Re: kernel.org mirroring (Re: [GIT PULL] MMC update)

[Linus Torvalds <torvalds@osdl.org>]

On Fri, 8 Dec 2006, Jeff Garzik wrote:
>
> This is a bit cheesy, and completely untested, but since mod_cache never
> worked for me either, I bet it works better ;-)

Ok, this doesn't do the locking either, so on cache misses or expiry, 
you're still going to be that thundering herd.

Also, if you want to be nice to clients, I'd seriously suggest that when 
you hit in the cache, but it's expired (or it's close to expired), you 
still serve the cached data back, but you set up a thread in the 
background (with some maximum number of active threads, of course!) that 
refreshes the cached entry and then you extend the expiration time so that 
you won't end up doing this "refresh" _again_.

It's kind of silly to have people wait for 20 seconds just because a cache 
expired five seconds ago. Much nicer to say "ok, we allow a certain 
grace-period during which we'll do the real lookup, but to make things 
_look_ really responsive, we still use the old cached value".