Re: New: squid-1.2-SQUIDFS

From: Oskar Pearson <>
Date: Thu, 21 May 1998 16:34:58 +0200


> Since you're essentially writing a custom filesystem, you might want
> to look into making it log-structured. Perhaps a simple fsck as well.

As far as I know there isn't much use making it logging if your
underlying OS doesn't allow your application to specify that your
files are 'written to the actual disk by the time that the system
call returns'. Linux doesn't do this, for example - everything
is cached.

> Although 32-bit systems would be limited to a single file of not more
> than 2G, an option to mmap(2) the swap files would be a performance
> win. (Hmm, an Alpha or UltraSparc, FC/AL controller, couple of dozen
> 18G Cheetahs, devfs, a driver to expose each disk (not just partition)
> as an mmap(2)able character special file, full HTTP/1.1 compliance....
> Now *that* is a cache box!)

You have to be careful with mmaps... if you mmap the file you no
longer just limit the file size to 2G, you limit your overall cache
size to 2G... (at most)

Your maximum memory-mapped size is equal to your maximum segment size.
This means that you couldn't have a 4gig disk with 2 2gig files on
it am mmap them both... you hit the maximum segment size limit.
Of course I may be wrong... though we have discussed this on
squid-bugs previously...

> I hope all these ideas/comments do not come off as overwhelming. I'd
> certainly volunteer to help. (As you might guess, I've been thinking
> along these lines as well....)


"Haven't slept at all. I don't see why people insist on sleeping. You feel
so much better if you don't. And how can anyone want to lose a minute -
a single minute of being alive?"				-- Think Twice
Received on Thu May 21 1998 - 07:38:17 MDT

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