Date: Sat, 02 Feb 2008 11:31:31 +0200 From: Alexander Motin <mav@FreeBSD.org> To: Robert Watson <rwatson@FreeBSD.org> Cc: freebsd-hackers@freebsd.org, freebsd-performance@freebsd.org, Julian Elischer <julian@elischer.org> Subject: Re: Memory allocation performance Message-ID: <47A43873.40801@FreeBSD.org> In-Reply-To: <20080201185435.X88034@fledge.watson.org> References: <47A25412.3010301@FreeBSD.org> <47A25A0D.2080508@elischer.org> <47A2C2A2.5040109@FreeBSD.org> <20080201185435.X88034@fledge.watson.org>
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Robert Watson wrote:
> I guess the question is: where are the cycles going? Are we suffering
> excessive cache misses in managing the slabs? Are you effectively
> "cycling through" objects rather than using a smaller set that fits
> better in the cache?
In my test setup only several objects from zone usually allocated same
time, but they allocated two times per every packet.
To check UMA dependency I have made a trivial one-element cache which in
my test case allows to avoid two for four allocations per packet.
.....alloc.....
- item = uma_zalloc(ng_qzone, wait | M_ZERO);
+ mtx_lock_spin(&itemcachemtx);
+ item = itemcache;
+ itemcache = NULL;
+ mtx_unlock_spin(&itemcachemtx);
+ if (item == NULL)
+ item = uma_zalloc(ng_qzone, wait | M_ZERO);
+ else
+ bzero(item, sizeof(*item));
.....free.....
- uma_zfree(ng_qzone, item);
+ mtx_lock_spin(&itemcachemtx);
+ if (itemcache == NULL) {
+ itemcache = item;
+ item = NULL;
+ }
+ mtx_unlock_spin(&itemcachemtx);
+ if (item)
+ uma_zfree(ng_qzone, item);
...............
To be sure that test system is CPU-bound I have throttled it with sysctl
to 1044MHz. With this patch my test PPPoE-to-PPPoE router throughput has
grown from 17 to 21Mbytes/s. Profiling results I have sent promised
close results.
> Is some bit of debugging enabled that shouldn't
> be, perhaps due to a failure of ifdefs?
I have commented out all INVARIANTS and WITNESS options from GENERIC
kernel config. What else should I check?
--
Alexander Motin
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