From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anton Blanchard Subject: [PATCH] IB/ehca: Reduce number of spin_lock/spin_unlocks in ehca_poll_eqs Date: Fri, 27 Nov 2009 14:13:20 +1100 Message-ID: <20091127031320.GV32182@kryten> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Hoang-Nam Nguyen , Christoph Raisch , Stefan Roscher , Alexander Schmidt , Joachim Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org ftrace function_graph shows ehca_poll_eqs taking and dropping a spinlock a lot: 16) | .ehca_poll_eqs() { 16) 0.492 us | ._spin_lock(); 16) 0.504 us | ._spin_lock_irqsave(); 16) 0.502 us | ._spin_unlock_irqrestore(); 16) 0.490 us | ._spin_lock_irqsave(); 16) 0.488 us | ._spin_unlock_irqrestore(); 16) 0.488 us | ._spin_lock_irqsave(); 16) 0.488 us | ._spin_unlock_irqrestore(); 16) 0.490 us | ._spin_lock_irqsave(); 16) 0.492 us | ._spin_unlock_irqrestore(); Since it's all the same spinlock, we can just take and drop it once. Signed-off-by: Anton Blanchard --- Index: linux.trees.git/drivers/infiniband/hw/ehca/ehca_main.c =================================================================== --- linux.trees.git.orig/drivers/infiniband/hw/ehca/ehca_main.c 2009-11-27 10:17:29.000000000 +1100 +++ linux.trees.git/drivers/infiniband/hw/ehca/ehca_main.c 2009-11-27 10:19:08.000000000 +1100 @@ -957,15 +957,17 @@ void ehca_poll_eqs(unsigned long data) int max = 3; volatile u64 q_ofs, q_ofs2; unsigned long flags; + spin_lock_irqsave(&eq->spinlock, flags); + q_ofs = eq->ipz_queue.current_q_offset; - spin_unlock_irqrestore(&eq->spinlock, flags); do { - spin_lock_irqsave(&eq->spinlock, flags); q_ofs2 = eq->ipz_queue.current_q_offset; - spin_unlock_irqrestore(&eq->spinlock, flags); max--; } while (q_ofs == q_ofs2 && max > 0); + + spin_unlock_irqrestore(&eq->spinlock, flags); + if (q_ofs == q_ofs2) ehca_process_eq(shca, 0); } -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html