From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0661C33C9E for ; Fri, 17 Jan 2020 18:11:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B61D920748 for ; Fri, 17 Jan 2020 18:11:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="EsaOs8ZT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729011AbgAQSLP (ORCPT ); Fri, 17 Jan 2020 13:11:15 -0500 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:34706 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726603AbgAQSLO (ORCPT ); Fri, 17 Jan 2020 13:11:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579284673; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hUtVwDqnuDn/t5tUW8sUkWv84d3FlHqi58OEIXe+Yqw=; b=EsaOs8ZTSbFnW0FppqzlaWoCZwp3rGho+yaNbjzkKgYSP7zX5DxFKbsX/rpfVMnQ7q4VX/ lHyApkhppZwPmenzf3/9nZBjbUrcpkoIlae9UlN6Lxv6wRdhlwPOCzMT2BJ2E0hfFnZ2Ox HprftXMDokyXMK0B4AbfGvWeItW+03M= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-115-zYkDQlh8NU-813ws2COrgA-1; Fri, 17 Jan 2020 13:11:09 -0500 X-MC-Unique: zYkDQlh8NU-813ws2COrgA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7D871100551C; Fri, 17 Jan 2020 18:11:08 +0000 (UTC) Received: from llong.remote.csb (dhcp-17-59.bos.redhat.com [10.18.17.59]) by smtp.corp.redhat.com (Postfix) with ESMTP id B55DD5D9CD; Fri, 17 Jan 2020 18:11:07 +0000 (UTC) Subject: Re: Performance regression introduced by commit b667b8673443 ("pipe: Advance tail pointer inside of wait spinlock in pipe_read()") From: Waiman Long To: Linus Torvalds Cc: David Howells , Alexander Viro , "linux-fsdevel@vger.kernel.org" , Linux List Kernel Mailing References: <5c184396-7cc8-ee72-2335-dce9a977c8d4@redhat.com> Organization: Red Hat Message-ID: Date: Fri, 17 Jan 2020 13:11:07 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <5c184396-7cc8-ee72-2335-dce9a977c8d4@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Content-Transfer-Encoding: quoted-printable Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 1/17/20 12:29 PM, Waiman Long wrote: > On 1/17/20 12:05 PM, Linus Torvalds wrote: >> [ on mobile, sorry for html crud ] >> >> On Fri, Jan 17, 2020, 08:53 Waiman Long > > wrote: >> >> >> I had found that parallel kernel build became much slower when a >> 5.5-based kernel is used. On a 2-socket 96-thread x86-64 system, t= he >> "make -j88" time increased from less than 3 minutes with the 5.4 >> kernel >> to more than double with the 5.5 kernel. >> >> >> I suspect you may have hit the same bug in the GNU make jobserver >> that I did. >> >> It's timing-sensitive, and under the right circumstances the make >> jobserver loses job tickets to other jobservers that have a child >> that died, but they are blocked waiting for a new ticket, so they >> aren't releasing (or re-using) the one that the child death would >> free up. >> >> End result: a big lack of parallelism, and a much slower build. >> >> GNU make v4.2.1 is buggy. The fix was done over two years ago, but >> there hasn't been a new release since then, so a lot of distributions >> have the buggy version.. >> >> The fix is commit=C2=A0b552b05 ("[SV 51159] Use a non-blocking read wi= th >> pselect to avoid hangs.") In the make the git tree. >> >> >> =C2=A0 =C2=A0 =C2=A0Linus > > Thanks for the information. > > Yes, I did use make v4.2.1 which is the version that is shipped in > RHEL8. I will build new make and try it. > > Thanks, > Longman > I built a make with the lastest make git tree and the problem was gone with the new make. So it was a bug in make not the kernel. Sorry for the noise. Cheers, Longman