Messages in this thread | | | Subject | Re: [RFC v2 PATCH 0/4] speed up page allocation for __GFP_ZERO | From | David Hildenbrand <> | Date | Wed, 23 Dec 2020 09:41:00 +0100 |
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>> I was rather saying that for security it's of little use IMHO. >> Application/VM start up time might be improved by using huge pages (and >> pre-zeroing these). Free page reporting might be improved by using >> MADV_FREE instead of MADV_DONTNEED in the hypervisor. >> >>> this feature, above all of them, which one is likely to become the >>> most strong one? From the implementation, you will find it is >>> configurable, users don't want to use it can turn it off. This is not >>> an option? >> >> Well, we have to maintain the feature and sacrifice a page flag. For >> example, do we expect someone explicitly enabling the feature just to >> speed up startup time of an app that consumes a lot of memory? I highly >> doubt it. > > In our production environment, there are three main applications have such > requirement, one is QEMU [creating a VM with SR-IOV passthrough device], > anther other two are DPDK related applications, DPDK OVS and SPDK vhost, > for best performance, they populate memory when starting up. For SPDK vhost, > we make use of the VHOST_USER_GET/SET_INFLIGHT_FD feature for > vhost 'live' upgrade, which is done by killing the old process and > starting a new > one with the new binary. In this case, we want the new process started as quick > as possible to shorten the service downtime. We really enable this feature > to speed up startup time for them :)
Thanks for info on the use case!
All of these use cases either already use, or could use, huge pages IMHO. It's not your ordinary proprietary gaming app :) This is where pre-zeroing of huge pages could already help.
Just wondering, wouldn't it be possible to use tmpfs/hugetlbfs ... creating a file and pre-zeroing it from another process, or am I missing something important? At least for QEMU this should work AFAIK, where you can just pass the file to be use using memory-backend-file.
> >> I'd love to hear opinions of other people. (a lot of people are offline >> until beginning of January, including, well, actually me :) ) > > OK. I will wait some time for others' feedback. Happy holidays!
To you too, cheers!
-- Thanks,
David / dhildenb
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