From: Michal Hocko <mhocko@kernel.org>
To: Steven Sistare <steven.sistare@oracle.com>
Cc: "prakash.sangappa" <prakash.sangappa@oracle.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
dave.hansen@intel.com, nao.horiguchi@gmail.com,
akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
khandual@linux.vnet.ibm.com
Subject: Re: [PATCH V2 0/6] VA to numa node information
Date: Mon, 24 Sep 2018 19:14:43 +0200 [thread overview]
Message-ID: <20180924171443.GI18685@dhcp22.suse.cz> (raw)
In-Reply-To: <91988f05-2723-3120-5607-40fabe4a170d@oracle.com>
On Fri 14-09-18 12:01:18, Steven Sistare wrote:
> On 9/14/2018 1:56 AM, Michal Hocko wrote:
[...]
> > Why does this matter for something that is for analysis purposes.
> > Reading the file for the whole address space is far from a free
> > operation. Is the page walk optimization really essential for usability?
> > Moreover what prevents move_pages implementation to be clever for the
> > page walk itself? In other words why would we want to add a new API
> > rather than make the existing one faster for everybody.
>
> One could optimize move pages. If the caller passes a consecutive range
> of small pages, and the page walk sees that a VA is mapped by a huge page,
> then it can return the same numa node for each of the following VA's that fall
> into the huge page range. It would be faster than 55 nsec per small page, but
> hard to say how much faster, and the cost is still driven by the number of
> small pages.
This is exactly what I was arguing for. There is some room for
improvements for the existing interface. I yet have to hear the explicit
usecase which would required even better performance that cannot be
achieved by the existing API.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2018-09-24 17:14 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-12 20:23 [PATCH V2 0/6] VA to numa node information Prakash Sangappa
2018-09-12 20:23 ` [PATCH V2 1/6] Add check to match numa node id when gathering pte stats Prakash Sangappa
2018-09-12 20:24 ` [PATCH V2 2/6] Add /proc/<pid>/numa_vamaps file for numa node information Prakash Sangappa
2018-09-12 20:24 ` [PATCH V2 3/6] Provide process address range to numa node id mapping Prakash Sangappa
2018-09-12 20:24 ` [PATCH V2 4/6] Add support to lseek /proc/<pid>/numa_vamaps file Prakash Sangappa
2018-09-12 20:24 ` [PATCH V2 5/6] File /proc/<pid>/numa_vamaps access needs PTRACE_MODE_READ_REALCREDS check Prakash Sangappa
2018-09-12 20:24 ` [PATCH V2 6/6] /proc/pid/numa_vamaps: document in Documentation/filesystems/proc.txt Prakash Sangappa
2018-09-13 8:40 ` [PATCH V2 0/6] VA to numa node information Michal Hocko
2018-09-13 22:32 ` prakash.sangappa
2018-09-14 0:10 ` Andrew Morton
2018-09-14 0:25 ` Dave Hansen
2018-09-15 1:31 ` Prakash Sangappa
2018-09-14 5:56 ` Michal Hocko
2018-09-14 16:01 ` Steven Sistare
2018-09-14 18:04 ` Prakash Sangappa
2018-09-14 18:04 ` Prakash Sangappa
2018-09-14 19:01 ` Dave Hansen
2018-09-24 17:14 ` Michal Hocko [this message]
2018-11-10 4:48 ` Prakash Sangappa
2018-11-10 4:48 ` Prakash Sangappa
2018-11-26 19:20 ` Steven Sistare
2018-12-18 23:46 ` prakash.sangappa
2018-12-19 20:52 ` Michal Hocko
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