From owner-freebsd-stable@freebsd.org Mon Mar 18 13:42:23 2019 Return-Path: Delivered-To: freebsd-stable@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id AD0A8153FC6B for ; Mon, 18 Mar 2019 13:42:23 +0000 (UTC) (envelope-from wfc@mintsol.com) Received: from scully.mintsol.com (scully.mintsol.com [199.182.77.206]) by mx1.freebsd.org (Postfix) with ESMTP id 5853E89F09 for ; Mon, 18 Mar 2019 13:42:22 +0000 (UTC) (envelope-from wfc@mintsol.com) Received: from mintsol.com (officecc.mintsol.com [96.85.114.33]) by scully.mintsol.com with esmtp; Mon, 18 Mar 2019 09:37:14 -0400 id 00AC825D.000000005C8F9F0A.00017423 Received: from localhost (localhost [127.0.0.1]) (IDENT: uid 1002) by mintsol.com with esmtp; Mon, 18 Mar 2019 09:37:14 -0400 id 000007DB.5C8F9F0A.0000E7ED Date: Mon, 18 Mar 2019 09:37:14 -0400 (EDT) From: Walter Cramer To: Pete French cc: freebsd-stable@freebsd.org Subject: Re: Observations from a ZFS reorganization on 12-STABLE In-Reply-To: <2baf16fd-3767-1dda-d519-995f7ebaf0cb@ingresso.co.uk> Message-ID: <20190318091431.W52549@mulder.mintsol.com> References: <58eb1994-41bd-cd22-be66-0024bcbc36e6@denninger.net> <2baf16fd-3767-1dda-d519-995f7ebaf0cb@ingresso.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5853E89F09 X-Spamd-Bar: - Authentication-Results: mx1.freebsd.org; spf=pass (mx1.freebsd.org: domain of wfc@mintsol.com designates 199.182.77.206 as permitted sender) smtp.mailfrom=wfc@mintsol.com X-Spamd-Result: default: False [-1.72 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.74)[-0.739,0]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; R_SPF_ALLOW(-0.20)[+a:scully.mintsol.com]; MV_CASE(0.50)[]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[mintsol.com]; NEURAL_HAM_LONG(-0.98)[-0.984,0]; RCVD_COUNT_THREE(0.00)[3]; TO_MATCH_ENVRCPT_SOME(0.00)[]; MX_GOOD(-0.01)[bmx01.pofox.com]; RCPT_COUNT_TWO(0.00)[2]; NEURAL_HAM_SHORT(-0.27)[-0.272,0]; RCVD_NO_TLS_LAST(0.10)[]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:22768, ipnet:199.182.77.0/24, country:US]; IP_SCORE(-0.01)[country: US(-0.07)] X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 18 Mar 2019 13:42:23 -0000 I suggest caution in raising vm.v_free_min, at least on 11.2-RELEASE systems with less RAM. I tried "65536" (256MB) on a 4GB mini-server, with vfs.zfs.arc_max of 2.5GB. Bad things happened when the cron daemon merely tried to run `periodic daily`. A few more details - ARC was mostly full, and "bad things" was 1: `pagedaemon` seemed to be thrashing memory - using 100% of CPU, with little disk activity, and 2: many normal processes seemed unable to run. The latter is probably explained by `man 3 sysctl` (see entry for "VM_V_FREE_MIN"). On Mon, 18 Mar 2019, Pete French wrote: > On 17/03/2019 21:57, Eugene Grosbein wrote: >> I agree. Recently I've found kind-of-workaround for this problem: >> increase vm.v_free_min so when "FREE" memory goes low, >> page daemon wakes earlier and shrinks UMA (and ZFS ARC too) moving some >> memory >> from WIRED to FREE quick enough so it can be re-used before bad things >> happen. >> >> But avoid increasing vm.v_free_min too much (e.g. over 1/4 of total RAM) >> because kernel may start behaving strange. For 16Gb system it should be >> enough >> to raise vm.v_free_min upto 262144 (1GB) or 131072 (512M). >> >> This is not permanent solution in any way but it really helps. > > Ah, thats very interesting, thankyou for that! I;ve been bitten by this issue > too in the past, and it is (as mentioned) much improved on 12, but the act it > could still cause issues worries me. > > -pete. > _______________________________________________ > freebsd-stable@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org"