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=-3.1 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: kernel.org mirroring (Re: [GIT PULL] MMC update) Date: Thu, 7 Dec 2006 11:30:29 -0800 (PST) Message-ID: References: <45708A56.3040508@drzeus.cx> <457151A0.8090203@drzeus.cx> <45744FA3.7020908@zytor.com> <45778AA3.7080709@zytor.com> <4577A84C.3010601@zytor.com> <45785697.1060001@zytor.com> <457868AA.2030605@zytor.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII NNTP-Posting-Date: Thu, 7 Dec 2006 19:31:47 +0000 (UTC) Cc: Kernel Org Admin , Git Mailing List , Jakub Narebski Return-path: Envelope-to: gcvg-git@gmane.org In-Reply-To: <457868AA.2030605@zytor.com> 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 1GsOy7-0006m2-A5 for gcvg-git@gmane.org; Thu, 07 Dec 2006 20:31:43 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937999AbWLGTbk (ORCPT ); Thu, 7 Dec 2006 14:31:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S938000AbWLGTbk (ORCPT ); Thu, 7 Dec 2006 14:31:40 -0500 Received: from smtp.osdl.org ([65.172.181.25]:59088 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937999AbWLGTbj (ORCPT ); Thu, 7 Dec 2006 14:31:39 -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 kB7JUUID011754 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO); Thu, 7 Dec 2006 11:30:40 -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 kB7JUT0h022691; Thu, 7 Dec 2006 11:30:30 -0800 To: "H. Peter Anvin" Sender: git-owner@vger.kernel.org On Thu, 7 Dec 2006, H. Peter Anvin wrote: > > What it could do better is it could prevent multiple identical queries from > being launched in parallel. That's the real problem we see; under high load, > Apache times out so the git query never gets into the cache; but in the > meantime, the common queries might easily have been launched 20 times in > parallel. Unfortunately, the most common queries are also extremely > expensive. Ahh. I'd have expected that apache itself had some serialization facility, that would kind of go hand-in-hand with any caching. It really would make more sense to have anything that does caching serialize the address that gets cached (think "page cache" layer in the kernel: the _cache_ is also the serialization point, and is what guarantees that we don't do stupid multiple reads to the same address). I'm surprised that Apache can't do that. Or maybe it can, and it just needs some configuration entry? I don't know apache.. I realize that because Apache doesn't know before-hand whether something is cacheable or not, it must probably _default_ to running the CGI scripts to the same address in parallel, but it would be stupid to not have the option to serialize. That said, from some of the other horrors I've heard about, "stupid" may be just scratching at the surface.