Messages in this thread | | | Date | Mon, 31 Jul 2017 15:41:49 +0800 | From | Wei Wang <> | Subject | Re: [PATCH] mm: don't zero ballooned pages |
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On 07/31/2017 02:55 PM, Michal Hocko wrote: > On Mon 31-07-17 12:13:33, Wei Wang wrote: >> Ballooned pages will be marked as MADV_DONTNEED by the hypervisor and >> shouldn't be given to the host ksmd to scan. > Could you point me where this MADV_DONTNEED is done, please?
Sure. It's done in the hypervisor when the balloon pages are received.
Please see line 40 at https://github.com/qemu/qemu/blob/master/hw/virtio/virtio-balloon.c
> >> Therefore, it is not >> necessary to zero ballooned pages, which is very time consuming when >> the page amount is large. The ongoing fast balloon tests show that the >> time to balloon 7G pages is increased from ~491ms to 2.8 seconds with >> __GFP_ZERO added. So, this patch removes the flag. > Please make it obvious that this is a revert of bb01b64cfab7 > ("mm/balloon_compaction.c: enqueue zero page to balloon device"). > >
Ok, will do.
Best, Wei
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