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[Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization
From: |
Frediano Ziglio |
Subject: |
[Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization |
Date: |
Tue, 13 Sep 2011 09:53:06 +0200 |
These patches try to trade-off between leaks and speed for clusters
refcounts.
Refcount increments (REF+ or refp) are handled in a different way from
decrements (REF- or refm). The reason it that posting or not flushing
a REF- cause "just" a leak while posting a REF+ cause a corruption.
To optimize REF- I just used an array to store offsets then when a
flush is requested or array reach a limit (currently 1022) the array
is sorted and written to disk. I use an array with offset instead of
ranges to support compression (an offset could appear multiple times
in the array).
I consider this patch quite ready.
To optimize REF+ I mark a range as allocated and use this range to
get new ones (avoiding writing refcount to disk). When a flush is
requested or in some situations (like snapshot) this cache is disabled
and flushed (written as REF-).
I do not consider this patch ready, it works and pass all io-tests
but for instance I would avoid allocating new clusters for refcount
during preallocation.
End speed up is quite visible allocating clusters (more then 20%).
Frediano Ziglio (2):
qcow2: optimize refminus updates
qcow2: ref+ optimization
block/qcow2-refcount.c | 270 +++++++++++++++++++++++++++++++++++++++++++++---
block/qcow2.c | 2 +
block/qcow2.h | 16 +++
3 files changed, 275 insertions(+), 13 deletions(-)
- [Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization,
Frediano Ziglio <=
- [Qemu-devel] [PATCH][RFC][1/2] qcow2: optimize refminus updates, Frediano Ziglio, 2011/09/13
- [Qemu-devel] [PATCH][RFC][2/2] qcow2: ref+ optimization, Frediano Ziglio, 2011/09/13
- Re: [Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization, Kevin Wolf, 2011/09/13
- Re: [Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization, Frediano Ziglio, 2011/09/13
- Re: [Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization, Kevin Wolf, 2011/09/14
- Re: [Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization, Frediano Ziglio, 2011/09/14
- Re: [Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization, Kevin Wolf, 2011/09/14
- Re: [Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization, Frediano Ziglio, 2011/09/14
- Re: [Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization, Frediano Ziglio, 2011/09/15
Re: [Qemu-devel] [PATCH][RFC][0/2] REF+/REF- optimization, Frediano Ziglio, 2011/09/13