Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: sync_file_range(SYNC_FILE_RANGE_WRITE) blocks? | Date | Mon, 2 Jun 2008 13:18:25 +0200 |
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On Monday, 2 of June 2008, Hugh Dickins wrote: > On Sun, 1 Jun 2008, Andrew Morton wrote: > > On Mon, 2 Jun 2008 01:00:40 +0200 Pavel Machek <pavel@suse.cz> wrote: > > > > How about this: > > > > > > > > - Add a new SYNC_FILE_RANGE_NON_BLOCKING > > > > > > > > - If userspace set that flag, turn on writeback_control.nonblocking > > > > in __filemap_fdatawrite_range(). > > > > > > > > - test it a lot. > > > > > > Works for me. Is the expectation that I code this? I can certainly > > > provide testing ;-). > > > > Something like this: > > Though this fits very easily into the current kernel implementation, > I don't think it's the right interface for userspace. > > If we do go this kind of a way, then I'd say SYNC_FILE_RANGE_NON_BLOCKING > needs to tell the caller how far it got before giving up, rather than just > success or failure. Why? um, um, because it feels right; and would help > the caller help the kernel by not overloading it with needlessly repeated > loop ranges - any stronger reasons? But sync_file_range() was defined > to return int rather than ssize_t, so that becomes awkward. > > Never mind, I don't think it is the right way anyway. We don't need > additions to the existing sync_file_range() interface, we just need it > to behave as naive people like Pavel and I expected it to behave in the > first place: SYNC_FILE_RANGE_WRITE should be nonblocking (with respect > to queue congestion, and maybe page locking also).
Well, frankly, I'm not sure if we need anything better than we already have. In fact my numbers show that SYNC_FILE_RANGE_WRITE works quite well - please see http://sourceforge.net/mailarchive/message.php?msg_name=200806020122.36193.rjw%40sisk.pl "early writeout" means that SYNC_FILE_RANGE_WRITE is used and the file with the results is attached for convenience.
My interpretation of the results is here: http://sourceforge.net/mailarchive/forum.php?thread_name=200806021238.17100.rjw%40sisk.pl&forum_name=suspend-devel
Thanks, Rafael Labels: W+ - early writeout enabled W- - early writeout disabled C+ - compression enabled C- - compression disabled E+ - encryption enabled E- - encryption disabled T+ - threads enabled T- - threads disabled
The numbers are speed values in MB/s.
Box 1 (Single-core, Athlon 64 3000+ 1.8 GHz, 1 MB L2 cache, 1.5 GB RAM)
W-C-E-T- W+C-E-T- W-C+E-T- W+C+E-T- Write: 26.2 27.4 46.5 78.6 Read: 27.5 27.5 83.5 83.8
W-C-E+T- W+C-E+T- W-C+E+T- W+C+E+T- Write: 15.6 19.1 28.4 38.7 Read: 18.0 18.1 46.1 46.2
W-C-E+T+ W+C-E+T+ W-C+E+T+ W+C+E+T+ Write: N/A N/A 27.9 37.5 Read: N/A N/A 46.4 46.4
For compressed images the compression ratio was approx. 0.30
Box 2 (Dual-core, Turion X2 TL-60 2 GHz, 2 x 512 KB L2 cache, 2 GB RAM)
W-C-E-T- W+C-E-T- W-C+E-T- W+C+E-T- Write: 31.9 34.1 42.7 74.5 Read: 33.0 32.9 79.8 80.1
W-C-E+T- W+C-E+T- W-C+E+T- W+C+E+T- Write: 16.7 22.0 23.9 34.0 Read: 22.2 22.2 47.6 47.9
W-C-E+T+ W+C-E+T+ W-C+E+T+ W+C+E+T+ Write: 16.4 22.2 34.7 57.2 Read: 22.2 22.1 47.9 48.0
For compressed images the compression ratio was approx. 0.40
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