On Wed, Sep 04, 2002 at 02:33:41PM +0200, Martin Wilck wrote:
> Hi,
>
> I posted a patch to netfilter-devel a week ago that fixes a severe
> performance problem with ip_conntrack_hash() (see below).
> Harald rejected it (sort of), telling me I should have read past threads
> about the hash function first.
no, I didn't reject it. I just said you should contribute your work
with the work of the other people, so we end up having one
conntrack-optimization patch.
> Although it certainly isn't the "optimal" hash function for
> ip_conntrack, it fixes a problem that leads to extremely unbalanced
> hashing in some situations, in particular in a simple
> client<->router<->webserver scenario.
It is an artificial case, in which you have a single client opening
thousands of connections to a single port on a singles server. Please
correct me, if I misunderstood.
> This happens if the hash size is a power of 2, which is the default on
> most newer machines.
yes, this is the thing we should change right now. All other
optimizations should be sorted out as a whole.
> The fix is rather trivial (mainly the port numbers are accounted for
> outside the ntohl() function), and therefore I'd like to ask again that
> it be applied.
Would you be satisfied with making the default hashsize no longer a
power of two?
> Unless I am mistaken, the past discussions were mainly concerned with
> fine-tuning of the hash function, which is a topic my patch doesn't
> address, and can easily be done on top of it.
no, exactly the 'power-of-two' has been discussed as well.
> Regards,
> Martin
-- Live long and prosper - Harald Welte / laforge@gnumonks.org http://www.gnumonks.org/ ============================================================================ GCS/E/IT d- s-: a-- C+++ UL++++$ P+++ L++++$ E--- W- N++ o? K- w--- O- M- V-- PS+ PE-- Y+ PGP++ t++ 5-- !X !R tv-- b+++ DI? !D G+ e* h+ r% y+(*) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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