[ovs-dev] [PATCH] INSTALL: Note about compiler atomics support.
YAMAMOTO Takashi
yamamoto at valinux.co.jp
Wed Jun 4 06:38:17 UTC 2014
> OVS is slow when compiled with pthreads atomics. Add a generic note
> in INSTALL, with a reference to lib/ovs-atomic.h, where a new comment
> provides additional detail.
>
> Signed-off-by: Jarno Rajahalme <jrajahalme at nicira.com>
Acked-by: YAMAMOTO Takashi <yamamoto at valinux.co.jp>
> ---
> INSTALL | 4 ++++
> lib/ovs-atomic.h | 3 +++
> 2 files changed, 7 insertions(+)
>
> diff --git a/INSTALL b/INSTALL
> index 5c869b2..7b08172 100644
> --- a/INSTALL
> +++ b/INSTALL
> @@ -28,6 +28,10 @@ you will need the following software:
> analysis and thread-safety checks. For Ubuntu, there are
> nightly built packages available on clang's website.
>
> + * While OVS may be compatible with other compilers, optimal
> + support for atomic operations may be missing, making OVS
> + very slow (see lib/ovs-atomic.h).
> +
> - libssl, from OpenSSL, is optional but recommended if you plan to
> connect the Open vSwitch to an OpenFlow controller. libssl is
> required to establish confidentiality and authenticity in the
> diff --git a/lib/ovs-atomic.h b/lib/ovs-atomic.h
> index c21b7ee..2452846 100644
> --- a/lib/ovs-atomic.h
> +++ b/lib/ovs-atomic.h
> @@ -257,6 +257,9 @@
> #elif HAVE_GCC4_ATOMICS
> #include "ovs-atomic-gcc4+.h"
> #else
> + /* ovs-atomic-pthreads implementation is provided for portability.
> + * It might be too slow for real use because Open vSwitch is
> + * optimized for platforms where real atomic ops are available. */
> #include "ovs-atomic-pthreads.h"
> #endif
> #undef IN_OVS_ATOMIC_H
> --
> 1.7.10.4
>
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