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dm log userspace: allow mark requests to piggyback on flush requests
In the cluster evironment, cluster write has poor performance because userspace_flush() has to contact a userspace program (cmirrord) for clear/mark/flush requests. But both mark and flush requests require cmirrord to communicate the message to all the cluster nodes for each flush call. This behaviour is really slow. To address this we now merge mark and flush requests together to reduce the kernel-userspace-kernel time. We allow a new directive, "integrated_flush" that can be used to instruct the kernel log code to combine flush and mark requests when directed by userspace. If not directed by userspace (due to an older version of the userspace code perhaps), the kernel will function as it did previously - preserving backwards compatibility. Additionally, flush requests are performed lazily when only clear requests exist. Signed-off-by: Dongmao Zhang <dmzhang@suse.com> Signed-off-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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Dongmao Zhang
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Mike Snitzer
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Jan 22, 2014
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