From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43217) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b4DjJ-0001lR-FM for qemu-devel@nongnu.org; Sat, 21 May 2016 16:42:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b4DjD-0000G8-M8 for qemu-devel@nongnu.org; Sat, 21 May 2016 16:42:36 -0400 Received: from out2-smtp.messagingengine.com ([66.111.4.26]:42819) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b4DjB-0000Ck-AK for qemu-devel@nongnu.org; Sat, 21 May 2016 16:42:31 -0400 From: "Emilio G. Cota" Date: Sat, 21 May 2016 16:42:14 -0400 Message-Id: <1463863336-28760-1-git-send-email-cota@braap.org> Subject: [Qemu-devel] [PATCH 0/2] atomics: fix small RCU perf. regression + update documentation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: QEMU Developers , MTTCG Devel Cc: =?UTF-8?q?Alex=20Benn=C3=A9e?= , Paolo Bonzini , Richard Henderson , Sergey Fedorov Patch 1 fixes a small performance regression introduced when moving our atomics to __atomic primitives. The regression can be measured on RMO architectures (I used aarch64); the effect is very small but consistently measurable: for instance, rcutorture performance degraded by about 0.3%. Patch 2 originates from a recent discussion[1] that led me to look into what guarantees can be assumed from our atomic_read/set implementations. Thanks, Emilio [1] https://lists.gnu.org/archive/html/qemu-devel/2016-05/msg03088.html