: 339.595 ms Time: 339.774 ms Time: 339.897 ms Time: 339.927 ms Time: 340.064 ms Time: 340.133 ms Time: 340.172 ms Time: 340.219 ms Time: 340.261 ms Time: 340.323 ms Time: 340.708 ms Time: 340.761 ms Time: 340.785 ms Time: 340.900 ms Time: 340.986 ms Time: 341.339 ms Time: 341.564 ms Time: 341.707 ms Time: 342.155 ms Time: 342.213 ms Time: 342.452 ms Time: 342.515 ms Time: 342.540 ms Time: 342.928 ms Time: 343.548 ms Time: 343.663 ms Time: 344.192 ms Time: 344.952 ms Time: 345.152 ms Time: 345.174 ms Time: 345.444 ms Time: 346.848 ms Time: 348.144 ms Time: 348.842 ms Time: 354.550 ms Time: 356.877 ms Time: 357.475 ms Time: 358.487 ms Time: 364.178 ms Time: 370.730 ms Time: 493.098 ms Time: 648.009 ms Time: 849.345 ms Time: 860.616 ms Time: 936.800 ms Time: 1727.085 ms