From owner-svn-src-head@freebsd.org Tue Aug 8 11:26:04 2017 Return-Path: Delivered-To: svn-src-head@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 B652EDD5298; Tue, 8 Aug 2017 11:26:04 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 82E22815A2; Tue, 8 Aug 2017 11:26:04 +0000 (UTC) (envelope-from avg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id v78BQ3re047572; Tue, 8 Aug 2017 11:26:03 GMT (envelope-from avg@FreeBSD.org) Received: (from avg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id v78BQ3Lr047571; Tue, 8 Aug 2017 11:26:03 GMT (envelope-from avg@FreeBSD.org) Message-Id: <201708081126.v78BQ3Lr047571@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: avg set sender to avg@FreeBSD.org using -f From: Andriy Gapon Date: Tue, 8 Aug 2017 11:26:03 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r322245 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs X-SVN-Group: head X-SVN-Commit-Author: avg X-SVN-Commit-Paths: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs X-SVN-Commit-Revision: 322245 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Aug 2017 11:26:04 -0000 Author: avg Date: Tue Aug 8 11:26:03 2017 New Revision: 322245 URL: https://svnweb.freebsd.org/changeset/base/322245 Log: MFV r322242: 8373 TXG_WAIT in ZIL commit path illumos/illumos-gate@d28671a3b094af696bea87f52272d4c4d89321c7 https://github.com/illumos/illumos-gate/commit/d28671a3b094af696bea87f52272d4c4d89321c7 https://www.illumos.org/issues/8373 The code that writes ZIL blocks uses dmu_tx_assign(TXG_WAIT) to assign a transaction to a transaction group. That seems to be logically incorrect as writing of the ZIL block does not introduce any new dirty data. Also, when there is a lot of dirty data, the call can introduce significant delays into the ZIL commit path, thus affecting all synchronous writes. Additionally, ARC throttling may affect the ZIL writing. Reviewed by: Matthew Ahrens Reviewed by: Prakash Surya Approved by: Dan McDonald Author: Andriy Gapon MFC after: 2 weeks Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zil.c Directory Properties: head/sys/cddl/contrib/opensolaris/ (props changed) Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zil.c ============================================================================== --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zil.c Tue Aug 8 11:25:09 2017 (r322244) +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zil.c Tue Aug 8 11:26:03 2017 (r322245) @@ -985,7 +985,24 @@ zil_lwb_write_start(zilog_t *zilog, lwb_t *lwb, boolea * to clean up in the event of allocation failure or I/O failure. */ tx = dmu_tx_create(zilog->zl_os); - VERIFY(dmu_tx_assign(tx, TXG_WAIT) == 0); + + /* + * Since we are not going to create any new dirty data and we can even + * help with clearing the existing dirty data, we should not be subject + * to the dirty data based delays. + * We (ab)use TXG_WAITED to bypass the delay mechanism. + * One side effect from using TXG_WAITED is that dmu_tx_assign() can + * fail if the pool is suspended. Those are dramatic circumstances, + * so we return NULL to signal that the normal ZIL processing is not + * possible and txg_wait_synced() should be used to ensure that the data + * is on disk. + */ + error = dmu_tx_assign(tx, TXG_WAITED); + if (error != 0) { + ASSERT3S(error, ==, EIO); + dmu_tx_abort(tx); + return (NULL); + } dsl_dataset_dirty(dmu_objset_ds(zilog->zl_os), tx); txg = dmu_tx_get_txg(tx);