Re: [Lse-tech] Minutes from 11/30 Call

[Andi K. <ak...@su...>]

> There are a number of single use rw locks
> in the kernel. Take a lot of space to allocate them all
> in the rw table,  eventually run out of space because
> we don't know when to free the info.

Growing rwlock would increase the size of struct page and
some other hash tables that probably shouldn't have per bucket locks
but have right now.

Especially growing struct page is definitely a bad idea.

> Ray- I was really hoping to find out- do people care
> about rw locks?

I care about them at least.

> 1) keep track only of the write side contention level.
> 	The problem with this is if the read is heavily the 
> 	write time could be low and you wouldnt see the contention.
> 	This is similar to what we did in Dynix/PTX, has low overhead.
> 
> 2) use a counter to keep track of fraction that somebody holds
> 	lock for read.

I (as an occasional lockstat user) would prefer (2).


-Andi