From: Bharata B Rao <bharata@linux.vnet.ibm.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH v2] scsi-disk: add UNMAP limits to block limits VPD page
Date: Sun, 22 Dec 2013 19:56:40 +0530 [thread overview]
Message-ID: <20131222142639.GB3374@in.ibm.com> (raw)
In-Reply-To: <1387720647-10284-1-git-send-email-pbonzini@redhat.com>
On Sun, Dec 22, 2013 at 02:57:27PM +0100, Paolo Bonzini wrote:
> Linux prefers WRITE SAME to UNMAP if the limits are zero, and WRITE
> SAME does not discard anything unless the device can guarantee that
> the resulting block is zero.
>
> Setting the maximum unmap block and descriptor counts to non-zero
> makes Linux choose UNMAP and fixes thin provisioning on glusterfs.
>
> While the maximum unmap block count can have some effect on performance,
> the (suggested) maximum number of descriptors is not particularly
> important so I didn't add a customization option. SCSI drivers are
> used to online firmware updates so I'm not yet adding versioning support
> for SCSI, but we're probably getting close to the point when it's worth
> thinking about it.
>
> Reported-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This patch fixes thin provisioning on gluster.
Tested-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Regards,
Bharata.
prev parent reply other threads:[~2013-12-22 14:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-22 13:57 [Qemu-devel] [PATCH v2] scsi-disk: add UNMAP limits to block limits VPD page Paolo Bonzini
2013-12-22 14:26 ` Bharata B Rao [this message]
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