From owner-freebsd-fs@freebsd.org Mon Apr 2 18:30:36 2018 Return-Path: Delivered-To: freebsd-fs@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 702F4F7D040 for ; Mon, 2 Apr 2018 18:30:36 +0000 (UTC) (envelope-from stilezy@gmail.com) Received: from mail-vk0-x22b.google.com (mail-vk0-x22b.google.com [IPv6:2607:f8b0:400c:c05::22b]) (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 082396B219; Mon, 2 Apr 2018 18:30:36 +0000 (UTC) (envelope-from stilezy@gmail.com) Received: by mail-vk0-x22b.google.com with SMTP id r184so8750753vke.11; Mon, 02 Apr 2018 11:30:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=B3yu1DPdBV/js4zRM3IDntqzxSn8LH54ftNekeA6sdo=; b=h0LG6EiuXBZDELpuPOgtK7ewUD95gHGTCBWCJWtEpljcyNT7U3018EnK1aXNRPP4XT 29qgcxcMhTVJTN3EEzQ6Y3lkZGrVNDFplbsUsxucEUEP5dtIkYlFob6zqUY97uxvs4en Cvhb68yHC8rEvzvJlENtrKi8SiyvAxfMDt6pFb21Hen+m2oQMIpCyATrseBAf9KNspNP ILw1LB6RJ5xyM9u3IIA13JzV/26GXuUzEhMfi64CfP2dGSnzcZtX/Co0Z9YNA2EuFp6V z/kqRjKPN8LOLZV9dKviYeCTTzLWgOHOumfq44NIaQ5nSUS9l8t/6FSk0j4C5g7zueRc Ylig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=B3yu1DPdBV/js4zRM3IDntqzxSn8LH54ftNekeA6sdo=; b=ourwkwibUNh/5fUru+iD0LO5WjGO1V60946k5wO9Vp5tJFP9OQiHkTlFwYBtNyghrY 8VjbVcSaGOZ5Q30aaItXniMFmrYVe5WuuTcnevyxQsz3aK2YenMgDi4f8wA2BARmHaKo GeaSfZSctnJQx8gZivpVU/dquU7S07VC0Fv7yBN9BJrwe+1ZJsH9N1CWFY2pwGyPWQUr j8l4bbvy+Dc64unYePcHgOE7ggQW3rzZ6gyNMfI9bUa8K7B3Qw3uK8H0k8CJxm91WWVu R/urLWFdrArl/28My+KYAPWvRta5TkdMZjJg14uYLcuXRmX//l6TgX+b9oBsEgwH0gbv L3Hg== X-Gm-Message-State: ALQs6tDfYkeLjGsp9tiyGqaat6taSunNtWzN9mzJNPftRTOJno72U41g LUBM8eW5G875PGhxOqcnTEV1m9BJlLF1xvV99qyFNQ== X-Google-Smtp-Source: AIpwx4/wTvtORWzmy/ZLHrxE9yKUVMCu+mQeVrKIXDqsKzAvRORpzEK5PW+wzYP1b6O1HKqTYtbfniONsB0fUjEfBy0= X-Received: by 10.31.41.130 with SMTP id p124mr5401775vkp.8.1522693835481; Mon, 02 Apr 2018 11:30:35 -0700 (PDT) MIME-Version: 1.0 Received: by 10.103.219.148 with HTTP; Mon, 2 Apr 2018 11:30:05 -0700 (PDT) In-Reply-To: <14c857cc-463f-a56e-bcf6-c0702da6d3bc@FreeBSD.org> References: <14c857cc-463f-a56e-bcf6-c0702da6d3bc@FreeBSD.org> From: Stilez Stilezy Date: Mon, 2 Apr 2018 19:30:05 +0100 Message-ID: Subject: Re: ZFS dedup write pathway - possible inefficiency or..? To: Andriy Gapon Cc: freebsd-fs@freebsd.org Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.25 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 Apr 2018 18:30:36 -0000 Thanks on that tip, Andriy, I don't have the knowledge to tell if that's the first of the 2 issues I'm seeing. It could be. What exactly is that bug describing and what behaviour would it create? Assuming it's the same - 1) Are there any known workarounds or sysctls that help to reduce the issue? 2) Are there any easy diagnostic tests I can easily do, to confirm if this is the same behaviour as that bug? Nobody else uses the test system, so I can change any sysctls to sane or extreme values for testing, or create large txg's and spread out reads and writes to see what's happening and what coincides with what. Thanks again On 2 April 2018 at 18:47, Andriy Gapon wrote: > On 02/04/2018 16:36, Stilez Stilezy wrote: > > The first issue is specific to the > > dedup write pathway. I've tested locally to a point where it seems it's > > not due to inadequate hardware and it's very consistent and specific, > even > > on idle conditions/minimal load. I'm wondering whether there's a code > > bottleneck specifically affecting just the dedup write pathway. > > I think that this might be https://www.illumos.org/issues/8353 > > -- > Andriy Gapon >