Re: [PATCH] prune_icache_sb

Wendy Cheng
2006-12-04T05:50:25Z

Andrew Morton wrote:

>On Sun, 03 Dec 2006 12:49:42 -0500
>Wendy Cheng <wcheng@redhat.com> wrote:
>
>
>
>>I read this as "It is ok to give system admin(s) commands (that this
>>"drop_pagecache_sb() call" is all about) to drop page cache. It is,
>>however, not ok to give filesystem developer(s) this very same function
>>to trim their own page cache if the filesystems choose to do so" ?
>>
>>
>
>If you're referring to /proc/sys/vm/drop_pagecache then no, that isn't for
>administrators - it's a convenience thing for developers, to get repeatable
>benchmarks. Attempts to make it a per-numa-node control for admin purposes have
>been rejected.
>
>
Just saw you suggested the "next door" LKML thread ("la la la la ...
swappiness") to use "-o sync" ? Well, now I do see you're determined ...
anyway, I think I got my stuff working without this kernel patch ...
still under testing though.

The rename post will be done first thing tomorrow morning.

>>[snip] .......
>>
>>
>hmm, I suppose that makes sense.
>
>Are there dentries associated with these locks?
>
>
Yes, dentries are part of the logic (during lookup time) but
book-keepings (reference count, reclaim, delete, etc) are all done thru
inode structures.

>
>
>>>Did you look at improving that lock-lookup algorithm, btw? Core kernel has
>>>no problem maintaining millions of cached VFS objects - is there any reason
>>>why your lock lookup cannot be similarly efficient?
>>>
>>>
>>>
Yes, just found the new DLM uses "jhash" call (include/linux/jhash.h).
I'm on an older version of DLM that uses FNV hash algorithm
(http://www.isthe.com/chongo/tech/comp/fnv/). Will do some performance
test runs to compare these two methods.

A final note on this subject - I may not agree with you (about various
things) but your comments and amazingly quick responses are very very
appreciated !

-- Wendy