RE: [Qemu-devel][PATCH,RFC] Zero cluster dedup

[Laurent Vivier]

Le mercredi 03 septembre 2008 à 06:07 -0700, Shahar Frank a écrit :
> > This is still the L2 table which has to be written each time. Say we
> > have a 64k write, then you could save 15 L2 table writes if qcow_dedup
> > could handle zeroing multiple contiguous clusters at once. This could
> > matter for performance when wiping lots of data.
> 
> You have a good point when it comes to a sequence of zero clusters (the
> L2 writes can be optimized as you wrote above). I will re-implement
> this.

Perhaps you should consider to set the l2_table entry to 0 when there is
no backing file: it avoids some I/O and allows to aggregate free
entries.
(no, I'm not obstinate :-D )

Laurent
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