Re: Bug with shared memory.

[Andrea Arcangeli]

On Mon, May 20, 2002 at 04:24:37PM -0300, Rik van Riel wrote:
> On Mon, 20 May 2002, Andrea Arcangeli wrote:
> 
> > With memclass_related_bhs() we automatically maximixed the amount of ram
> > available as inodes/indirects and everything else ZONE_NORMAL, after
> 
> OK, a question and a remark:
> 
> 1) does memclass_related_bhs() work if the bufferheads are
>    on another node ?  (NUMA-Q)

yes of course. With all the numa fixes all the classzone logic is
indipendent from the pgdat layer, not only during the
memclass_related_bhs check. The faster way to understand how the logic
works is to read the zone_idx/memclass define in mmzone.h.

> 2) memclass_related_bhs() will definately not work if the
>    data structure is pinned indirectly, say struct address_space
>    which is pinned by mere the existance of the page cache page
>    and cannot easily be freed

memclass_related_bhs is just for the bhs, it has nothing to do with the
address space. It's in the page->buffer side of the page, not the
page->mapping, so I don't understand very well.

the inode problem is a separate thing, nothing to do with
memclass_related_bhs(), the fix will be local to prune_icache.

For the memclass_related_bhs() fix in -aa, that's in the testing TODO
list of Martin (on the multi giga machines), he also nicely proposed to
compare it to the other throw-away-all-bh-regardless patch from Andrew
(that I actually didn't seen floating around yet but it's clear how it
works, it's a subset of memclass_related_bhs). However the right way to
test the memclass_related_bhs vs throw-away-all-bh, is to run a rewrite
test that fits in cache, so write,fsync,write,fsync,write,fsync. specweb
or any other read-only test will obviously perform exactly the same both
ways (actually theoretically a bit cpu-faster in throw-away-all-bh
because it doesn't check the bh list).

> > > or three, so he may not see your words.
> >
> > Ok. We CC'ed Rik so I assume it won't get lost in the mail flood.
> 
> I'm on holidays, don't expect patches soon :)

you shouldn't read emails either then, you know it is strictly forbidden
to read emails during vacations :). I'm kidding of course, thanks for
the fast reply!

Andrea