From: Thomas Gleixner <tglx@linutronix.de>
To: Eric Dumazet <edumazet@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linuxfoundation.org>,
x86@kernel.org, Wangyang Guo <wangyang.guo@intel.com>,
Arjan van De Ven <arjan@linux.intel.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
netdev@vger.kernel.org, Will Deacon <will@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Boqun Feng <boqun.feng@gmail.com>,
Mark Rutland <mark.rutland@arm.com>,
Marc Zyngier <maz@kernel.org>
Subject: Re: [patch 1/3] net: dst: Prevent false sharing vs. dst_entry::__refcnt
Date: Tue, 28 Feb 2023 22:31:40 +0100 [thread overview]
Message-ID: <875yblmq83.ffs@tglx> (raw)
In-Reply-To: <CANn89iKM6yMP2Doy0MuCrfX1LASPFt_OnpPY-aNg+hu=F3W7AA@mail.gmail.com>
Eric!
On Tue, Feb 28 2023 at 16:17, Eric Dumazet wrote:
> On Tue, Feb 28, 2023 at 3:33 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>> perf top identified two affected read accesses. dst_entry::lwtstate and
>> rtable::rt_genid.
>>
>> dst_entry:__refcnt is located at offset 64 of dst_entry, which puts it into
>> a seperate cacheline vs. the read mostly members located at the beginning
>> of the struct.
>
> This will probably increase struct rt6_info past the 4 cache line
> size, right ?
pahole says: /* size: 256, cachelines: 4, members: 11 */
> It would be nice to allow sharing the 'hot' cache line with seldom
> used fields.
Sure.
> Instead of mere pads, add some unions, and let rt6i_uncached/rt6i_uncached_list
> use them.
If I understand correctly, you suggest to move
rt6_info::rt6i_uncached[_list], rtable::rt_uncached[_list]
into struct dst_entry and fixup the usage sites, right?
I don't see why that would need a union. dst_entry::rt_uncached[_list]
would work for both, no?
Thanks,
tglx
next prev parent reply other threads:[~2023-02-28 21:31 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-28 14:33 [patch 0/3] net, refcount: Address dst_entry reference count scalability issues Thomas Gleixner
2023-02-28 14:33 ` [patch 1/3] net: dst: Prevent false sharing vs. dst_entry::__refcnt Thomas Gleixner
2023-02-28 15:17 ` Eric Dumazet
2023-02-28 21:31 ` Thomas Gleixner [this message]
2023-03-01 23:12 ` Thomas Gleixner
2023-02-28 14:33 ` [patch 2/3] atomics: Provide rcuref - scalable reference counting Thomas Gleixner
2023-03-01 0:42 ` Linus Torvalds
2023-03-01 1:07 ` Linus Torvalds
2023-03-01 11:09 ` Thomas Gleixner
2023-03-02 1:05 ` Thomas Gleixner
2023-03-02 1:29 ` Randy Dunlap
2023-03-02 19:36 ` Linus Torvalds
2023-02-28 14:33 ` [patch 3/3] net: dst: Switch to rcuref_t " Thomas Gleixner
2023-02-28 15:07 ` [patch 0/3] net, refcount: Address dst_entry reference count scalability issues Eric Dumazet
2023-02-28 16:38 ` Thomas Gleixner
2023-02-28 16:59 ` Eric Dumazet
2023-03-01 1:00 ` Thomas Gleixner
2023-03-01 3:17 ` Jakub Kicinski
2023-03-01 10:40 ` Thomas Gleixner
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