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Re: [Qemu-devel] [PATCH] virtio-blk: Avoid zeroing every request struct
From: |
Corentin Chary |
Subject: |
Re: [Qemu-devel] [PATCH] virtio-blk: Avoid zeroing every request structure |
Date: |
Tue, 18 May 2010 21:55:28 +0200 |
On Tue, May 18, 2010 at 9:02 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Tue, May 18, 2010 at 5:37 PM, Corentin Chary
> <address@hidden> wrote:
>> Did you try to profile using calloc in qemu_mallocz instead of malloc +
>> memset ?
>
> No, I didn't try it. I don't see how it could perform on par with not
> clearing memory at all. Something is going to have to clear that
> memory when using memset() or calloc(). Either libc or the kernel (if
> using mmap).
I believe that if the allocation size is large enougth, getting a
zeroed page can be almost free with clever memory management.
Could you try to re-run your test with calloc and see what it does ?
Speeding up all mallocz calls is probably a good idea :)
--
Corentin Chary
http://xf.iksaif.net
- Re: [Qemu-devel] [PATCH] virtio-blk: Avoid zeroing every request structure, (continued)
Re: [Qemu-devel] [PATCH] virtio-blk: Avoid zeroing every request structure, Corentin Chary, 2010/05/18