From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anna Fuchs Date: Thu, 13 Jun 2019 13:54:47 +0200 Subject: [lustre-devel] Request arc buffer, zerocopy Message-ID: <1560426887.3392.0@informatik.uni-hamburg.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org Dear all, in osd-zfs/osd_io.c:osd_bufs_get_write you can find a comment regarding zerocopy: /* * currently only full blocks are subject to zerocopy approach: * so that we're sure nobody is trying to update the same block */ Whenever a block to be written is full, an arc buffer is requested, otherwise alloc_page. I do not really understand the conclusion. Why and how do full blocks prevent updates? And put it differently - why not to try zerocopy for not full blocks? What could happen if I tried to request an arc buffer for e.g. a block with missing last page? I would be greateful for details. Best regards Anna -------------- next part -------------- An HTML attachment was scrubbed... URL: