From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 18 Jan 2008 21:48:45 +0100 From: Ingo Molnar Subject: Re: [PATCH 4/5] x86: Add config variables for SMP_MAX Message-ID: <20080118204845.GD3079@elte.hu> References: <20080118183011.354965000@sgi.com> <20080118183011.917801000@sgi.com> <200801182104.22486.ioe-lkml@rameria.de> <479108C3.1010800@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <479108C3.1010800@sgi.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Mike Travis Cc: Ingo Oeser , Andrew Morton , Andi Kleen , Christoph Lameter , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: * Mike Travis wrote: > >> +config THREAD_ORDER > >> + int "Kernel stack size (in page order)" > >> + range 1 3 > >> + depends on X86_64_SMP > >> + default "3" if X86_SMP_MAX > >> + default "1" > >> + help > >> + Increases kernel stack size. > >> + > > > > Could you please elaborate, why this is needed and put more info > > about this requirement into this patch description? > > > > People worked hard to push data allocation from stack to heap to > > make THREAD_ORDER of 0 and 1 possible. So why increase it again and > > why does this help scalability? > > > > Many thanks and Best Regards > > > > Ingo Oeser, puzzled a bit :-) > > > The primary problem arises because of cpumask_t local variables. > Until I can deal with these, increasing NR_CPUS to a really large > value increases stack size dramatically. those should be fixed: > Here are the top stack consumers with NR_CPUS = 4k. > > 16392 isolated_cpu_setup > 10328 build_sched_domains > 8248 numa_initmem_init > 4664 cpu_attach_domain > 4104 show_shared_cpu_map > 3656 centrino_target > 3608 powernowk8_cpu_init > 3192 sched_domain_node_span > 3144 acpi_cpufreq_target > 2584 __svc_create_thread > 2568 cpu_idle_wait > 2136 netxen_nic_flash_print > 2104 powernowk8_target > 2088 _cpu_down > 2072 cache_add_dev > 2056 get_cur_freq > 0 acpi_processor_ffh_cstate_probe > 2056 microcode_write > 0 acpi_processor_get_throttling > 2048 check_supported_cpu (and most of that is performance-uncritical.) Ingo -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org