Lockless pagecache perhaps for 2.6.18?

Lockless pagecache perhaps for 2.6.18?

[Nick Piggin]

Hi,

Would there be any objection to having my lockless pagecache patches
merged into -mm, for a possible mainline merge after 2.6.17 (ie. if/
when the mm hackers feel comfortable with it).

There are now just 3 patches: 15 files, 312 insertions, 81 deletions
for the core changes, including RCU radix-tree. (not counting those
last two I just sent you Andrew (VM_BUG_ON, find_trylock_page))

It is fairly well commented, and not overly complex (IMO) compared
with other lockless stuff in the tree now.

My main motivation is to get more testing and more serious reviews,
rather than trying to clear a fast path into mainline.

Nick

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Re: Lockless pagecache perhaps for 2.6.18?

[Ingo Molnar]

* Nick Piggin <npiggin@suse.de> wrote:

> Would there be any objection to having my lockless pagecache patches 
> merged into -mm, for a possible mainline merge after 2.6.17 (ie. if/ 
> when the mm hackers feel comfortable with it).

i'd love to see it tested more, and then merged. It's really nifty.

	Ingo

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Re: Lockless pagecache perhaps for 2.6.18?

[Christoph Lameter]

On Thu, 23 Mar 2006, Nick Piggin wrote:

> Would there be any objection to having my lockless pagecache patches
> merged into -mm, for a possible mainline merge after 2.6.17 (ie. if/
> when the mm hackers feel comfortable with it).

I'd like to have those in mm. W

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Re: Lockless pagecache perhaps for 2.6.18?

[Hugh Dickins]

On Thu, 23 Mar 2006, Nick Piggin wrote:
> 
> Would there be any objection to having my lockless pagecache patches
> merged into -mm, for a possible mainline merge after 2.6.17 (ie. if/
> when the mm hackers feel comfortable with it).

No objection from me (though I've still to study it).
But the timing should be as suits Andrew and state of -mm tree.

> There are now just 3 patches: 15 files, 312 insertions, 81 deletions
> for the core changes, including RCU radix-tree. (not counting those
> last two I just sent you Andrew (VM_BUG_ON, find_trylock_page))

Sounds reasonable (and I've come to prefer 3 patches to 141).

> It is fairly well commented, and not overly complex (IMO) compared
> with other lockless stuff in the tree now.
> 
> My main motivation is to get more testing and more serious reviews,
> rather than trying to clear a fast path into mainline.

Yes, please let's not presuppose it'll go into 2.6.18:
that will depend on what confidence it acquires in -mm.

Hugh

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Re: Lockless pagecache perhaps for 2.6.18?

[Nigel Cunningham]

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Hi Nick.

On Thursday 23 March 2006 18:11, Nick Piggin wrote:
> Hi,
>
> Would there be any objection to having my lockless pagecache patches
> merged into -mm, for a possible mainline merge after 2.6.17 (ie. if/
> when the mm hackers feel comfortable with it).
>
> There are now just 3 patches: 15 files, 312 insertions, 81 deletions
> for the core changes, including RCU radix-tree. (not counting those
> last two I just sent you Andrew (VM_BUG_ON, find_trylock_page))
>
> It is fairly well commented, and not overly complex (IMO) compared
> with other lockless stuff in the tree now.
>
> My main motivation is to get more testing and more serious reviews,
> rather than trying to clear a fast path into mainline.
>
> Nick

Can I get a pointer to the patches and any docs please? Since I save the page 
cache separately, I'd need a good understanding of the implications of the 
changes.

Regards,

Nigel

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Re: Lockless pagecache perhaps for 2.6.18?

[Nick Piggin]

Nigel Cunningham wrote:

> Can I get a pointer to the patches and any docs please? Since I save the page 
> cache separately, I'd need a good understanding of the implications of the 
> changes.
> 

Hi Nigel,

http://www.kernel.org/pub/linux/kernel/people/npiggin/patches/lockless/2.6.16-rc5/

There are some patches... a lot of them, but only the last 5 in the series
matter (the rest are pretty much in 2.6.16-head).

There is also a small doc on the lockless radix-tree in that directory. I'm in
the process of writing some documentation on the lockless pagecache itself...

You probably don't need to worry too much unless you are testing page_count()
under the tree_lock, held for writing, expecting that to stabilise page_count.
In which case I could have a look at your code and see if it would be a
problem.

Nick

-- 
SUSE Labs, Novell Inc.

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Re: Lockless pagecache perhaps for 2.6.18?

[Nigel Cunningham]

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Hi Nick.

On Monday 27 March 2006 10:43, Nick Piggin wrote:
> Nigel Cunningham wrote:
> > Can I get a pointer to the patches and any docs please? Since I save the
> > page cache separately, I'd need a good understanding of the implications
> > of the changes.
>
> Hi Nigel,
>
> http://www.kernel.org/pub/linux/kernel/people/npiggin/patches/lockless/2.6.
>16-rc5/
>
> There are some patches... a lot of them, but only the last 5 in the series
> matter (the rest are pretty much in 2.6.16-head).
>
> There is also a small doc on the lockless radix-tree in that directory. I'm
> in the process of writing some documentation on the lockless pagecache
> itself...
>
> You probably don't need to worry too much unless you are testing
> page_count() under the tree_lock, held for writing, expecting that to
> stabilise page_count. In which case I could have a look at your code and
> see if it would be a problem.

Thanks.

I'm not far from head now, so guess I have no problems with the rest.

From what you say about the other patches, I think I'm fine as far as the rest 
go too. I was mostly concerned that the modifications might make it possible 
for the lru to start changing while the image is being written. It looks to 
me now like I was being too paranoid (which isn't necessarily a bad thing, is 
it?).

Regards,

Nigel

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