From: Jesper Dangaard Brouer <jbrouer@redhat.com>
To: Joe Damato <jdamato@fastly.com>, netdev@vger.kernel.org
Cc: brouer@redhat.com, kuba@kernel.org, davem@davemloft.net,
ilias.apalodimas@linaro.org, hawk@kernel.org,
Tariq Toukan <ttoukan.linux@gmail.com>,
Saeed Mahameed <saeed@kernel.org>
Subject: Re: [PATCH 1/6] net: page_pool: Add alloc stats and fast path stat
Date: Wed, 2 Feb 2022 15:14:34 +0100 [thread overview]
Message-ID: <1302c302-1a4b-ff0d-c989-cbe851c92e06@redhat.com> (raw)
In-Reply-To: <1643237300-44904-2-git-send-email-jdamato@fastly.com>
On 26/01/2022 23.48, Joe Damato wrote:
> @@ -86,6 +100,7 @@ struct page_pool_params {
>
> struct page_pool {
> struct page_pool_params p;
> + struct page_pool_stats ps;
>
> struct delayed_work release_dw;
The placement of page_pool_stats is problematic, due to cache-line
placement.
It will be sharing a cache-line with page_pool_params, which is
read-mostly. As I say on benchmark email, this is likely the
performance regression you saw.
I *do* know you have changed location (to percpu) in newer patch
versions, but I think it is important to point out, that we have to be
very careful about cache-line placements, and which part of 'struct
page_pool' is accessed by which part of the code RX or
DMA-TX-completion "return" code.
--Jesper
next prev parent reply other threads:[~2022-02-02 14:14 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-26 22:48 [PATCH net-next 0/6] net: page_pool: Add page_pool stat counters Joe Damato
2022-01-26 22:48 ` [PATCH 1/6] net: page_pool: Add alloc stats and fast path stat Joe Damato
2022-01-27 16:32 ` Jakub Kicinski
2022-01-27 21:11 ` Joe Damato
2022-02-02 14:14 ` Jesper Dangaard Brouer [this message]
2022-01-26 22:48 ` [PATCH net-next 2/6] net: page_pool: Add a stat for the slow alloc path Joe Damato
2022-01-26 22:48 ` [PATCH net-next 3/6] net: page_pool: Add a high order alloc stat Joe Damato
2022-01-26 22:48 ` [PATCH net-next 4/6] net: page_pool: Add stat tracking empty ring Joe Damato
2022-01-26 22:48 ` [PATCH net-next 5/6] net: page_pool: Add stat tracking cache refills Joe Damato
2022-01-26 22:48 ` [PATCH 6/6] net: page_pool: Add a stat tracking waived pages Joe Damato
2022-01-27 8:51 ` [PATCH net-next 0/6] net: page_pool: Add page_pool stat counters Jesper Dangaard Brouer
2022-01-27 21:08 ` Joe Damato
2022-02-02 14:04 ` Jesper Dangaard Brouer
2022-01-27 9:08 ` Ilias Apalodimas
2022-01-27 23:55 ` Joe Damato
2022-01-29 14:07 ` Ilias Apalodimas
2022-01-29 18:07 ` Joe Damato
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