[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img conve
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated() |
Date: |
Wed, 15 Jun 2011 13:02:01 +0100 |
On Wed, Jun 15, 2011 at 10:50 AM, Dmitry Konishchev
<address@hidden> wrote:
> On Wed, Jun 15, 2011 at 12:39 PM, Stefan Hajnoczi <address@hidden> wrote:
>> Why is bdrv_get_geometry() slow?
>
> Mmm.. Frankly, I haven't looked so deep, but it is going to be slow at
> least for raw images due to using lseek().
We need to fully understand performance before applying optimizations
on top. Otherwise it is possible to paper over a problem while
leaving the root cause unsolved. Avoiding lseek(2) is very important,
not just for qemu-img but also for running VMs. lseek(2) should only
be invoked if the image is growable/removable.
When I run a VM from a virtio-blk raw image I see no lseek(2) calls.
On the host:
strace -p $pid_of_qemu -f
Inside the guest:
dd if=/dev/vda of=/dev/null iflag=direct
I see pread(2) from the posix-aio-compat.c worker threads but no
lseek(2). The total_sectors cached value is being used.
Does strace(1) show lseek(2) on your host?
Stefan
- [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/08
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/13
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/13
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/14
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/14
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(),
Stefan Hajnoczi <=
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/15
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/16
- Re: [Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Stefan Hajnoczi, 2011/06/17
[Qemu-devel] [PATCH] CPU consumption optimization of 'qemu-img convert' using bdrv_is_allocated(), Dmitry Konishchev, 2011/06/15