From owner-freebsd-fs@freebsd.org Wed Apr 6 20:43:15 2016 Return-Path: Delivered-To: freebsd-fs@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 65549B06562 for ; Wed, 6 Apr 2016 20:43:15 +0000 (UTC) (envelope-from leo.prasath@gmail.com) Received: from mail-io0-x22a.google.com (mail-io0-x22a.google.com [IPv6:2607:f8b0:4001:c06::22a]) (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 32404122B for ; Wed, 6 Apr 2016 20:43:15 +0000 (UTC) (envelope-from leo.prasath@gmail.com) Received: by mail-io0-x22a.google.com with SMTP id 2so70793907ioy.1 for ; Wed, 06 Apr 2016 13:43:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:from:date:message-id:subject:to; bh=Bkd8PagxCyUYYTVZg0WErnat9bIq09FHLPmZgbZV5cw=; b=gnr6s6kO3ScHcX5lbDZ0gzK5Pwbd4IcVH1Eo6tb0Lik2mBoDfwNJhQVbZu2CC1tyFJ OYW0fpF7vSotFcxyKsT+v8rg+Fd859H2Vc3NJp50akHmd7AYB4g9bfvVv+Ckvbx4HNIW I+/uA2mjuZsjpV77dk4PRDTJowxTddLQsYsBl95H5++ppm4MMJEF1m10UzgH824KFx8L Fvh4sMpxLuVmCjU0fEL26IHWyt3BL9ydzXwxeRJEP4sjyFWYhbIv8G2YP8Zt1knl+jVc 24ThnCCt2qWAH4NmQaCuf56YRcB6ujmShNcFZH4FwyI6wfMfM2jYoVFmXtmL2MV9uoqg UTjg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=Bkd8PagxCyUYYTVZg0WErnat9bIq09FHLPmZgbZV5cw=; b=ih4fXAPHMMwT/T5s8gssoIiNDxz03m4lENK2aOt4syKPnB998hK5HU67NKs3aSE+4H iHrP+gl8Il22FB8VD8Ax5K1xOXbWTpP8VdAZstX7NhJre1ROeA7DRul67zjb3Y6UbOk6 9mjENez57JEZxCW4fqtxAcqd5pCSIQjgHxyd1mfmccHVhMUdAKcT89TyZnjGweg2RYxQ ftr9VQeCo6AqpUNL1hFpH/rZUHfCcle+XpBQSyfKJ2rRIDCpHmCojjQ+vMKdksW/sy7c VVTdNwoKzDnuQ6qd8Pj4gHUl7QYt91l4l4xbrstwHo63ebCy5jUAnGM5QzBCecHCDPLI fFTQ== X-Gm-Message-State: AD7BkJLrSJ/9VEtTcoyAr7ONjtFOhPfinDfTW86FqEQmO50/zcnKKCcH9EyXeySN3sPa5YAxtICDAAarWDAMVA== X-Received: by 10.107.29.212 with SMTP id d203mr22773155iod.6.1459975394575; Wed, 06 Apr 2016 13:43:14 -0700 (PDT) MIME-Version: 1.0 Received: by 10.36.91.83 with HTTP; Wed, 6 Apr 2016 13:42:55 -0700 (PDT) From: Leo Prasath Arulraj Date: Wed, 6 Apr 2016 15:42:55 -0500 Message-ID: Subject: Does ZFS or UFS classify FS Metatada I/O requests with specific BIO_META like flag? To: freebsd-fs@freebsd.org Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.21 X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Apr 2016 20:43:15 -0000 Linux file systems pass down a metadata flag with block i/o requests so that the device driver below the file system have this information. This flag could be set on those block I/O requests that the file system issues to file system metadata information like FS inodes, journal , block allocation bitmaps etc. on the disk. Examples: 1) Ext3: This thread here : http://lists.linuxfoundation.org/pipermail/containers/2009-April/017126.html says ext3 file system sets this flag on metadata i/o requests so that it is prioritized over data i/o requests in the I/O controller for the disk. 2) Ext4: This thread tells how ext4 tags all journal i/o with the metadata flag : http://www.spinics.net/lists/linux-ext4/msg18213.html 3) XFS: This thread says XFS file system tags metadata I/O requests for better merging: http://oss.sgi.com/pipermail/xfs/2009-November/004631.html I want to know if the FreeBSD filesystem UFS and ZFS set any such flag. >From a skim through the source code, it does not seem so because the bio structure itself does not have any such flag in the first place : http://fxr.watson.org/fxr/source/sys/bio.h?v=FREEBSD10#L143,144 I approciate any help regarding this. Thanks, Leo