Change in vdsm[master]: block: add blkdiscard on zero image

ykaul at redhat.com ykaul at redhat.com
Sun Nov 15 20:35:48 UTC 2015


Yaniv Kaul has posted comments on this change.

Change subject: block: add blkdiscard on zero image
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Patch Set 3:

(1 comment)

https://gerrit.ovirt.org/#/c/35631/3/vdsm/storage/blockVolume.py
File vdsm/storage/blockVolume.py:

Line 228:                     
Looking at blkdiscard's man:
-p, --step length
              The number of bytes to discard within one iteration. The default
              is to discard all by one ioctl call.


So for example, let's assume we have 1TB LV to discard - it cannot do it on one IOCTL. What happens? Different storages have:
1. Different number of ranges they can unmap (most support 1 only, this is also what VMware does and I believe Linux kernel's UNMAP. sg_unmap can do multiple ranges)
2. Maximum length of UNMAP (can be found via some VPD page).


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Gerrit-MessageType: comment
Gerrit-Change-Id: I4e059c556c550440727b36b8af8e5dfc29ce2ccb
Gerrit-PatchSet: 3
Gerrit-Project: vdsm
Gerrit-Branch: master
Gerrit-Owner: Federico Simoncelli <fsimonce at redhat.com>
Gerrit-Reviewer: Allon Mureinik <amureini at redhat.com>
Gerrit-Reviewer: Jenkins CI
Gerrit-Reviewer: Nir Soffer <nsoffer at redhat.com>
Gerrit-Reviewer: Tal Nisan <tnisan at redhat.com>
Gerrit-Reviewer: Yaniv Kaul <ykaul at redhat.com>
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