Re: [2.4.17/18pre] VM and swap - it's really unusable

[Aviv Shavit]

late as usual ....

thanks Ken.

Just got to testng rmap-12f on 2.4.17. While I was
able to throw at it more sessions then at the vannila
kernel, it crashed with a kernel panic. Something that
has not happend for main-line .17 nor for .18.

I use the term sessions since the bandwidth I throw at
the machine is more or less a constant flooded
fastether link at 80Mb/s. The more the sessions - the
more the memory used and more files accessed.

18aa works great ! I love seeing how the cached memory
actually is reduced as the number of sessions grow. ;)

I've been trying to isolate what it is in aa that
helps me so. Tried the _vm_ batch - but they didn't
seem to score. 

Perhaps this info helps someone.

Thanks again.

--- Ken Brownfield <[e-mail]> wrote:
> I've been playing with 2.4.18 with the following
> primary patches with
> very good results:
> 
> 	O(1)-K3
> 	Andrew Morton's low-latency and read-latency2
> 	Martin's vmscan patch
> 
> In the past, I've been applying low-latency without
> enabling the CONFIG
> option, silly me.  Why haven't Andrew's low latency
> patches gone into
> 2.4 or 2.5?  Let's pretty please with sugar on top
> and a cherry get
> those into 2.4.19 even if -aa doesn't make it --
> it's making a world of
> difference in the stuff I'm throwing at the kernel,
> and I'm thinking -aa
> and -rmap are giving improvements partially because
> they incorporate
> some of these changes.
> 
> I think adding 10_vm would put the finishing touch
> on bridging the gap until
> 2.5, IMHO.  O(1) would just be the proverbial icing
> on the cake at a later
> stage, since there still seems to be some work left
> to do on it (per-CPU
> stuff?).
> 
> Now if TUX2 would only stop going into 99% CPU mode.
> ;)
> -- 
> Ken.
> [e-mail]
> 
> On Mon, Feb 25, 2002 at 06:09:34PM -0600, Ken
> Brownfield wrote:
> | On Mon, Feb 25, 2002 at 03:51:43AM -0800, Aviv
> Shavit wrote:
> | | Ken Brownfield's A) and B) hit me
> | |
>
regularly(http://www.uwsg.indiana.edu/hypermail/linux/kernel/0201.0/0740.html)
> | | (Thanks Ken for starting this enlightening
> thread and
> | | to all those that contributed)
> | 
> | No problem.  You might be coming in late, but
> nothing's changed. :-/
> | Although the APIC thing might be MPS1.4 related,
> I'm finding.  I don't
> | remember if that thread had my workaround to the
> APIC issue, so I'll
> | attach that if you're feeling adventurous.  Works
> flawlessly for me in
> | production, for the last few months.
> | 
> | | Running software I developed:
> | | - running on 2.4.17
> | | - accessing a large number of files
> | | - 2GB memory
> | | - large multiple partitions - ext2
> | | 
> | | I saw references to patches by Martin and
> | | M.H.vanLeeuwen on this thread. Where can I get
> those
> | | (hopefully with a bit of info) ?
> | 
> | I've attached his patch; hopefully he doesn't
> mind.  His patch is
> | actually similar to code that's in rmap currently.
> | 
> | It does seem to temper the effects of [id]cache
> bloat for some of my
> | more common load patterns.  But even with that
> patch, under VM load the
> | mainline kernel collapses.  For instance, I have a
> large parallel task
> | that takes 5 minutes under -rmap or -aa, but I get
> bored and kill it
> | after 4 *hours* on mainline.  It dips into swap,
> but only by about 50MB.
> | 
> | Also, -aa doesn't seem to make as large an impact
> on shrinking the
> | [id]caches.  I imagine that without returning
> values,
> | shrink_[id]cache_memory() behavior is difficult to
> tune appropriately.
> | 
> | In any case, rmap-12f has been running fine for
> me.  I'm going to create
> | three kernels to distribute in production --
> 2.4.18 more or less
> | vanilla, 2.4.18 with random debugging (thanks
> Andreas) to try to resolve
> | the /dev/random death issue, and
> 2.4.18+O(1)K3+rmap12f.
> | 
> | rmap is a tremendous improvement over mainline --
> really the only data I
> | still need is stability, both of O(1) and rmap. 
> Porting Andrea's 10_vm
> | was a pain the last time I did it, and it didn't
> have all of the
> | positives of rmap.
> | 
> | Clearly I'm not in the majority, though.  While I
> get bitten on a weekly
> | basis by the 2.4 VM, very few other people mention
> it.  Maybe they just
> | assume that it's normal behavior?  Scary.
> | 
> | Anyway, short of the long is that I would suggest
> rmap if you're having
> | problems.  Rmap actually obviates three other
> patches I typically apply.
> | But be aware that rmap is still a bit of a work in
> progress, at least in
> | terms of tuning.
> | 
> | Cheers,
> | -- 
> | Ken.
> | [e-mail]
> | 
> | 
> | | I also saw references to 'rmap' on the 2.4.18
> | | changelog. Is that related ?
> | | 
> | | pls. cc' me on your posts back.
> | | 
> | | Thanks
> | | Aviv
> | | 
> | | "And all this science I don't understand,
> | |       It's just my job five days a week"
> | | Rocket Man, E.J.
> | 
> | 
> | --- linux.virgin/mm/vmscan.c	Mon Dec 31 12:46:25
> 2001
> | +++ linux/mm/vmscan.c	Fri Jan 11 18:03:05 2002
> | @@ -394,9 +394,9 @@
> |  		if (PageDirty(page) &&
> is_page_cache_freeable(page) && page->mapping) {
> |  			/*
> |  			 * It is not critical here to write it only if
> | -			 * the page is unmapped beause any direct
> writer
> | +			 * the page is unmapped because any direct
> writer
> |  			 * like O_DIRECT would set the PG_dirty
> bitflag
> | -			 * on the phisical page after having
> successfully
> | +			 * on the physical page after having
> successfully
> |  			 * pinned it and after the I/O to the page is
> finished,
> |  			 * so the direct writes to the page cannot get
> lost.
> |  			 */
> | @@ -480,11 +480,14 @@
> |  
> |  			/*
> |  			 * Alert! We've found too many mapped pages on
> the
> | -			 * inactive list, so we start swapping out
> now!
> | +			 * inactive list.
> | +			 * Move referenced pages to the active list.
> |  			 */
> | -			spin_unlock(&pagemap_lru_lock);
> | -			swap_out(priority, gfp_mask, classzone);
> | -			return nr_pages;
> | +			if (PageReferenced(page) && !PageLocked(page))
> {
> | +				del_page_from_inactive_list(page);
> | +				add_page_to_active_list(page);
> | +			}
> | +			continue;
> |  		}
> |  
> |  		/*
> | @@ -521,6 +524,9 @@
> |  	}
> |  	spin_unlock(&pagemap_lru_lock);
> |  
> | +	if (max_mapped <= 0 && (nr_pages > 0 || priority
> < DEF_PRIORITY))
> | +		swap_out(priority, gfp_mask, classzone);
> | +
> |  	return nr_pages;
> |  }
> |  
> | -
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