From owner-freebsd-current@freebsd.org Mon Aug 1 16:38:10 2016 Return-Path: Delivered-To: freebsd-current@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E5253BAA925 for ; Mon, 1 Aug 2016 16:38:10 +0000 (UTC) (envelope-from sobomax@sippysoft.com) Received: from mail-it0-x231.google.com (mail-it0-x231.google.com [IPv6:2607:f8b0:4001:c0b::231]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id B36E51833 for ; Mon, 1 Aug 2016 16:38:10 +0000 (UTC) (envelope-from sobomax@sippysoft.com) Received: by mail-it0-x231.google.com with SMTP id f6so175888835ith.0 for ; Mon, 01 Aug 2016 09:38:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sippysoft-com.20150623.gappssmtp.com; s=20150623; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to; bh=4bTPUAdYH1+Lg5yKhdzaTOyT/HDfGgJNE4kpc5K3aYU=; b=DASR2FxzxJ4EMYHndDL+ijLuUiBToFELrYE1mt6M4F1KKgir9o1vOGsP3nNrTcewLV 7DaEdrFmpVm9+GJwcPDV701rFgMXx/XBhBeSEeQu1fYq3vfzAGrmVNdCX49pgNyCjQ/+ FnWNGLnlWfSNQnwIL049j/JUEPT/pD87UlrC1eji9lpwTEj/x1bvJ63KgeAmQQ7pM4/G 1rqO+Vo7KDczePMwWghDYjKMynWNB3/cpSIXCzNIvuEg/AKB43Y3HutGFBfPs2cEhXEQ tC974oFhdKVR9p0hTMsJlzc2V5ebYaUfjlakyZtgSGXHKUuQUp+tVtiD9d49buf6XORt W+6A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to; bh=4bTPUAdYH1+Lg5yKhdzaTOyT/HDfGgJNE4kpc5K3aYU=; b=gogrPRXv4jlyoj6uqE7aYTHZHh+uTJRz+VQuzbx0Ee2Qn6L118sJNQHuiMfuy6CmRR zEfYXzyC4IYFeM6MmIIakmR6nkHWII052wUBk2zGDd7vO8yBfTG43HpMHCVz2jiT9T8+ l1lt3joVmawL5EOHWw3eDsFM7N/Y1Tpq+FNH1ogJgGrH5KrZjBKDLueZ3YIeZ5er/DLI b91HG921bek/LUFahMMu6TpmbVCCuiEVKFVSkADxrscRlgQJeX3hMfabeVS7oYaE8vYm GuOalmxrJK8UIr9aKeR5TmUT/eFaulh57NcJ/D3g+H8mwTyiMGOOrTPpc2TaHO/oSYU6 lh3A== X-Gm-Message-State: AEkoouuV+Bixh7he1SRH2ynpEGjC5GquaA+puUmMBaDkbdoN0DRQ4j2kdF8DuAmQjxsm9q9XnqmkdHmibkpDamAk X-Received: by 10.36.90.79 with SMTP id v76mr55442487ita.16.1470069489795; Mon, 01 Aug 2016 09:38:09 -0700 (PDT) MIME-Version: 1.0 Sender: sobomax@sippysoft.com Received: by 10.36.13.139 with HTTP; Mon, 1 Aug 2016 09:38:09 -0700 (PDT) In-Reply-To: <20160731203612.GH9408@dft-labs.eu> References: <20160731095706.GB9408@dft-labs.eu> <20160731203612.GH9408@dft-labs.eu> From: Maxim Sobolev Date: Mon, 1 Aug 2016 09:38:09 -0700 X-Google-Sender-Auth: UwqdkXZc2FzQ-zB1HPTwiY-6bjg Message-ID: Subject: Re: [PATCH] randomized delay in locking primitives, take 2 To: Mateusz Guzik , Adrian Chadd , John Baldwin , freebsd-current , Konstantin Belousov Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.22 X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 01 Aug 2016 16:38:11 -0000 On Sun, Jul 31, 2016 at 1:36 PM, Mateusz Guzik wrote: > On Sun, Jul 31, 2016 at 07:03:08AM -0700, Adrian Chadd wrote: > > Hi, > > > > Did you test on any 1, 2, 4, 8 cpu machines? just to see if there are > > any performance degredations on lower count CPUs? > > > > I did not test on machines which physically that few cpus, but I did > test the impact on microbenchmark with 2 and 4 threads on the 80-way > machine. There was no difference. > Well, arguably running 4 threads on a 80-way machine is not quite the same as running the same 4 threads on 4-way or 8-way machine. Unless you actually bind your test threads to a specific CPUs, on a bigger system scheduler is free to migrate your thread on another CPU if all 4 are spinning, this might not the option for smaller box. I suggest you at very least re-run your benchmark on a virtual machine with small CPUs count assigned, it should be quite easy to do so on your monster box. -Maxim