From: Jason Gunthorpe <jgg-uk2M96/98Pc@public.gmane.org>
To: Rohit Zambre <rzambre-sXc7qaQca9o@public.gmane.org>
Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: 2x difference between multi-thread and multi-process for same number of CTXs
Date: Wed, 24 Jan 2018 10:08:30 -0700 [thread overview]
Message-ID: <20180124170830.GD16845@ziepe.ca> (raw)
In-Reply-To: <CAJ84Q-aFfcXxaJS5rApcoow6SBjfZAvt71_OKo1ORorXAOZKbw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Wed, Jan 24, 2018 at 10:22:53AM -0600, Rohit Zambre wrote:
> (1) First, is this a surprising result or is the 2x difference
> actually expected behavior?
Maybe, there are lots of locks in one process, for instance glibc's
malloc has locking - so any memory allocation anywhere in the
applications processing path will cause lock contention. The issue may
have nothing to do with RDMA.
There is also some locking inside the userspace mlx5 driver that may
contend depending on how your process has set things up.
The entire send path is in user space so there is no kernel component
here.
Jason
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next prev parent reply other threads:[~2018-01-24 17:08 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-24 16:22 2x difference between multi-thread and multi-process for same number of CTXs Rohit Zambre
[not found] ` <CAJ84Q-aFfcXxaJS5rApcoow6SBjfZAvt71_OKo1ORorXAOZKbw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-24 17:08 ` Jason Gunthorpe [this message]
[not found] ` <20180124170830.GD16845-uk2M96/98Pc@public.gmane.org>
2018-01-24 20:53 ` Rohit Zambre
[not found] ` <CAJ84Q-aMW7PXFFuODm6RN=SO342=tJ4_eSJ2TB0b8DLrxgwtGQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-24 22:00 ` Anuj Kalia
[not found] ` <CADPSxAg62gpCTdD9rqVfz+hznVpa_yHig1PRvMeHs2SWc1fvsw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-26 16:44 ` Rohit Zambre
[not found] ` <CADPSxAj1wbNUqCpwigorpoQgGMVCAJ1TiQ5CuCxvSkVWd6LThQ@mail.gmail.com>
[not found] ` <CADPSxAj1wbNUqCpwigorpoQgGMVCAJ1TiQ5CuCxvSkVWd6LThQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-26 20:14 ` Rohit Zambre
[not found] ` <CAJ84Q-avu53954aECPKBHv2RR3KeH3ra4S+duLsFQeb3pp2+ww-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-01-26 22:34 ` Anuj Kalia
[not found] ` <CADPSxAgMeCdFsnrCAKLtGZp_aJp78LMB2VUObsr3_s-p6vu-MA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2018-02-07 0:02 ` Rohit Zambre
2018-01-24 22:22 ` Jason Gunthorpe
[not found] ` <20180124222240.GA10706-uk2M96/98Pc@public.gmane.org>
2018-01-24 23:04 ` Rohit Zambre
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