https://jira.whamcloud.com This file is an XML representation of an issue en-us 9.4.14 940014 05-12-2023 https://jira.whamcloud.com/browse/LU-10885 Lustre <p>We should consider to enable the <tt>flock</tt> mount option by default, while still allowing <tt>localflock</tt> and <tt>noflock</tt> options for users that do not want this functionality.  From looking at issues reported on <a href="http://stackexchange.com/" class="external-link" target="_blank" rel="nofollow noopener">http://stackexchange.com/</a> and others, it seems that the lack of <tt>flock</tt> functionality by default is an obstacle for many users to use databases on top of Lustre.</p> <p>If the users are <em>not</em> using <tt>flock</tt> functionality, I don't think this adds any overhead, and if they <em>are</em> using this functionality then they want it enabled in any case.</p> LU-10885

enable flock by default

Improvement Minor Resolved Fixed Patrick Farrell Andreas Dilger easy Fri, 6 Apr 2018 04:11:14 +0000 Thu, 31 Aug 2023 06:39:09 +0000 Tue, 19 Feb 2019 06:04:41 +0000 Lustre 2.13.0 Lustre 2.12.3 0 9 <p>I would offer one further thought - I've talked to people a few times who said "oh localflock makes the not supported message go away, that's fine, I'll run my app like that", without any idea what they were doing, risking incorrect operation in their multi-node app.  "flock" on by default makes perfect sense to me.  (Cray has added it everywhere years and years now.)</p> <p>Andreas Dilger (andreas.dilger@intel.com) uploaded a new patch: <a href="https://review.whamcloud.com/32091" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/32091</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-10885" title="enable flock by default" class="issue-link" data-issue-key="LU-10885"><del>LU-10885</del></a> llite: enable flock mount option by default<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: 1<br/> Commit: 40cf09afb13c6c773ec6781a54059c3472c7f15d</p> <p>Andreas Dilger (andreas.dilger@intel.com) uploaded a new patch: <a href="https://review.whamcloud.com/32092" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/32092</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-10885" title="enable flock by default" class="issue-link" data-issue-key="LU-10885"><del>LU-10885</del></a> tests: clean up flocks_test code style<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: 1<br/> Commit: 49e278280cb133a2b1b7db1debe1cd93a9fcb967</p> <p>Oleg Drokin (green@whamcloud.com) merged in patch <a href="https://review.whamcloud.com/32092/" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/32092/</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-10885" title="enable flock by default" class="issue-link" data-issue-key="LU-10885"><del>LU-10885</del></a> tests: fix up flocks_test bugs and code style<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: <br/> Commit: 3ce41b7168f7a3b5bacb5ae35f278dce4a994fae</p> <p>Oleg Drokin (green@whamcloud.com) merged in patch <a href="https://review.whamcloud.com/32091/" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/32091/</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-10885" title="enable flock by default" class="issue-link" data-issue-key="LU-10885"><del>LU-10885</del></a> llite: enable flock mount option by default<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: <br/> Commit: 3613af3e15cbc6091e3a16c8caeb1307be2d91f6</p> <p>Landed for 2.13</p> <p>Andreas Dilger (adilger@whamcloud.com) uploaded a new patch: <a href="https://review.whamcloud.com/34987" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/34987</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-10885" title="enable flock by default" class="issue-link" data-issue-key="LU-10885"><del>LU-10885</del></a> llite: enable flock mount option by default<br/> Project: fs/lustre-release<br/> Branch: b2_12<br/> Current Patch Set: 1<br/> Commit: 20ed66f1a6aac7623185da70da20950d22f4c666</p> <p>Oleg Drokin (green@whamcloud.com) merged in patch <a href="https://review.whamcloud.com/34987/" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/34987/</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-10885" title="enable flock by default" class="issue-link" data-issue-key="LU-10885"><del>LU-10885</del></a> llite: enable flock mount option by default<br/> Project: fs/lustre-release<br/> Branch: b2_12<br/> Current Patch Set: <br/> Commit: 16fb13eb386380a4eb46b7e016a66cb38a01f54f</p> <p>How this fit with this paragraph from Lustre wiki:</p> <blockquote><p><tt>flock</tt>: enable support for