Re: 23 second kernel compile / pagemap_lru_lock improvement

[Hugh Dickins]

On Tue, 12 Mar 2002, Martin J. Bligh wrote:
> >>>> Linus:
> >>>>
> >>>> Anyway, some obvious LRU lock improvements are clearly available: 
> >>>> activate_page_nolock() shouldn't even need to take the lru lock if the 
> >>>> page is already active. 
> 
> Your suggestion seems to improve the pagemap_lru_lock contention a little:
> (make bzImage , 16 way NUMA-Q, 5 runs each)

I'm surprised it made any difference at all, I think the patch mainly
adds more tests: activate_page is only called from mark_page_accessed
(after testing !PageActive) and from fail_writepage (where usually
!PageActive).  I don't think many !PageLRU pages can get there.
Or is activate_page being called from other places in your tree?

Hugh