Re: [RFC 09/15] PM / Hibernate: user, implement user_ops writer

Rafael J. Wysocki
2010-03-31T20:29:18Z

On Wednesday 31 March 2010, Jiri Slaby wrote:
> On 03/30/2010 10:50 PM, Rafael J. Wysocki wrote:
> > So, I definitely would like to see numbers.
>
> With the patch attached, I get similar results for
> uncompressed image -> user.c -> s2disk (compress+threads)
> compressed image -> user.c -> s2disk (none of compress+threads)
>
> BUT note that there are differences in pages _copied_ in the "user.c ->
> s2disk" phase. Compression was about 40 %. So in the former case 100000
> pages went through and in the latter one only ~ 38000. So presumably
> there will be savings if the pages are compressed in the kernel in the
> save-image phase instead of in userspace.
>
> I'll test (after I hack that up) also the case of image compression when
> saving the image and let you know.
>
> It was tested on a machine with openSUSE factory with init 5 with KDE 4.
> The memory consumption was ~ 400M (100000 pages) after boot every time.
> Hibernation lasted 12-13s in both cases.

So that's pretty much the same and I don't think feeding compressed images to
s2disk is not worth the effort. Let's assume s2disk will always receive a raw
image (that will make it backwards compatible too).

Rafael