Messages in this thread | | | Date | Tue, 11 May 1999 23:30:35 +0200 (CEST) | From | Rik van Riel <> | Subject | Re: Swap Questions (includes possible bug) - swapfile.c / swap.c |
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On Tue, 11 May 1999, Joseph Pranevich wrote:
> I've been gradually sifting my way through the kernel source and I > have a few minor questions about memory management.
linux-mm@kvack.org (majordomo-managed) http://www.linux.eu.org/Linux-MM/
> 1) swap.c : page clustering?
> else > page_cluster = 4; > > This is fine, but wouldn't it make sense to generalize this, or is > the benifit not as great with larger amounts of ram?
The swapOUT clustering is only done to a maximum of 32 (2^5) pages, so it doesn't make much sense to read in more pages (which are probably unrelated to the current process).
For mmap() reading we might want to switch to a smarter algorithm though. Not with reading in more pages, but with reading in the _next_ area while the program is still busy processing this one. The idea is to have all data in memory just before the process needs it :)
> 2) swapfile.c : sys_swapon() question 1 > > I'm unable to figure out exactly what this code is supposed to be > doing. Can someone help me out here? I don't understand why we set > the blocksize twice or what the funniness is with "filp" > > p->swap_device = swap_dentry->d_inode->i_rdev; > set_blocksize(p->swap_device, PAGE_SIZE);
We do I/O on this device in chunks of PAGE_SIZE.
> filp.f_dentry = swap_dentry; > filp.f_mode = 3; /* read write */
Of course, we want to have our swap device read-write and we mark it with a magic number so no harm will come to it...
> set_blocksize(p->swap_device, PAGE_SIZE);
Hmm, haven't we seen this one before? Stephen?
> I do apologise for the many questions, I'm just trying to get a > feel for the swapping subsystem. I apologise if this is already > documented someplace.
AFAIK it's not yet documented. I'd really appreciate it if you could do that and send me the docs for inclusion on the Linux-MM site...
cheers,
Rik -- Open Source: you deserve to be in control of your data. +-------------------------------------------------------------------+ | Le Reseau netwerksystemen BV: http://www.reseau.nl/ | | Linux Memory Management site: http://www.linux.eu.org/Linux-MM/ | | Nederlandse Linux documentatie: http://www.nl.linux.org/ | +-------------------------------------------------------------------+
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