From: Peter Xu <peterx@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>,
Auger Eric <eric.auger@redhat.com>,
Alex Williamson <alex.williamson@redhat.com>,
Wei Yang <richardw.yang@linux.intel.com>,
Igor Mammedov <imammedo@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
"Dr . David Alan Gilbert" <dgilbert@redhat.com>
Subject: Re: [PATCH PROTOTYPE 4/6] memory: Extend ram_block_discard_(require|disable) by two discard types
Date: Tue, 20 Oct 2020 16:49:29 -0400 [thread overview]
Message-ID: <20201020204929.GF200400@xz-x1> (raw)
In-Reply-To: <ea4d0acb-7ee5-7a4b-61aa-f139e0cbf585@redhat.com>
On Tue, Oct 20, 2020 at 09:58:34PM +0200, David Hildenbrand wrote:
> I remember there were some !BQL users (but I might be confusing it with
> postcopy code that once used to inhibit the balloon without BQL). Will
> double-check. Simplifying it is certainly a good idea.
>
> (we want to be able to check from virtio-balloon code repeatedly without
> taking a mutex over and over again :) )
Right. Again I've no strong opinion so feel free to keep the codes as wish.
However if we'd go the other way (either BQL or another mutex) IMHO we can
simply read that flag directly without taking mutex. IMHO here the mutex can
be used to protect write concurrency and should be enough. Considering that
this flag should rarely change and it should never flip (e.g., positive would
never go negative, and vise versa), then READ_ONCE() whould be safe enough on
read side (e.g., balloon).
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2020-10-20 20:50 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-24 16:04 [PATCH PROTOTYPE 0/6] virtio-mem: vfio support David Hildenbrand
2020-09-24 16:04 ` [PATCH PROTOTYPE 1/6] memory: Introduce sparse RAM handler for memory regions David Hildenbrand
2020-10-20 19:24 ` Peter Xu
2020-10-20 20:13 ` David Hildenbrand
2020-09-24 16:04 ` [PATCH PROTOTYPE 2/6] virtio-mem: Impelement SparseRAMHandler interface David Hildenbrand
2020-09-24 16:04 ` [PATCH PROTOTYPE 3/6] vfio: Implement support for sparse RAM memory regions David Hildenbrand
2020-10-20 19:44 ` Peter Xu
2020-10-20 20:01 ` David Hildenbrand
2020-10-20 20:44 ` Peter Xu
2020-11-12 10:11 ` David Hildenbrand
2020-11-18 13:04 ` David Hildenbrand
2020-11-18 15:23 ` Peter Xu
2020-11-18 16:14 ` David Hildenbrand
2020-11-18 17:01 ` Peter Xu
2020-11-18 17:37 ` David Hildenbrand
2020-11-18 19:05 ` Peter Xu
2020-11-18 19:20 ` David Hildenbrand
2020-09-24 16:04 ` [PATCH PROTOTYPE 4/6] memory: Extend ram_block_discard_(require|disable) by two discard types David Hildenbrand
2020-10-20 19:17 ` Peter Xu
2020-10-20 19:58 ` David Hildenbrand
2020-10-20 20:49 ` Peter Xu [this message]
2020-10-20 21:30 ` Peter Xu
2020-09-24 16:04 ` [PATCH PROTOTYPE 5/6] virtio-mem: Require only RAM_BLOCK_DISCARD_T_COORDINATED discards David Hildenbrand
2020-09-24 16:04 ` [PATCH PROTOTYPE 6/6] vfio: Disable only RAM_BLOCK_DISCARD_T_UNCOORDINATED discards David Hildenbrand
2020-09-24 19:30 ` [PATCH PROTOTYPE 0/6] virtio-mem: vfio support no-reply
2020-09-29 17:02 ` Dr. David Alan Gilbert
2020-09-29 17:05 ` David Hildenbrand
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