Re: Squid sometimes doesn't use unlinkd

According to Duane Wessels:
> Miquel van Smoorenburg writes:
> >I've asked this before but got no replies, but I can't imagine I'm the
> >only one seeing this. Every once in a while our squid server (1.1.20 novm)
> >decides not to use unlinkd and does the unlinking itself.
>
> It could happen if your disk usage is over the high water mark.
> Then storeGetSwapSpace gets called:
>
> 1459 if ((i = storeGetUnusedFileno()) >= 0) {
> 1460 safeunlink(storeSwapFullPath(i, NULL), 0);
> 1461 if (++removed == SWAP_LRU_REMOVE_COUNT)
> 1462 return;
> 1463 }
>
> Don't ask me why thats there. I'm not sure I wrote it. Looks like
> the 'if' should maybe be a 'while'.

Aha, very good guess. Indeed the disk usage is over the high water mark.

> 1570 if (store_swap_size > store_swap_high)
> 1571 safeunlink(storeSwapFullPath(e->swap_file_number, NULL), 1);
> 1572 else
> 1573 storePutUnusedFileno(e->swap_file_number);
>
> Requests are only written to the unlinkd process if the unused
> fileno stack is full. If you're over the high water mark and the
> stack is NOT full, then no disk space will be freed, so we call
> unlink directly.

I'm not quite sure I understand this. There is no conceptual difference
between calling unlink() directly and calling unlinkd; why not use unlinkd?
Our cache now gets so slow sometimes that it is unuseable. All the
unlink()s take way too much time..

Ofcourse I do not understand the internals of squid very much so maybe
I'm asking for the obvious.

Mike.

-- 
 Miquel van Smoorenburg |  The dyslexic, agnostic, insomniac lay in his bed
    miquels@cistron.nl  |  awake all night wondering if there is a doG