netdev - Re: [PATCH v4 net-next 00/19] inet: frags: bring rhashtables to IP defrag

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Message-Id: <20180331.232558.823542518953124984.davem@davemloft.net>
Date:   Sat, 31 Mar 2018 23:25:58 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, fw@...len.de, herbert@...dor.apana.org.au,
        tgraf@...g.ch, brouer@...hat.com, alex.aring@...il.com,
        stefan@....samsung.com, ktkhai@...tuozzo.com,
        eric.dumazet@...il.com
Subject: Re: [PATCH v4 net-next 00/19] inet: frags: bring rhashtables to IP
 defrag

From: Eric Dumazet <edumazet@...gle.com>
Date: Sat, 31 Mar 2018 12:58:41 -0700

> IP defrag processing is one of the remaining problematic layer in linux.
> 
> It uses static hash tables of 1024 buckets, and up to 128 items per bucket.
> 
> A work queue is supposed to garbage collect items when host is under memory
> pressure, and doing a hash rebuild, changing seed used in hash computations.
> 
> This work queue blocks softirqs for up to 25 ms when doing a hash rebuild,
> occurring every 5 seconds if host is under fire.
> 
> Then there is the problem of sharing this hash table for all netns.
> 
> It is time to switch to rhashtables, and allocate one of them per netns
> to speedup netns dismantle, since this is a critical metric these days.
> 
> Lookup is now using RCU, and 64bit hosts can now provision whatever amount
> of memory needed to handle the expected workloads.
 ...

Series applied, thanks Eric.