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From: Thomas Monjalon <thomas@monjalon.net>
To: "David Marchand" <david.marchand@redhat.com>,
	"Mattias Rönnblom" <mattias.ronnblom@ericsson.com>,
	"Morten Brørup" <mb@smartsharesystems.com>
Cc: dev@dpdk.org, Bruce Richardson <bruce.richardson@intel.com>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Chengwen Feng <fengchengwen@huawei.com>,
	Konstantin Ananyev <konstantin.ananyev@huawei.com>
Subject: Re: [PATCH] config: limit lcore variable maximum size to 4k
Date: Fri, 08 Nov 2024 23:13:02 +0100	[thread overview]
Message-ID: <27009651.6Emhk5qWAg@thomas> (raw)
In-Reply-To: <98CBD80474FA8B44BF855DF32C47DC35E9F8B4@smartserver.smartshare.dk>

08/11/2024 20:53, Morten Brørup:
> > From: Morten Brørup [mailto:mb@smartsharesystems.com]
> > Sent: Friday, 8 November 2024 19.35
> > 
> > > From: David Marchand [mailto:david.marchand@redhat.com]
> > > Sent: Friday, 8 November 2024 19.18
> > >
> > > OVS locks all pages to avoid page faults while processing packets.
> 
> It sounds smart, so I just took a look at how it does this. I'm not sure, but it seems like it only locks pages that are actually mapped (current and future).
> 
> > > 1M for each lcore translates to allocating 128M with default build
> > > options on x86.
> > > This resulted in OOM while running unit tests in parallel.
> 
> Is the root cause the lcore variables library itself, or the unit test using a lot of memory for testing the lcore variables?
> We don't want to fix the library if the problem is elsewhere.

The fix works for our urgent issue and we want to make a release candidate soon.


> > > At the moment, the more demanding DPDK user of lcore variable is
> > > rte_service, with a 2112 bytes object.
> > >
> > > Limit the lcore variable maximum size to 4k which looks more
> > > reasonable.
> > 
> > 4 KB is not future proof.
> > 
> > Here's an example where 16 KB is cutting it close:
> > https://inbox.dpdk.org/dev/98CBD80474FA8B44BF855DF32C47DC35E9F7D0@smart
> > server.smartshare.dk/
> > 
> > Depends on how we are going to use it. 4 KB suffices if we only want to
> > use it for "small" structures.

This is what is stated in the doc:
"Lcore variables are suitable for small objects"
"The amount of data kept in lcore variables is projected to be small"

> > Would 64 KB work as a compromise?

Let's consider based on the need.
The lcore variables are new and we don't want it to degrade the DPDK footprint,
at least not in this first version.
4 KB is a memory page on common systems,
it looks reasonnable and big enough for a "variable".

Applied, thanks.



  reply	other threads:[~2024-11-08 22:13 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-11-08 18:17 David Marchand
2024-11-08 18:35 ` Morten Brørup
2024-11-08 19:53   ` Morten Brørup
2024-11-08 22:13     ` Thomas Monjalon [this message]
2024-11-08 22:34       ` Mattias Rönnblom
2024-11-08 23:11         ` Thomas Monjalon
2024-11-11  6:31           ` Mattias Rönnblom
2024-11-08 22:49       ` Morten Brørup
2024-11-08 22:23     ` Mattias Rönnblom
2024-11-08 23:52       ` Morten Brørup
2024-11-11  7:22         ` Mattias Rönnblom
2024-11-11 16:54           ` Stephen Hemminger
2024-11-08 22:02 ` Mattias Rönnblom

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