From: Joerg Roedel <joro@8bytes.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <len.brown@intel.com>,
linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/6] PM / Hibernate: Memory bitmap scalability improvements
Date: Mon, 21 Jul 2014 17:55:40 +0200 [thread overview]
Message-ID: <20140721155540.GO30979@8bytes.org> (raw)
In-Reply-To: <20140721143905.GA16454@amd.pavel.ucw.cz>
Hi,
On Mon, Jul 21, 2014 at 04:39:05PM +0200, Pavel Machek wrote:
> So you reduced O(n) to O(n/2 log(n)) ... that's still O(n log(n)), right?
Radix trees have a memory complexity of ~O(n + log(n)). We have an
additional log(n) space requirement for the tree itself, but we linearly
safe memory for each node compared to the old implementation. Since n
beats log(n) at some point there is a point where we need less pages
with the new code than with the old. That break-even point is somewhere
around 32GB of RAM, for smaller sizes we need 2 additional pages at
most.
>
> > You can also modify the above tool to give you some data to plot, then
> > you will also SEE that there is still a linear relationship between RAM
> > size and memory required by the old and new memory bitmap
> > implementation.
>
> I believe radix tree is O(log(N)) per operation, but its memory is
> certainly not linear.
Numbers beat believes.
Joerg
prev parent reply other threads:[~2014-07-21 15:55 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-18 11:57 Joerg Roedel
2014-07-18 11:57 ` [PATCH 1/6] PM / Hibernate: Create a Radix-Tree to store memory bitmap Joerg Roedel
2014-07-19 0:00 ` Rafael J. Wysocki
2014-07-19 7:57 ` Joerg Roedel
2014-07-18 11:57 ` [PATCH 2/6] PM / Hibernate: Add memory_rtree_find_bit function Joerg Roedel
2014-07-18 11:57 ` [PATCH 3/6] PM / Hibernate: Implement position keeping in radix tree Joerg Roedel
2014-07-18 11:57 ` [PATCH 4/6] PM / Hibernate: Iterate over set bits instead of PFNs in swsusp_free() Joerg Roedel
2014-07-18 11:57 ` [PATCH 5/6] PM / Hibernate: Remove the old memory-bitmap implementation Joerg Roedel
2014-07-18 11:57 ` [PATCH 6/6] PM / Hibernate: Touch Soft Lockup Watchdog in rtree_next_node Joerg Roedel
2014-07-18 22:05 ` [PATCH 0/6] PM / Hibernate: Memory bitmap scalability improvements Rafael J. Wysocki
2014-07-19 7:55 ` Joerg Roedel
2014-07-19 10:26 ` Pavel Machek
2014-07-19 11:35 ` Joerg Roedel
2014-07-19 13:49 ` Pavel Machek
2014-07-21 8:32 ` Joerg Roedel
2014-07-21 11:45 ` Pavel Machek
2014-07-21 14:29 ` Joerg Roedel
2014-07-21 14:39 ` Pavel Machek
2014-07-21 15:55 ` Joerg Roedel [this message]
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