Re: [PATCH] Bug 3150: do not start useless unlinkd.

On 10/08/2011 01:25 PM, Henrik Nordström wrote:
> fre 2011-10-07 klockan 11:50 +0400 skrev Dmitry Kurochkin:
>
>> I did not know that -N was used for anything but testing and debugging.
>> Perhaps we should also use diskers in -N mode?
>
> -N is not only a debugging flag. It's used in production in many setups
> where a usable system monitor keeps track of the process. It's "Do not
> daemonize", functionality should otherwise be the same.
>
>> (Though, neither Mac OS X nor Debian (by default) use upstart. Ubuntu
>> does.)
>
> And fedora uses systemd.
>
>> We should add mayUseUnlinkd() method to DiskIOStrategy. But only UFS
>> SwapDir would relay answer from it. Other store modules do not need
>> unlinkd even if the underlying IO strategy may use it. Do you agree?
>
> Or perhaps simply start it on first use, similar to how we runtime add
> more helpers of other types when needed?

I like the direction of that approach in general.

If we fork() to start unlinkd, then the fork() becomes the more
expensive the longer we delay it because Squid allocates more and more
memory, right? If so, waiting until the first unlink seems wrong.
However, if we already fork other helpers that way, perhaps that is OK.

[Forking during reconfigure will be the most expensive, but it is a rare
exception rather than a rule so we can ignore it.]

If late forking is a problem, perhaps folks suffering from it should
invest in a simple protocol that would allow Controller or even the
Master process to fork new kids on demand?

For now, we have a choice of starting a lot of useless unlinkd processes
(without Dmitry's patch) OR starting only what we need and not
supporting switching to unlinkd during reconfigure (with Dmitry's
patch). I think the latter is better. What do you think?

Cheers,

Alex.
Received on Sun Oct 09 2011 - 18:29:24 MDT