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nfs-utils inode cache patch

DISCUSSION Simon Peter 4 participants 4 messages Mar 9, 2007 – Mar 13, 2007

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#0 lore raw

Hi Neil,

okay, here's the patch making the kernel cache inode data of exported directories forever, thus avoiding unnecessary disk spin-ups when this data is looked for. It looks correct, works for me and both Bruce and you have been encouraging it. :) Would be great if that could go into nfs-utils.

Thanks,
Simon

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#1 lore raw
Quoted 10 lines · On Friday March 9, [email protected] wrote:

Hi Neil,

okay, here's the patch making the kernel cache inode data of exported directories forever, thus avoiding unnecessary disk spin-ups when this data is looked for. It looks correct, works for me and both Bruce and you have been encouraging it. :) Would be great if that could go into nfs-utils.

Thanks,
Simon

Hmmm...

Quoted 2 lines

Content-Type: video/dv;
name="nfs-utils-1.0.12-cache.dif"

So it was a video/dv file was it?

Ok, I've applied it and added a big comment.

While reflecting I remembered that I like the fact that unused information eventually disappeared from the kernel (where memory cannot be pages out). This information won't any more.

But that probably isn't a big cost.

http://neil.brown.name/git?p=nfs-utils;a=commitdiff;h=b1e1c8a05afdbbc3f217ef79c31c3b8ca302f9eb

Thanks,
NeilBrown

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#2 lore raw
Quoted 1 line · Neil Brown

http://neil.brown.name/git?p=nfs-utils;a=commitdiff;h=b1e1c8a05afdbbc3f217ef79c31c3b8ca302f9eb

Nit, typo: "log" -> "long"

* change underneath us, and an 'exportfs -f' can always
* remove this from the kernel, so use a really log
* timeout. Maybe this should be configurable on the command

Tom.

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#3 lore raw
In reply to Neil Brown
Quoted 5 lines · Neil Brown

While reflecting I remembered that I like the fact that unused information eventually disappeared from the kernel (where memory cannot be pages out). This information won't any more.

But that probably isn't a big cost.

The cost of the export structure itself should be very small. I would have guessed that the it's the mounts that are the bigger problem. But I think additional work is needed to allow us to keep only currently used filesystems mounted.

And in any case if Olaf is right then it may not be the cost of keeping those filesystems mounted so much as the time required to mount them all at once on startup. So that might be the problem to work on first.

But I wonder how much memory it takes to keep a few thousand mounts? And in addition to the memory, are there any bits of VFS code that don't scale well to lots of mounts?

--b.

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