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...enqueue zero page to balloon device")' > > Ballooned pages will be marked as MADV_DONTNEED by the hypervisor and > shouldn't be given to the host ksmd to scan. I find MADV_DONTNEED reference still quite confusing. What do you think about the following wording instead: " Zeroying ballon pages is rather time consuming, especially when a lot of pages are in flight. E.g. 7GB worth of ballooned memory takes 2.8s with __GFP_ZERO while it takes ~491ms without it. The original commit argued that zeroying will help ksmd to merge these pages on the host but this argument is assum...

This patch is a revert of 'commit bb01b64cfab7 ("mm/balloon_compaction.c: enqueue zero page to balloon device")' Ballooned pages will be marked as MADV_DONTNEED by the hypervisor and shouldn't be given to the host ksmd to scan. 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

This patch is a revert of 'commit bb01b64cfab7 ("mm/balloon_compaction.c: enqueue zero page to balloon device")' Ballooned pages will be marked as MADV_DONTNEED by the hypervisor and shouldn't be given to the host ksmd to scan. 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

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

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

...device have random value, they usually cannot be merged. > So enqueue zero pages will resolve this problem. > > Because MADV_DONTNEED depends on host os capability and hypervisor capability, > I prefer to enqueue zero pages to balloon device and made this patch. So why exactly are we zeroying pages (and pay some cost for that) in guest when we do not know what host actually does with them? -- Michal Hocko SUSE Labs