Messages in this thread | | | Date | Wed, 11 Mar 1998 20:00:27 +0100 | From | Pavel Machek <> | Subject | Re: mmap() versus read() |
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Hi!
> bh> On Tue, 10 Mar 1998, Pavel Machek wrote: > bh> [context: paging executables from origin; why not swap?] > >> Ok. Is there easy way to change it? On my system, swap is order of > >> magnitude faster than disk. I would like linux to take advantage of > >> it. > > bh> There isn't an easy way to change it right now, unless you want to give up > bh> the sharing of clean pages, which is a big loss. One option will be to > bh> take a swap backed inode (I'm using such beasts to replace the SysV shm > bh> objects) and use it to 'cache' the executable - this would be easy enough > bh> to accomplish, but could be a potentially heavy user of swap. It does > bh> have the benefit of also caching normal file access... (say, NFS ;-) > > But the problem is when you are using Linux on embedded systems > without any swap (disk) at all. The programs are stored in the FLASH > RAM so the cost of reading a page from the executable is almost zero, > but using a swap area is impossible (no, we don't have 20 Meg RAM for > a RAM swap disk)
I think that nobody is proposing mandatory use of swap as cache. But on some systems, using swap as cache is win (my system, NFS). It is not win in non-networked non-broken systems, so you probably do not have to worry.
Pavel
-- I'm really pavel@atrey.karlin.mff.cuni.cz. Pavel Look at http://atrey.karlin.mff.cuni.cz/~pavel/ ;-).
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