From mboxrd@z Thu Jan 1 00:00:00 1970 From: Amon Ott Subject: Re: OSD deadlock with cephfs client and OSD on same machine Date: Wed, 30 May 2012 08:59:26 +0200 Message-ID: <201205300859.27181.a.ott@m-privacy.de> References: <201205290944.33983.a.ott@m-privacy.de> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from www.m-privacy.de ([85.214.237.71]:56877 "EHLO www.m-privacy.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751979Ab2E3G75 convert rfc822-to-8bit (ORCPT ); Wed, 30 May 2012 02:59:57 -0400 In-Reply-To: Content-Disposition: inline Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Tommi Virtanen Cc: ceph-devel@vger.kernel.org On Tuesday 29 May 2012 wrote Tommi Virtanen: > On Tue, May 29, 2012 at 12:44 AM, Amon Ott wrote= : > > On Linux, if you run OSD on ext4 filesystem, have a cephfs kernel c= lient > > mount on the same system and no syncfs system call (as to be expect= ed > > with libc6 < 2.14 or kernel < 2.6.39), OSD deadlocks in sys_sync().= Only > > reboot recovers the system. > > This is the classic issue of memory pressure needing free memory to b= e > relieved. While syncfs(2) may make the hang less common, I do not > think having syncfs(2) is enough; nothing sort of having a reserved > memory pool guaranteed to be big enough to handle the request will, > and maintaining that solution is hideously complex. AFAIR, when the deadlocks came, there were some GB of the 12 GB RAM sti= ll=20 unused, not even for caching. But it might be a problem with low memory= ,=20 because we are running with 32 Bit. Would it be possible to preallocate a significant amount of RAM for the= =20 purpose of syncing? I would not mind reserving a few 100 MB for that, b= ut=20 deadlocks must not happen in any case. Can the size of the journal give= a=20 hint on how much is needed? Amon Ott --=20 Dr. Amon Ott m-privacy GmbH Tel: +49 30 24342334 Am K=C3=B6llnischen Park 1 Fax: +49 30 24342336 10179 Berlin http://www.m-privacy.de Amtsgericht Charlottenburg, HRB 84946 Gesch=C3=A4ftsf=C3=BChrer: Dipl.-Kfm. Holger Maczkowsky, Roman Maczkowsky GnuPG-Key-ID: 0x2DD3A649 -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html