From: Dave Hansen <dave.hansen@intel.com>
To: Fengguang Wu <fengguang.wu@intel.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Linux Memory Management List <linux-mm@kvack.org>,
Huang Ying <ying.huang@intel.com>,
Brendan Gregg <bgregg@netflix.com>,
Peng DongX <dongx.peng@intel.com>,
Liu Jingqi <jingqi.liu@intel.com>,
Dong Eddie <eddie.dong@intel.com>,
kvm@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCH 2/5] [PATCH 2/5] proc: introduce /proc/PID/idle_bitmap
Date: Thu, 6 Sep 2018 07:12:39 -0700 [thread overview]
Message-ID: <71597e5c-8a7c-3a74-5b6d-6293f07f9a34@intel.com> (raw)
In-Reply-To: <20180901124811.530300789@intel.com>
On 09/01/2018 04:28 AM, Fengguang Wu wrote:
> To walk 1TB memory of 4k active pages, it costs 2s vs 15s system
> time to scan the per-task/global idle bitmaps.
To me, that says this interface simply won't work on large systems. 2s
and 15s are both simply unacceptably long.
> OTOH, the per-task idle bitmap is not suitable in some situations:
>
> - not accurate for shared pages
> - don't work with non-mapped file pages
> - don't perform well for sparse page tables (pointed out by Huang Ying)
OK, so we have a new ABI that doesn't work on large systems, consumes
lots of time and resources to query and isn't suitable in quite a few
situations.
next prev parent reply other threads:[~2018-09-06 14:12 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-01 11:28 [RFC][PATCH 0/5] introduce /proc/PID/idle_bitmap Fengguang Wu
2018-09-01 11:28 ` [RFC][PATCH 1/5] [PATCH 1/5] kvm: register in task_struct Fengguang Wu
2018-09-01 11:28 ` [RFC][PATCH 2/5] [PATCH 2/5] proc: introduce /proc/PID/idle_bitmap Fengguang Wu
2018-09-04 19:02 ` Sean Christopherson
2018-09-06 14:12 ` Dave Hansen [this message]
2018-09-01 11:28 ` [RFC][PATCH 3/5] [PATCH 3/5] kvm-ept-idle: HVA indexed EPT read Fengguang Wu
2018-09-04 7:57 ` Nikita Leshenko
2018-09-04 8:12 ` Peng, DongX
2018-09-04 8:15 ` Fengguang Wu
2018-09-01 11:28 ` [RFC][PATCH 4/5] [PATCH 4/5] kvm-ept-idle: EPT page table walk for A bits Fengguang Wu
2018-09-06 14:35 ` Dave Hansen
2018-09-01 11:28 ` [RFC][PATCH 5/5] [PATCH 5/5] kvm-ept-idle: enable module Fengguang Wu
2018-09-04 19:14 ` Sean Christopherson
2018-09-02 8:24 ` [RFC][PATCH 0/5] introduce /proc/PID/idle_bitmap Fengguang Wu
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