Bug 9560 - drop-cache option
Summary: drop-cache option
Status: RESOLVED WONTFIX
Alias: None
Product: rsync
Classification: Unclassified
Component: core (show other bugs)
Version: 3.0.9
Hardware: All Linux
: P5 normal (vote)
Target Milestone: ---
Assignee: Wayne Davison
QA Contact: Rsync QA Contact
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2013-01-13 16:59 UTC by Florent CARRÉ
Modified: 2015-06-17 10:41 UTC (History)
0 users

See Also:

Attachments
fadvice without effect on remote (16.27 KB, patch)
2015-06-17 10:39 UTC, Michele Dionisio 		no flags Details
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Description Florent CARRÉ 2013-01-13 16:59:13 UTC 
Hello,

Please integrate --drop-cache option in your upstream.
It should allow to avoid filling up the io cache with the copied data.

The current behavior pushes the cached data of other process out of the memory 
and slows down the system as the ram gets filled up.

For exemple, I use rsync without this patch, rsync use 7GB of ram and when it's finished, cache ram is always used.

When I use rsync with this patch, rsync use 7GB of ram but when it's finished, cache ram is removed and avoid an unnecessary swap.

Thanks.

Website of the patch : http://insights.oetiker.ch/linux/fadvise/
Patch file : http://tobi.oetiker.ch/patches/rsync-3.0.9-2-fadvise.patch
Comment 1 michael+samba 2013-04-20 17:30:31 UTC 
I hate to say “me too”, but I would really like to see this. Is there anything I can do to help make this happen? As you can see at http://tobi.oetiker.ch/patches/, the patch is maintained since 2007!
Comment 2 Frits 2013-07-17 10:29:33 UTC 
"me too"
yes , this would be usefull. Filling up memory with cache is not always usefull.
Comment 3 Wayne Davison 2013-12-25 23:13:57 UTC 
Since the patch is very linux-specific and overly klugy, it is better handled by a general-purpose (linux-specific) wrapper that can be used with any copy utility.

I'd suggest checking into this utility:

https://github.com/Feh/nocache

I've compiled/installed it and done some basic testing, and it seems to do a good job of issuing the fadvise64() calls on the files rsync opens.

Some examples:

nocache rsync -aiv --rsync-patch='nocache rsync' some-host:/src/ /dest/
nocache rsync --daemon
Comment 4 Wayne Davison 2013-12-25 23:15:46 UTC 
> nocache rsync -aiv --rsync-patch='nocache rsync' some-host:/src/ /dest/

That was supposed to be --rsync-path=...
Comment 5 Michele Dionisio 2015-06-17 10:39:57 UTC 
Created attachment 11169 [details]
fadvice without effect on remote
Comment 6 Michele Dionisio 2015-06-17 10:41:22 UTC 
Hi, I'm testing the patch on 3.1.1 on an embedded device with swapless linux.

The patch works perfect on my application but to avoid to apply the patch also on the remote side (where I have no control) I have saparated the new command line option --drop-cache in 2:
--drop-cache           that works local
--remote-drop-cache    that works on remote

I think that the patch is more or less mandatory on embedded linux machine to avoid oomkill from not o well tuned kernel and to increase general performance.

regards, and many thanks