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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F6F9C433EF for ; Mon, 27 Sep 2021 15:39:33 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8570360EBB for ; Mon, 27 Sep 2021 15:39:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 8570360EBB Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632757171; h=from:from:sender:sender:reply-to: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:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=x5JqPXlo25DEcrxLW8/811D56z0CLZACS6A8oes8okM=; b=OhaoT7nLdzlh3D51jfoXffbXXA72sUpYrh3FmSHGilh45kbtRf3X5IkyuZZ7hXn6mTZ+jt ftUesg9a6OT5ln4II2BgcMsfSYSocBsChgbheAVdyqG8yFBmiHKbq83TokNrUnNSbalrNu 1E2gYyT0SvE+L+Xlgup4gFxclIV85CM= 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-331-zLGmnmQsOzOBnuS64jpWHQ-1; Mon, 27 Sep 2021 11:39:30 -0400 X-MC-Unique: zLGmnmQsOzOBnuS64jpWHQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0E3D4100C62E; Mon, 27 Sep 2021 15:39:05 +0000 (UTC) Received: from colo-mx.corp.redhat.com (colo-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.21]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 03E095D740; Mon, 27 Sep 2021 15:39:01 +0000 (UTC) Received: from lists01.pubmisc.prod.ext.phx2.redhat.com (lists01.pubmisc.prod.ext.phx2.redhat.com [10.5.19.33]) by colo-mx.corp.redhat.com (Postfix) with ESMTP id A06994EA2A; Mon, 27 Sep 2021 15:38:33 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by lists01.pubmisc.prod.ext.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id 18RFcU81026248 for ; Mon, 27 Sep 2021 11:38:30 -0400 Received: by smtp.corp.redhat.com (Postfix) id 7FC61100164A; Mon, 27 Sep 2021 15:38:30 +0000 (UTC) Received: from redhat.com (unknown [10.15.80.136]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 043AD100238C; Mon, 27 Sep 2021 15:38:29 +0000 (UTC) Date: Mon, 27 Sep 2021 10:38:22 -0500 From: David Teigland To: Peter Rajnoha Message-ID: <20210927153822.GA4779@redhat.com> References: <20210607214835.GB8181@redhat.com> <20210608122901.o7nw3v56kt756acu@alatyr-rpi.brq.redhat.com> <20210909194417.GC19437@redhat.com> <20210927100032.xczilyd5263b4ohk@alatyr-rpi.brq.redhat.com> MIME-Version: 1.0 In-Reply-To: <20210927100032.xczilyd5263b4ohk@alatyr-rpi.brq.redhat.com> User-Agent: Mutt/1.8.3 (2017-05-23) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-loop: linux-lvm@redhat.com Cc: zkabelac@redhat.com, bmarzins@redhat.com, martin.wilck@suse.com, heming.zhao@suse.com, linux-lvm@redhat.com Subject: Re: [linux-lvm] Discussion: performance issue on event activation mode X-BeenThere: linux-lvm@redhat.com X-Mailman-Version: 2.1.12 Precedence: junk Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-lvm-bounces@redhat.com Errors-To: linux-lvm-bounces@redhat.com X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=linux-lvm-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On Mon, Sep 27, 2021 at 12:00:32PM +0200, Peter Rajnoha wrote: > > - We could use the new lvm-activate-* services to replace the activation > > generator when lvm.conf event_activation=0. This would be done by simply > > not creating the event-activation-on file when event_activation=0. > > ...the issue I see here is around the systemd-udev-settle: Thanks, I have a couple questions about the udev-settle to understand that better, although it seems we may not need it. > - the setup where lvm-activate-vgs*.service are always there (not > generated only on event_activation=0 as it was before with the > original lvm2-activation-*.service) practically means we always > make a dependency on systemd-udev-settle.service, which we shouldn't > do in case we have event_activation=1. Why wouldn't the event_activation=1 case want a dependency on udev-settle? > - If we want to make sure that we run our "non-event-based activation" > after systemd-udev-settle.service, we also need to use > "After=systemd-udev-settle.service" (the "Wants" will only make the > udev settle service executed, but it doesn't order it with respect > to our activation services, so it can happen in parallel - we want > it to happen after the udev settle). So we may not fully benefit from settling unless we use After (although the benefits are uncertain as mentioned below.) > Now the question is whether we really need the systemd-udev-settle at > all, even for that non-event-based lvm activation. The udev-settle is > just to make sure that all the udev processing and udev db content is > complete for all triggered devices. But if we're not reading udev db and > we're OK that those devices might be open in parallel to lvm activation > period (e.g. because there's blkid scan done on disks/PVs), we should be > OK even without that settle. However, we're reading some info from udev db, > right? (like the multipath component state etc.) - Reading the udev db: with the default external_device_info_source=none we no longer ask the udev db for any info about devs. (We now follow that setting strictly, and only ask udev when source=udev.) - Concurrent blkid and activation: I can't find an issue with this (couldn't force any interference with some quick tests.) - I wonder if After=udev-settle could have an incidental but meaningful effect of more PVs being in place before the service runs? I'll try dropping udev-settle in all cases to see how things look. Dave _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://listman.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/