From: Anna Fuchs <anna.fuchs@informatik.uni-hamburg.de>
To: lustre-devel@lists.lustre.org
Subject: [lustre-devel] Request arc buffer, zerocopy
Date: Thu, 13 Jun 2019 13:54:47 +0200 [thread overview]
Message-ID: <1560426887.3392.0@informatik.uni-hamburg.de> (raw)
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
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next reply other threads:[~2019-06-13 11:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-13 11:54 Anna Fuchs [this message]
2019-06-13 17:26 ` [lustre-devel] Request arc buffer, zerocopy Andreas Dilger
2019-06-26 13:11 ` Anna Fuchs
2019-06-27 18:13 ` Matthew Ahrens
2019-06-28 9:50 ` Anna Fuchs
2019-07-05 18:15 ` Matthew Ahrens
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