From: Rik van Riel <riel@nl.linux.org>
To: Joseph Pranevich <knight@baltimore.wwaves.com>
Cc: Linux Kernel <linux-kernel@vger.rutgers.edu>,
Linux MM <linux-mm@kvack.org>
Subject: Re: Swap Questions (includes possible bug) - swapfile.c / swap.c
Date: Tue, 11 May 1999 23:30:35 +0200 (CEST) [thread overview]
Message-ID: <Pine.LNX.4.03.9905112321550.226-100000@mirkwood.nl.linux.org> (raw)
In-Reply-To: <Pine.LNX.4.03.9905111114210.19954-100000@baltimore.wwaves.com>
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.
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next parent reply other threads:[~1999-05-11 22:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Pine.LNX.4.03.9905111114210.19954-100000@baltimore.wwaves.com>
1999-05-11 21:30 ` Rik van Riel [this message]
1999-05-12 15:42 ` [PATCH] Re: Swap Questions (includes possible bug) - swapfile.c / swap.c Joseph Pranevich
1999-05-12 10:30 Manfred Spraul
1999-05-12 18:36 ` Stephen C. Tweedie
1999-05-12 19:45 ` Manfred Spraul
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