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Re: [Qemu-devel] [PATCH 01/15] atomic: introduce atomic operations
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 01/15] atomic: introduce atomic operations |
Date: |
Wed, 08 Aug 2012 15:49:42 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 |
Il 08/08/2012 15:32, Peter Maydell ha scritto:
>> > 1. GCC atomics look ugly, :) do not provide rmb/wmb, and in some
>> > versions of GCC mb is known to be (wrongly) a no-op.
>> >
>> > 2. glib atomics do not provide mb/rmb/wmb either, and
>> > g_atomic_int_get/g_atomic_int_set are inefficient: they add barriers
>> > everywhere, while it is clearer if you put barriers manually, and you
>> > often do not need barriers in the get side. glib atomics also do not
>> > provide xchg.
> These are arguments in favour of "don't try to use atomic ops" --
> if serious large projects like GCC and glib can't produce working
> efficient implementations for all target architectures, what chance
> do we have?
Well, maybe... but the flaws in both GCC and glib are small in size
(even though large in importance, at least for us) and we can work
around them easily. mb/rmb/wmb is essentially the small set of atomic
operations that we're already using.
Paolo
[Qemu-devel] [PATCH 02/15] qom: using atomic ops to re-implement object_ref, Liu Ping Fan, 2012/08/08
[Qemu-devel] [PATCH 03/15] qom: introduce reclaimer to release obj, Liu Ping Fan, 2012/08/08
- Re: [Qemu-devel] [PATCH 03/15] qom: introduce reclaimer to release obj, Avi Kivity, 2012/08/08
- Re: [Qemu-devel] [PATCH 03/15] qom: introduce reclaimer to release obj, Paolo Bonzini, 2012/08/08
- Re: [Qemu-devel] [PATCH 03/15] qom: introduce reclaimer to release obj, Avi Kivity, 2012/08/08
- Re: [Qemu-devel] [PATCH 03/15] qom: introduce reclaimer to release obj, liu ping fan, 2012/08/09
- Re: [Qemu-devel] [PATCH 03/15] qom: introduce reclaimer to release obj, Paolo Bonzini, 2012/08/09
- Re: [Qemu-devel] [PATCH 03/15] qom: introduce reclaimer to release obj, Avi Kivity, 2012/08/09
- Re: [Qemu-devel] [PATCH 03/15] qom: introduce reclaimer to release obj, liu ping fan, 2012/08/10