All of lore.kernel.org
 help / color / mirror / Atom feed
From: David Hildenbrand <david@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: David Gibson <david@gibson.dropbear.id.au>,
	dhildenb@redhat.com, imammedo@redhat.com, ehabkost@redhat.com,
	pbonzini@redhat.com, qemu-devel@nongnu.org, qemu-ppc@nongnu.org
Subject: Re: [Qemu-devel] [RFC 1/5] virtio-balloon: Remove unnecessary MADV_WILLNEED on deflate
Date: Mon, 15 Oct 2018 13:14:25 +0200	[thread overview]
Message-ID: <899a7b64-93d0-5636-d15b-c71a250b8a9e@redhat.com> (raw)
In-Reply-To: <20181015063430-mutt-send-email-mst@kernel.org>


>> (And "Expect access in the near future." does not sound like guarantees
>> to me either way)
> 
> Should we be concerned about impact on performance though?

Yes, it really depends on the use case (and most of the time, the memory
won't be directly reused). Let's document it in the commit log just as
you suggest.

> 
> Thinking aloud it might have an impact.  But there is also a benefit.
> Let's document known effects so people know what to look for
> if they see issues?
> 
> 	WILLNEED aggressively faults all memory in, removing it
> 	will cause just as much memory as needed to be allocated on access,
> 	slowing down the CPU at that point but conserving host memory.
> 
> 	With this patch device assignment (e.g. with VFIO) hotplug will take longer
> 	as it needs to allocate all this memory on hotplug.
> 	While this happens all VM is paused right now.


-- 

Thanks,

David / dhildenb

  reply	other threads:[~2018-10-15 11:14 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-12  3:24 [Qemu-devel] [RFC 0/5] Improve balloon handling of pagesizes other than 4kiB David Gibson
2018-10-12  3:24 ` [Qemu-devel] [RFC 1/5] virtio-balloon: Remove unnecessary MADV_WILLNEED on deflate David Gibson
2018-10-12  7:40   ` David Hildenbrand
2018-10-13  6:26     ` David Gibson
2018-10-12 17:41   ` Richard Henderson
2018-10-12 17:59     ` Eric Blake
2018-10-13  6:23     ` David Gibson
2018-10-12 18:05   ` Michael S. Tsirkin
2018-10-15  6:54     ` David Hildenbrand
2018-10-15 10:43       ` Michael S. Tsirkin
2018-10-15 11:14         ` David Hildenbrand [this message]
2018-12-04  4:26         ` David Gibson
2018-10-12  3:24 ` [Qemu-devel] [RFC 2/5] virtio-balloon: Corrections to address verification David Gibson
2018-10-12  7:44   ` David Hildenbrand
2018-10-13  6:25     ` David Gibson
2018-10-12  3:24 ` [Qemu-devel] [RFC 3/5] virtio-balloon: Rework ballon_page() interface David Gibson
2018-10-12  7:46   ` David Hildenbrand
2018-10-13  6:29     ` David Gibson
2018-10-12  3:24 ` [Qemu-devel] [RFC 4/5] virtio-balloon: Use ram_block_discard_range() instead of raw madvise() David Gibson
2018-10-12  3:24 ` [Qemu-devel] [RFC 5/5] virtio-balloon: Safely handle BALLOON_PAGE_SIZE < host page size David Gibson
2018-10-12  8:06   ` David Hildenbrand
2018-10-13  6:40     ` David Gibson
2018-10-15  7:08       ` David Hildenbrand
2018-10-17  3:28         ` David Gibson
2018-10-17  9:56           ` David Hildenbrand
2018-10-23  8:02             ` David Gibson
2018-10-23 15:13               ` David Hildenbrand
2018-10-12  8:32   ` David Hildenbrand
2018-10-13  6:41     ` David Gibson
2018-10-12 17:26 ` [Qemu-devel] [RFC 0/5] Improve balloon handling of pagesizes other than 4kiB Michael S. Tsirkin
2018-10-17  3:31   ` David Gibson

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=899a7b64-93d0-5636-d15b-c71a250b8a9e@redhat.com \
    --to=david@redhat.com \
    --cc=david@gibson.dropbear.id.au \
    --cc=dhildenb@redhat.com \
    --cc=ehabkost@redhat.com \
    --cc=imammedo@redhat.com \
    --cc=mst@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=qemu-devel@nongnu.org \
    --cc=qemu-ppc@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.