[syslog-ng] Leaking objects in size-4096 cache in slabinfo

[Doug Warner]

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On 12/18/2009 03:03 AM, Balazs Scheidler wrote:
> I've checked the kernel source that sockets and skbuffs have their own
> slab, thus they wouldn't show up in slab-4096.
> 
> However skbuffs data portion is stored in kmalloced memory, thus they
> would could show up in slab-4096.
> 
> The question is much memory is showing in slab-4096 (by mulitplying the
> counters with 4096 to see how much is actually allocated) and whether
> they correspond with the receive queues that you see.
> 
> Also note that if this is a 32 bit machine with lots of memory (> 4GB),
> then the additional RAM is actually _reducing_ low memory size, which
> the slab is using. Can you check /proc/meminfo to see how much low
> memory you have.
> 

We're running x86_64, so all RAM should be low-mem (although we only have 2GB).

Currently it looks like we have ~326MB in Recv-Q and our size-4096 is ~479MB.

I guess the big concern here is why our recv-q is so high and what we can do
to reduce it.

These are the current global options (nothing set on the src or dest since
this syslog server only handles the tcp connections):

options {
        chain_hostnames(off);
        dns_cache(yes);
        log_fifo_size(5000);
        flush_lines(200);
        flush_timeout(1000);
        use_fqdn(yes);
        stats_freq(300);
};

Most destinations are files but we do have one program.  The box doesn't seem
to be particularly loaded otherwise.

Do these values seem like we're trying to make syslog-ng cache too much
information?  Is there other settings we should tweak to try to get the
messages through syslog-ng faster?

- -Doug


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