From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.176.0/21 X-Spam-Status: No, score=-3.3 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MSGID_FROM_MTA_HEADER,RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 From: Linus Torvalds Subject: Re: [RFC \ WISH] Add -o option to git-rev-list Date: Sun, 10 Dec 2006 14:16:30 -0800 (PST) Message-ID: References: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII NNTP-Posting-Date: Sun, 10 Dec 2006 22:16:56 +0000 (UTC) Cc: Git Mailing List , Junio C Hamano , Alex Riesen , Shawn Pearce Return-path: Envelope-to: gcvg-git@gmane.org In-Reply-To: X-MIMEDefang-Filter: osdl$Revision: 1.162 $ X-Scanned-By: MIMEDefang 2.36 Precedence: bulk X-Mailing-List: git@vger.kernel.org Archived-At: Received: from vger.kernel.org ([209.132.176.167]) by dough.gmane.org with esmtp (Exim 4.50) id 1GtWyR-0000bh-2Y for gcvg-git@gmane.org; Sun, 10 Dec 2006 23:16:43 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758797AbWLJWQk (ORCPT ); Sun, 10 Dec 2006 17:16:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759006AbWLJWQk (ORCPT ); Sun, 10 Dec 2006 17:16:40 -0500 Received: from smtp.osdl.org ([65.172.181.25]:41036 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758797AbWLJWQj (ORCPT ); Sun, 10 Dec 2006 17:16:39 -0500 Received: from shell0.pdx.osdl.net (fw.osdl.org [65.172.181.6]) by smtp.osdl.org (8.12.8/8.12.8) with ESMTP id kBAMGVID025564 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO); Sun, 10 Dec 2006 14:16:32 -0800 Received: from localhost (shell0.pdx.osdl.net [10.9.0.31]) by shell0.pdx.osdl.net (8.13.1/8.11.6) with ESMTP id kBAMGUUQ004863; Sun, 10 Dec 2006 14:16:31 -0800 To: Marco Costalba Sender: git-owner@vger.kernel.org On Sun, 10 Dec 2006, Marco Costalba wrote: > > Ok. Perhaps I'm doing something wrong but the following code it's > always 10% slower then the temporary file one (4.7s against 4.3s for > linux tree) Why do you seem to be doing a "new" on every iteration inside the loop? Also, why do you have that strange FILE_BLOCK_SIZE thing, and in particular the "if (len < FILE_BLOCK_SIZE)" check? One thing that pipes vs files do is the blocking factor. Especially with older kernels, I _guarantee_ you that you'll only ever get 4kB at a time, so because of that "if (len < 64kB) break" thing, the only thing you're doing is to make sure things suck performance-wise, and you won't be reading the rest of the data until 100ms later. IOW, your code is written for a file, and makes no sense there either (checking "feof(file)" is wrong, since you may well have hit the EOF *at*that*time*, but the file may GROW since you are doing it all in the background, so you can't rely on feof() anyway). For a pipe, what you should do is to make sure it's in nonblocking mode, and just continue reading until it gets no more. And instead of using a timeout, you should use poll() or something to get notified when there is more data. IOW, the reason it's slow is because you're doing the wrong thing.