Messages in this thread | | | Subject | Re: VM question (ramfs abuse) | From | Christoph Rohland <> | Date | 06 Feb 2001 10:18:33 +0100 |
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Hi Paul,
On Mon, 5 Feb 2001, set@pobox.com wrote: > Christoph Rohland <cr@sap.com>, on Sun Feb 04, 2001 [10:53:26 AM] said: > @>Paul <set@pobox.com> writes: > @>> I finally managed to coax the cursor over to mutt and quit it. Then things > @>> were instantly fine and I could remove 'blob'. > @>> My question is, why wasnt any swap used during this time? Ramfs > @>> may not have any backing store? > @> > @>Because RAMFS lives in _physical_ ram. Grab my tmpfs patch and you > @>will have ramfs + swapping and accounting. But set a limit (Mount > @>option size) to it before doing anything like > @>'dd if=/dev/zero of=blob' ;-) > @> > Dear Christoph; > > First, thankyou for the reply. Heh. Meant to send to the list, > but got only you. Oh well. > I have been testing tmpfs on 2.4.1. I havent encountered any > problems, but I have a question. (with a limit, the pathological dd worked > just fine :) For fun, I did a > 'time (make dep && make clean && make bzImage)' using 2.2.18, 2.4.1, and > various fs's as /tmp. (reiser, ext2, ramfs, tmpfs) Both using and not > using the -pipe gcc option during the build. > I was somewhat suprised that each time was the same (within, like > 1/10th of a percent)
You probably have to stress some more since the page cache is _very_ effective on Linux. I can bring down a kernel compile on a 8way machine with parallel make from ~44 seconds to ~40 seconds which is a real speedup ;-)
Actually I really doubt a real speed benefit for normal users with tmpfs but there may be other benefits:
- 'add swap on any device and your tmpfs grows' can be really valuable. - Automatic cleanup of /tmp on reboot - No traces of temporary files on backing store may help the crypto people. (But no if you swap that argument is hosed.) - ???
There are some people out there which really wanted to have this and it was a minor task to add the full support to shm fs.
Greetings Christoph
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