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author | Mike Snitzer <snitzer@redhat.com> | 2011-08-02 12:32:08 +0100 |
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committer | Alasdair G Kergon <agk@redhat.com> | 2011-08-02 12:32:08 +0100 |
commit | ed8b752bccf2560e305e25125721d2f0ac759e88 (patch) | |
tree | b909fcf21ca7cdda3e7a680b37162212cce99586 /Documentation | |
parent | 772ae5f54d69c38a5e3c4352c5fdbdaff141af21 (diff) | |
download | op-kernel-dev-ed8b752bccf2560e305e25125721d2f0ac759e88.zip op-kernel-dev-ed8b752bccf2560e305e25125721d2f0ac759e88.tar.gz |
dm table: set flush capability based on underlying devices
DM has always advertised both REQ_FLUSH and REQ_FUA flush capabilities
regardless of whether or not a given DM device's underlying devices
also advertised a need for them.
Block's flush-merge changes from 2.6.39 have proven to be more costly
for DM devices. Performance regressions have been reported even when
DM's underlying devices do not advertise that they have a write cache.
Fix the performance regressions by configuring a DM device's flushing
capabilities based on those of the underlying devices' capabilities.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'Documentation')
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