From: Rik van Riel <riel@redhat.com>
To: Kelley Nielsen <kelleynnn@gmail.com>, jamieliu@google.com
Cc: linux-mm@kvack.org, riel@surriel.com,
opw-kernel@googlegroups.com, hughd@google.com,
akpm@linux-foundation.org, sarah.a.sharp@intel.com
Subject: Re: [RFC v5] mm: prototype: rid swapoff of quadratic complexity
Date: Tue, 01 Apr 2014 15:25:26 -0400 [thread overview]
Message-ID: <533B12A6.9020403@redhat.com> (raw)
In-Reply-To: <20140401051638.GA13715@kelleynnn-virtual-machine>
On 04/01/2014 01:16 AM, Kelley Nielsen wrote:
> The function try_to_unuse() is of quadratic complexity, with a lot of
> wasted effort. It unuses swap entries one by one, potentially iterating
> over all the page tables for all the processes in the system for each
> one.
>
> This new proposed implementation of try_to_unuse simplifies its
> complexity to linear. It iterates over the system's mms once, unusing
> all the affected entries as it walks each set of page tables. It also
> makes similar changes to shmem_unuse.
>
> Improvement
>
> Time took by swapoff on a swap partition containing about 240M of data,
> with about 1.1G free memory and about 520M swap available. Swap
> partition was on a laptop with a hard disk drive (not SSD).
>
> Present implementation....about 13.8s
> Prototype.................about 5.5s
> TODO
>
> * Handle count of unused pages for frontswap.
That should probably wait for a follow-up patch. This patch is big
enough as is.
> Signed-off-by: Kelley Nielsen <kelleynnn@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
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next prev parent reply other threads:[~2014-04-01 20:04 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-01 5:16 [RFC v5] mm: prototype: rid swapoff of quadratic complexity Kelley Nielsen
2014-04-01 19:25 ` Rik van Riel [this message]
2014-04-09 23:22 ` Hugh Dickins
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