From: Konstantin Ananyev <konstantin.ananyev@huawei.com>
To: "Honnappa Nagarahalli" <Honnappa.Nagarahalli@arm.com>,
"Morten Brørup" <mb@smartsharesystems.com>,
"dev@dpdk.org" <dev@dpdk.org>
Cc: "konstantin.v.ananyev@yandex.ru" <konstantin.v.ananyev@yandex.ru>,
Wathsala Wathawana Vithanage <wathsala.vithanage@arm.com>,
nd <nd@arm.com>, nd <nd@arm.com>
Subject: RE: Ring library optimization idea
Date: Mon, 21 Aug 2023 10:19:11 +0000 [thread overview]
Message-ID: <9bb4e5524ca94cc59f652db50ae4d1ee@huawei.com> (raw)
In-Reply-To: <DBAPR08MB58146FFCA80BF6CC0869A72D981EA@DBAPR08MB5814.eurprd08.prod.outlook.com>
Hi Morten,
> > Most of the fast path ring library functions access the two cache lines containing
> > respectively the r->prod and r->cons structures.
> >
> > Some of the fast path functions also have to fetch r->capacity and r->mask,
> > which reside in another cache line.
> >
> > What do you think about adding shadow variables of r->capacity and r->mask
> > to the same cache line as r->prod, to improve ring library performance (by
> > avoiding having to read a third cache line) when under CPU cache pressure?
> Agree with the idea. I am not sure about the performance as these are read-only data. IMO, we should not worry about it as it saves
> one cache line (but we do not need to measure the performance). They will occupy 12B, but I do not see how we will occupy the
> entire 64B of the cacheline in the near future.
>
> Also, the shadow variables need to be part of both r->prod and r->cons.
Personally, I think that for majority of cases the perf gain with be either tiny or none.
From other side, I don't see any harm with that approach, as Honnapa said, we
do should have space for that in prod/cons cache-lines.
So, no objections from me in general.
Thanks
Konstantin
prev parent reply other threads:[~2023-08-21 10:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-20 9:23 Morten Brørup
2023-08-21 4:40 ` Honnappa Nagarahalli
2023-08-21 10:19 ` Konstantin Ananyev [this message]
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