cluster-wide, coherent file locks. Must be applied to the <tt>mount</tt> commands for all clients that will be accessing common data requiring lock functionality. Cluster-wide locking <b>will have a detrimental impact on file system performance, and should only be enabled when absolutely required</b>. For some applications, the locking is only necessary on a sub-set of nodes. For example, the CTDB cluster framework used by Samba to provide a parallel, high-availability SMB gateway, relies on locking of a shared file when coordinating cluster start-up and recovery. However, only the CTDB nodes need to mount the Lustre file system with the <tt>flock</tt> option. This is an example of application or domain-specific lock requirements.</p></blockquote> <p>If you really think there is very limited performance impact, we should probably revise this wiki page.</p> <p>Oh, jeez - I'm not sure when that was written, but it's completely wrong.  It has no measurable impact on performance at all, unless you've got an app that ends up contending those locks between nodes, in which case <b>it is asking for mutual exclusion</b>, and we are only following its requests.  The only case where you'd see a performance hit is in the case of an app making heavy use of locks it doesn't need.  (I am not considering the case where the app makes heavy use of the locks for good reason.  In that case, it needs them for correct operation.)</p> <p><a href="https://jira.whamcloud.com/secure/ViewProfile.jspa?name=degremoa" class="user-hover" rel="degremoa">degremoa</a>, can you link the wiki page or clean it up yourself?  It's just totally wrong.</p> <p>Here is the page: <a href="http://wiki.lustre.org/Mounting_a_Lustre_File_System_on_Client_Nodes" class="external-link" target="_blank" rel="nofollow noopener">http://wiki.lustre.org/Mounting_a_Lustre_File_System_on_Client_Nodes</a></p> <p>Probably better you fix it with the wording you think is appropriate.</p> <p> </p> <p>For my own knowledge, I've never looked at how flock is implemented, but enabling flock does not change at all how locking is working for any other Lustre resources? This only has impact for users explicitly calling flock on their files?</p> <p>Correct - flock is an independent type of MDT lock (it's sort of like if there was a flock bit in the IBITS bit set, but it's not implemented that way), and flocks only interact with other flocks.  So only for those users.  They don't interact at all with other locks - Don't conflict, etc.</p> <p>I'll see if I can still edit the wiki.</p> <p>The flock locks are implemented via DLM on the MDS, but in a separate lock namespace from IBITS locks used for regular files. They are only used of flock is requested by the application, so should have no impact if the application is not using this feature. </p> <p>Thanks a lot for the explanations!</p> <p>Thank you for pointing out the wiki - I've updated it to give users a strong push towards 'flock'.  (localflock has always seemed like a way for ambitious users to corrupt their data)</p> <p>One note: I don't actually know when we switched from whatever flock implementation had a performance cost, but it was a <b>long</b> time ago, so I just settled on "2.x is fine".  (It's definitely true of 2.4/2.5, as well as at least the Seagate 2.1, so I'm pretty sure it's correct.)</p> <p>"Laura Hild &lt;lsh@jlab.org&gt;" uploaded a new patch: <a href="https://review.whamcloud.com/c/fs/lustre-release/+/51948" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/c/fs/lustre-release/+/51948</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-10885" title="enable flock by default" class="issue-link" data-issue-key="LU-10885"><del>LU-10885</del></a> docs: note flock now being enabled by default<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: 1<br/> Commit: 10701dd9101831bbe9521705d2a3754560eaa920</p> <p>"Oleg Drokin &lt;green@whamcloud.com&gt;" merged in patch <a href="https://review.whamcloud.com/c/fs/lustre-release/+/51948/" class="external-link" target="_blank" rel="nofollow noopener">https://review.whamcloud.com/c/fs/lustre-release/+/51948/</a><br/> Subject: <a href="https://jira.whamcloud.com/browse/LU-10885" title="enable flock by default" class="issue-link" data-issue-key="LU-10885"><del>LU-10885</del></a> docs: note flock now being enabled by default<br/> Project: fs/lustre-release<br/> Branch: master<br/> Current Patch Set: <br/> Commit: b557fb21c8dfa676fd4ec528fed3d8ea17bc665f</p> Related LU-8069 LU-12348 Development Rank 1|hzzvdb: Rank (Obsolete) 9223372036854775807