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From: "Benoit Ganne (bganne)" <bganne@cisco.com>
To: "users@dpdk.org" <users@dpdk.org>
Cc: "contact@filipjaniszewski.com" <contact@filipjaniszewski.com>
Subject: Re: [dpdk-users] Bigger mempool leads to worst performances.
Date: Thu, 18 Jun 2020 10:26:25 +0000
Message-ID: <SN6PR11MB3101F76080EF0D51ACDC8AC3C19B0@SN6PR11MB3101.namprd11.prod.outlook.com> (raw)

> It looks like that in our environment increasing the mempool reduce the
> capture performance, any suggestion on what I might look at to
> troubleshoot the problem? Apparently we can't go beyond 4GiB mempool
> without performance penalties.
> (Please note that 1GiB hugepage are configured to serve all the require
> additional memory.)

I'd bet it on page walks because of TLB misses: if I am not mistaken, on Intel you only have 4 TLB entries for 1GB hugepages, and prior to Skylake you have no victim cache. So, as soon as you use more than 4 x 1GB hugepages, you'll start triggering page walks because all your pages do no longer fit in the TLB.
You should be able to check that with 'perf stat -e dTLB-loads,dTLB-load-misses,dTLB-stores,dTLB-store-misses -a -I1000' or similar.

Best
ben

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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-18 10:26 Benoit Ganne (bganne) [this message]
  -- strict thread matches above, loose matches on Subject: below --
2020-06-17 14:02 Filip Janiszewski

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