From patchwork Mon Feb 1 06:32:51 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anton Blanchard X-Patchwork-Id: 44161 X-Patchwork-Delegate: benh@kernel.crashing.org Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from bilbo.ozlabs.org (localhost [127.0.0.1]) by ozlabs.org (Postfix) with ESMTP id 700DFB8001 for ; Mon, 1 Feb 2010 17:37:31 +1100 (EST) Received: by ozlabs.org (Postfix, from userid 1010) id 8F8EBB7DCB; Mon, 1 Feb 2010 17:37:14 +1100 (EST) Date: Mon, 1 Feb 2010 17:32:51 +1100 From: Anton Blanchard To: benh@kernel.crashing.org Subject: [PATCH 2/7] powerpc: Reduce footprint of xics_ipi_struct Message-ID: <20100201063251.GU2996@kryten> References: <20100201063023.GT2996@kryten> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20100201063023.GT2996@kryten> User-Agent: Mutt/1.5.20 (2009-06-14) Cc: linuxppc-dev@lists.ozlabs.org X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Right now we allocate a cacheline sized NR_CPUS array for xics IPI communication. Use DECLARE_PER_CPU_SHARED_ALIGNED to put it in percpu data in its own cacheline since it is written to by other cpus. On a kernel with NR_CPUS=1024, this saves quite a lot of memory: text data bss dec hex filename 8767779 2944260 1505724 13217763 c9afe3 vmlinux.irq_cpustat 8767555 2813444 1505724 13086723 c7b003 vmlinux.xics A saving of around 128kB. Signed-off-by: Anton Blanchard Index: linux-cpumask/arch/powerpc/platforms/pseries/xics.c =================================================================== --- linux-cpumask.orig/arch/powerpc/platforms/pseries/xics.c 2010-02-01 17:28:56.980961887 +1100 +++ linux-cpumask/arch/powerpc/platforms/pseries/xics.c 2010-02-01 17:29:00.980963118 +1100 @@ -514,15 +514,13 @@ static void __init xics_init_host(void) /* * XICS only has a single IPI, so encode the messages per CPU */ -struct xics_ipi_struct { - unsigned long value; - } ____cacheline_aligned; - -static struct xics_ipi_struct xics_ipi_message[NR_CPUS] __cacheline_aligned; +static DEFINE_PER_CPU_SHARED_ALIGNED(unsigned long, xics_ipi_message); static inline void smp_xics_do_message(int cpu, int msg) { - set_bit(msg, &xics_ipi_message[cpu].value); + unsigned long *tgt = &per_cpu(xics_ipi_message, cpu); + + set_bit(msg, tgt); mb(); if (firmware_has_feature(FW_FEATURE_LPAR)) lpar_qirr_info(cpu, IPI_PRIORITY); @@ -548,25 +546,23 @@ void smp_xics_message_pass(int target, i static irqreturn_t xics_ipi_dispatch(int cpu) { + unsigned long *tgt = &per_cpu(xics_ipi_message, cpu); + WARN_ON(cpu_is_offline(cpu)); mb(); /* order mmio clearing qirr */ - while (xics_ipi_message[cpu].value) { - if (test_and_clear_bit(PPC_MSG_CALL_FUNCTION, - &xics_ipi_message[cpu].value)) { + while (*tgt) { + if (test_and_clear_bit(PPC_MSG_CALL_FUNCTION, tgt)) { smp_message_recv(PPC_MSG_CALL_FUNCTION); } - if (test_and_clear_bit(PPC_MSG_RESCHEDULE, - &xics_ipi_message[cpu].value)) { + if (test_and_clear_bit(PPC_MSG_RESCHEDULE, tgt)) { smp_message_recv(PPC_MSG_RESCHEDULE); } - if (test_and_clear_bit(PPC_MSG_CALL_FUNC_SINGLE, - &xics_ipi_message[cpu].value)) { + if (test_and_clear_bit(PPC_MSG_CALL_FUNC_SINGLE, tgt)) { smp_message_recv(PPC_MSG_CALL_FUNC_SINGLE); } #if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC) - if (test_and_clear_bit(PPC_MSG_DEBUGGER_BREAK, - &xics_ipi_message[cpu].value)) { + if (test_and_clear_bit(PPC_MSG_DEBUGGER_BREAK, tgt)) { smp_message_recv(PPC_MSG_DEBUGGER_BREAK); } #endif