Nice catch.
Patch applied.
Thanks for your work with that one.
Cheers,
Simon.
On 11/02/2019 16:04, Florent Fourcot wrote:
> We detected a performance issue on a dnsmasq running many dhcp sessions
> (more than 10 000). At the end of the day, the server was only releasing
> old DHCP leases but was consuming a lot of CPU.
>
> It looks like curent dhcp pruning:
> 1) it's pruning old sessions (iterate on all current leases). It's
> important to note that it's only pruning session expired since more
> than one second
> 2) it's looking for next lease to expire (iterate on all current leases
> again)
> 3) it launchs an alarm to catch next expiration found in step 2). This
> value can be zero for leases just expired (but not pruned).
>
> So, for a second, dnsmasq could fall in a "prune loop" by doing:
> * Not pruning anything, since difftime() is not > 0
> * Run alarm again with zero as argument
>
> On a server with very large number of leases and releasing often
> sessions, that can waste a very big CPU time.
>
> Signed-off-by: Florent Fourcot <florent.four...@wifirst.fr>
> ---
> src/lease.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/src/lease.c b/src/lease.c
> index 97bee21..7299227 100644
> --- a/src/lease.c
> +++ b/src/lease.c
> @@ -563,7 +563,7 @@ void lease_prune(struct dhcp_lease *target, time_t now)
> for (lease = leases, up = &leases; lease; lease = tmp)
> {
> tmp = lease->next;
> - if ((lease->expires != 0 && difftime(now, lease->expires) > 0) ||
> lease == target)
> + if ((lease->expires != 0 && difftime(now, lease->expires) >= 0) ||
> lease == target)
> {
> file_dirty = 1;
> if (lease->hostname)
>
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