From: "H. Peter Anvin" <hpa@zytor.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Mike Travis <travis@sgi.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Andi Kleen <ak@suse.de>
Subject: Re: [PATCH 06/10] x86: reduce memory and stack usage in intel_cacheinfo
Date: Wed, 26 Mar 2008 10:28:56 -0700 [thread overview]
Message-ID: <47EA87D8.8030305@zytor.com> (raw)
In-Reply-To: <20080326171241.GC20016@elte.hu>
Ingo Molnar wrote:
>> The main goal was to avoid allocating 4096 bytes when only 32 would do
>> (characters needed to represent nr_cpu_ids cpus instead of NR_CPUS
>> cpus.) But I'll look at cleaning it up a bit more. It wouldn't have
>> to be a function if CHUNKSZ in cpumask_scnprintf() were visible (or a
>> non-changeable constant.)
>
> well, do we care about allocating 4096 bytes, as long as we also free
> it? It's not like we need to clear all the bytes or something. Am i
> missing something here?
Well, 32 bytes fits on the stack, whereas 4096 bytes requires allocating
a page -- which means either taking the risk of failing or blocking. Of
course, we're doing this for output, which has the same issue.
-hpa
WARNING: multiple messages have this Message-ID (diff)
From: "H. Peter Anvin" <hpa@zytor.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Mike Travis <travis@sgi.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Andi Kleen <ak@suse.de>
Subject: Re: [PATCH 06/10] x86: reduce memory and stack usage in intel_cacheinfo
Date: Wed, 26 Mar 2008 10:28:56 -0700 [thread overview]
Message-ID: <47EA87D8.8030305@zytor.com> (raw)
In-Reply-To: <20080326171241.GC20016@elte.hu>
Ingo Molnar wrote:
>> The main goal was to avoid allocating 4096 bytes when only 32 would do
>> (characters needed to represent nr_cpu_ids cpus instead of NR_CPUS
>> cpus.) But I'll look at cleaning it up a bit more. It wouldn't have
>> to be a function if CHUNKSZ in cpumask_scnprintf() were visible (or a
>> non-changeable constant.)
>
> well, do we care about allocating 4096 bytes, as long as we also free
> it? It's not like we need to clear all the bytes or something. Am i
> missing something here?
Well, 32 bytes fits on the stack, whereas 4096 bytes requires allocating
a page -- which means either taking the risk of failing or blocking. Of
course, we're doing this for output, which has the same issue.
-hpa
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next prev parent reply other threads:[~2008-03-26 17:30 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-25 22:06 [PATCH 00/10] NR_CPUS: third reduction of NR_CPUS memory usage x86-version v2 Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-25 22:06 ` [PATCH 01/10] x86_64: Cleanup non-smp usage of cpu maps v2 Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-26 6:40 ` Ingo Molnar
2008-03-26 6:40 ` Ingo Molnar
2008-03-26 16:11 ` Mike Travis
2008-03-26 16:11 ` Mike Travis
2008-04-07 20:36 ` Mike Travis
2008-04-07 21:32 ` Ingo Molnar
2008-03-25 22:06 ` [PATCH 02/10] init: move setup of nr_cpu_ids to as early as possible v2 Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-26 6:27 ` Ingo Molnar
2008-03-26 6:27 ` Ingo Molnar
2008-03-26 15:43 ` Mike Travis
2008-03-26 15:43 ` Mike Travis
2008-03-26 17:09 ` Ingo Molnar
2008-03-26 17:09 ` Ingo Molnar
2008-03-26 18:22 ` Mike Travis
2008-03-26 18:22 ` Mike Travis
2008-03-25 22:06 ` [PATCH 03/10] cpufreq: change cpu freq arrays to per_cpu variables Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-25 22:06 ` [PATCH 04/10] acpi: change processors from array to per_cpu variable Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-25 22:06 ` [PATCH 05/10] cpumask: Add cpumask_scnprintf_len function Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-25 22:06 ` [PATCH 06/10] x86: reduce memory and stack usage in intel_cacheinfo Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-26 6:50 ` Ingo Molnar
2008-03-26 6:50 ` Ingo Molnar
2008-03-26 15:41 ` Mike Travis
2008-03-26 15:41 ` Mike Travis
2008-03-26 16:13 ` Jeremy Fitzhardinge
2008-03-26 16:13 ` Jeremy Fitzhardinge
2008-03-26 16:27 ` Mike Travis
2008-03-26 16:27 ` Mike Travis
2008-03-26 16:59 ` Jeremy Fitzhardinge
2008-03-26 16:59 ` Jeremy Fitzhardinge
2008-03-26 18:15 ` Mike Travis
2008-03-26 18:15 ` Mike Travis
2008-03-26 17:12 ` Ingo Molnar
2008-03-26 17:12 ` Ingo Molnar
2008-03-26 17:28 ` H. Peter Anvin [this message]
2008-03-26 17:28 ` H. Peter Anvin
2008-03-26 17:35 ` Ingo Molnar
2008-03-26 17:35 ` Ingo Molnar
2008-03-26 18:20 ` Mike Travis
2008-03-26 18:20 ` Mike Travis
2008-03-25 22:06 ` [PATCH 07/10] cpu: change cpu_sys_devices from array to per_cpu variable Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-25 22:06 ` [PATCH 08/10] net: remove NR_CPUS arrays in net/core/dev.c v2 Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-25 22:06 ` [PATCH 09/10] x86: oprofile: remove NR_CPUS arrays in arch/x86/oprofile/nmi_int.c Mike Travis
2008-03-25 22:06 ` Mike Travis
2008-03-26 6:53 ` Ingo Molnar
2008-03-26 6:53 ` Ingo Molnar
2008-03-25 22:07 ` [PATCH 10/10] sched: Remove fixed NR_CPUS sized arrays in kernel_sched.c Mike Travis
2008-03-25 22:07 ` Mike Travis
2008-03-26 6:34 ` [PATCH 00/10] NR_CPUS: third reduction of NR_CPUS memory usage x86-version v2 Ingo Molnar
2008-03-26 6:34 ` Ingo Molnar
2008-03-26 15:48 ` Mike Travis
2008-03-26 15:48 ` Mike Travis
-- strict thread matches above, loose matches on Subject: below --
2008-03-25 2:19 [PATCH 00/10] NR_CPUS: third reduction of NR_CPUS memory usage Mike Travis
2008-03-25 2:20 ` [PATCH 06/10] x86: reduce memory and stack usage in intel_cacheinfo Mike Travis
2008-03-25 2:20 ` Mike Travis
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