Varnish, long lived cache and purge on change

Poul-Henning Kamp phk at
Wed Aug 19 17:51:26 CEST 2009

In message <4A8BB076.50009 at>, Rob S writes:
>phk and other deep Varnish developers,
>Do you think it'd ever be viable to have a sort of process that goes 
>through the tail of the purge queue and applies the purges then deletes 
>them from the queue?  If so, how much work would it be to implement?  

Right now we do not know which objects hold onto a ban, only the
number of objects that do.

Do implement it, we would need to put a linked list in each ban
and wire the referencing objects onto it.

My only worry is that it adds a linked list to the objcore structure
taking it from 88 to 104 bytes.

I seem to recall that the locking is benign.

Probably the more interesting question is how aggressive you want it to
be: if it is too militant, it will cause a lot of needless disk activity.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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