Re: uswsusp history lesson [was Re: [Suspend2-devel] Re: swsusp / suspend2 reliability]

[Nigel Cunningham]

Hi.

On Sunday 09 July 2006 04:52, Rafael J. Wysocki wrote:
> Well, I tried really hard to justify the patch that allowed swsusp to
> create bigger images and 10% was the greatest speedup I could get out of it
> and, let me repeat, _with_ compression and async I/O.  I tried to simulate
> different workloads etc., but I couldn't get more than 10% speedup (the
> biggest image I got was as big as 80% of RAM) - counting the time from
> issuing the suspend command to getting back _responsive_ system after
> resume.

Was that 10% speedup on suspend or resume, or both? With LZF, I see 
approximately double the speed with both reading and writing:

nigel@nigel:/usr/src$ sudo cat /sys/power/suspend2/debug_info
Suspend2 debugging info:
- SUSPEND core   : 2.2.7.2
- Kernel Version : 2.6.18-rc1
- Compiler vers. : 4.0
- Attempt number : 4
- Parameters     : 0 25 0 0 0 0
- Overall expected compression percentage: 0.
- Compressor is 'lzf'.
  Compressed 733736960 bytes into 349517344 (52 percent compression).
- Swapwriter active.
  Swap available for image: 244981 pages.
- Filewriter inactive.
- I/O speed: Write 79 MB/s, Read 77 MB/s.
- Extra pages    : -53 used/4000.

Without compression:

nigel@nigel:/usr/src$ sudo cat /sys/power/suspend2/debug_info
Suspend2 debugging info:
- SUSPEND core   : 2.2.7.2
- Kernel Version : 2.6.18-rc1
- Compiler vers. : 4.0
- Attempt number : 5
- Parameters     : 0 25 0 0 0 0
- Overall expected compression percentage: 0.
- Swapwriter active.
  Swap available for image: 244981 pages.
- Filewriter inactive.
- I/O speed: Write 39 MB/s, Read 38 MB/s.
- Extra pages    : -72 used/4000.

On resume, how are managing to keep the speed up? I implemented readahead of 
up to 2000 pages, only waiting on a page if we actually manage to submit the 
next 2000 pages for I/O and the page we're waiting on isn't yet complete. If 
you do something like that, how do you know when I/O is complete on the page 
you want?

Regards,

Nigel
-- 
Nigel, Michelle and Alisdair Cunningham
5 Mitchell Street
Cobden 3266
Victoria, Australia

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