Re: [Qemu-devel] [RFC] qcow2: 2 way to improve performance updating refcount

2011-07-22 Thread Kevin Wolf
Am 21.07.2011 18:17, schrieb Frediano Ziglio: Hi, after a snapshot is taken currently many write operations are quite slow due to - refcount updates (decrement old and increment new ) - cluster allocation and file expansion - read-modify-write on partial clusters I found 2 way to

Re: [Qemu-devel] [RFC] qcow2: 2 way to improve performance updating refcount

2011-07-22 Thread Frediano Ziglio
2011/7/22 Kevin Wolf kw...@redhat.com: Am 21.07.2011 18:17, schrieb Frediano Ziglio: Hi,   after a snapshot is taken currently many write operations are quite slow due to - refcount updates (decrement old and increment new ) - cluster allocation and file expansion - read-modify-write on

Re: [Qemu-devel] [RFC] qcow2: 2 way to improve performance updating refcount

2011-07-22 Thread Kevin Wolf
Am 22.07.2011 11:13, schrieb Frediano Ziglio: 2011/7/22 Kevin Wolf kw...@redhat.com: Am 21.07.2011 18:17, schrieb Frediano Ziglio: Hi, after a snapshot is taken currently many write operations are quite slow due to - refcount updates (decrement old and increment new ) - cluster allocation

Re: [Qemu-devel] [RFC] qcow2: 2 way to improve performance updating refcount

2011-07-22 Thread Stefan Hajnoczi
On Fri, Jul 22, 2011 at 10:13 AM, Frediano Ziglio fredd...@gmail.com wrote: 2011/7/22 Kevin Wolf kw...@redhat.com: Am 21.07.2011 18:17, schrieb Frediano Ziglio: Hi,   after a snapshot is taken currently many write operations are quite slow due to - refcount updates (decrement old and

Re: [Qemu-devel] [RFC] qcow2: 2 way to improve performance updating refcount

2011-07-22 Thread Frediano Ziglio
2011/7/22 Stefan Hajnoczi stefa...@gmail.com: On Fri, Jul 22, 2011 at 10:13 AM, Frediano Ziglio fredd...@gmail.com wrote: 2011/7/22 Kevin Wolf kw...@redhat.com: Am 21.07.2011 18:17, schrieb Frediano Ziglio: Hi,   after a snapshot is taken currently many write operations are quite slow due to

Re: [Qemu-devel] [RFC] qcow2: 2 way to improve performance updating refcount

2011-07-22 Thread Stefan Hajnoczi
On Fri, Jul 22, 2011 at 3:21 PM, Frediano Ziglio fredd...@gmail.com wrote: 2011/7/22 Stefan Hajnoczi stefa...@gmail.com: On Fri, Jul 22, 2011 at 10:13 AM, Frediano Ziglio fredd...@gmail.com wrote: 2011/7/22 Kevin Wolf kw...@redhat.com: Am 21.07.2011 18:17, schrieb Frediano Ziglio: Hi,  

[Qemu-devel] [RFC] qcow2: 2 way to improve performance updating refcount

2011-07-21 Thread Frediano Ziglio
Hi, after a snapshot is taken currently many write operations are quite slow due to - refcount updates (decrement old and increment new ) - cluster allocation and file expansion - read-modify-write on partial clusters I found 2 way to improve refcount performance Method 1 - Lazy count Mainly