From: Simon Jeons <simon.jeons@gmail.com>
To: Shaohua Li <shli@kernel.org>
Cc: lsf-pc@lists.linux-foundation.org, linux-mm@kvack.org
Subject: Re: [LSF/MM TOPIC]swap improvements for fast SSD
Date: Thu, 24 Jan 2013 00:28:47 -0600 [thread overview]
Message-ID: <1359008927.1375.7.camel@kernel> (raw)
In-Reply-To: <20130122065341.GA1850@kernel.org>
On Tue, 2013-01-22 at 14:53 +0800, Shaohua Li wrote:
> Hi,
>
> Because of high density, low power and low price, flash storage (SSD) is a good
> candidate to partially replace DRAM. A quick answer for this is using SSD as
> swap. But Linux swap is designed for slow hard disk storage. There are a lot of
> challenges to efficiently use SSD for swap:
>
> 1. Lock contentions (swap_lock, anon_vma mutex, swap address space lock)
> 2. TLB flush overhead. To reclaim one page, we need at least 2 TLB flush. This
Which 2 TLB flush?
> overhead is very high even in a normal 2-socket machine.
> 3. Better swap IO pattern. Both direct and kswapd page reclaim can do swap,
> which makes swap IO pattern is interleave. Block layer isn't always efficient
> to do request merge. Such IO pattern also makes swap prefetch hard.
> 4. Swap map scan overhead. Swap in-memory map scan scans an array, which is
> very inefficient, especially if swap storage is fast.
> 5. SSD related optimization, mainly discard support
> 6. Better swap prefetch algorithm. Besides item 3, sequentially accessed pages
> aren't always in LRU list adjacently, so page reclaim will not swap such pages
> in adjacent storage sectors. This makes swap prefetch hard.
> 7. Alternative page reclaim policy to bias reclaiming anonymous page.
> Currently reclaim anonymous page is considering harder than reclaim file pages,
> so we bias reclaiming file pages. If there are high speed swap storage, we are
> considering doing swap more aggressively.
> 8. Huge page swap. Huge page swap can solve a lot of problems above, but both
> THP and hugetlbfs don't support swap.
>
> I had some progresses in these areas recently:
> http://marc.info/?l=linux-mm&m=134665691021172&w=2
> http://marc.info/?l=linux-mm&m=135336039115191&w=2
> http://marc.info/?l=linux-mm&m=135882182225444&w=2
> http://marc.info/?l=linux-mm&m=135754636926984&w=2
> http://marc.info/?l=linux-mm&m=135754634526979&w=2
> But a lot of problems remain. I'd like to discuss the issues at the meeting.
>
> Thanks,
> Shaohua
>
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next prev parent reply other threads:[~2013-01-24 6:28 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-22 6:53 [LSF/MM TOPIC]swap improvements for fast SSD Shaohua Li
2013-01-23 7:58 ` Minchan Kim
2013-01-23 19:04 ` Seth Jennings
2013-01-24 1:40 ` Minchan Kim
2013-01-24 8:29 ` Simon Jeons
2013-01-24 2:02 ` Shaohua Li
2013-01-24 7:52 ` Simon Jeons
2013-01-24 9:09 ` Simon Jeons
2013-01-26 4:40 ` Kyungmin Park
2013-01-27 0:26 ` Simon Jeons
2013-01-27 14:18 ` Shaohua Li
2013-01-28 7:37 ` Kyungmin Park
2013-02-01 12:37 ` Kyungmin Park
2013-02-04 4:56 ` Hugh Dickins
2013-02-19 6:15 ` Shaohua Li
2013-02-19 19:41 ` Hugh Dickins
2013-04-05 0:17 ` Simon Jeons
2013-04-05 8:08 ` Minchan Kim
2013-01-23 16:56 ` Seth Jennings
2013-01-24 6:28 ` Simon Jeons [this message]
2013-03-15 9:39 ` Simon Jeons
2013-03-18 10:38 ` Bob Liu
2013-03-19 1:27 ` Shaohua Li
2013-03-19 1:32 ` Simon Jeons
2013-03-19 5:57 ` Shaohua Li
2013-03-19 6:10 ` Simon Jeons
2013-03-19 4:25 ` Wanpeng Li
2013-03-19 4:25 ` Wanpeng Li
2013-04-28 8:12 ` Simon Jeons
[not found] <766b9855-adf5-47ce-9484-971f88ff0e54@default>
2013-01-23 23:05 ` Dan Magenheimer
2013-01-24 2:11 ` Shaohua Li
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