From: Jakub Kicinski <kuba@kernel.org>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>,
netdev@vger.kernel.org, f.fainelli@gmail.com,
vivien.didelot@gmail.com, Christian Eggers <ceggers@arri.de>,
Kurt Kanzenbach <kurt@linutronix.de>
Subject: Re: [RFC PATCH 01/13] net: dsa: add plumbing for custom netdev statistics
Date: Sun, 18 Oct 2020 11:26:53 -0700 [thread overview]
Message-ID: <20201018112653.21735d08@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <20201018173649.GF456889@lunn.ch>
On Sun, 18 Oct 2020 19:36:49 +0200 Andrew Lunn wrote:
> On Sun, Oct 18, 2020 at 09:49:51AM -0700, Jakub Kicinski wrote:
> > > + struct u64_stats_sync syncp;
> > > +} __aligned(1 * sizeof(u64));
> >
> > Why aligned to u64? Compiler should pick a reasonable alignment here
> > by itself.
>
> Hi Jakub
>
> I wondered that as well. But:
>
> struct gnet_stats_basic_cpu {
> struct gnet_stats_basic_packed bstats;
> struct u64_stats_sync syncp;
> } __aligned(2 * sizeof(u64));
>
> /* often modified stats are per-CPU, other are shared (netdev->stats) */
> struct pcpu_sw_netstats {
> u64 rx_packets;
> u64 rx_bytes;
> u64 tx_packets;
> u64 tx_bytes;
> struct u64_stats_sync syncp;
> } __aligned(4 * sizeof(u64));
>
> struct pcpu_lstats {
> u64_stats_t packets;
> u64_stats_t bytes;
> struct u64_stats_sync syncp;
> } __aligned(2 * sizeof(u64));
>
> Cargo cult or is there a real need?
Hm, looks like the intent is to enforce power of two alignment
to prevent the structure from spanning cache lines. Doesn't make
any difference for 1 counter, but I guess we can keep the style
for consistency.
next prev parent reply other threads:[~2020-10-18 18:26 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-17 21:35 [RFC PATCH 00/13] Generic TX reallocation for DSA Vladimir Oltean
2020-10-17 21:35 ` [RFC PATCH 01/13] net: dsa: add plumbing for custom netdev statistics Vladimir Oltean
2020-10-17 22:13 ` Florian Fainelli
2020-10-17 23:15 ` Andrew Lunn
2020-10-18 0:23 ` Vladimir Oltean
2020-10-18 12:02 ` Heiner Kallweit
2020-10-18 12:16 ` Vladimir Oltean
2020-10-18 13:09 ` Heiner Kallweit
2020-10-18 13:48 ` Vladimir Oltean
2020-10-18 14:13 ` Heiner Kallweit
2020-10-18 22:58 ` Vladimir Oltean
2020-10-18 23:11 ` Florian Fainelli
2020-10-19 0:21 ` Vladimir Oltean
2020-10-19 3:49 ` Florian Fainelli
2020-10-19 12:05 ` Andrew Lunn
2020-10-19 16:27 ` Florian Fainelli
2020-10-18 16:49 ` Jakub Kicinski
2020-10-18 17:36 ` Andrew Lunn
2020-10-18 18:26 ` Jakub Kicinski [this message]
2020-10-18 18:33 ` Jakub Kicinski
2020-10-17 21:36 ` [RFC PATCH 02/13] net: dsa: implement a central TX reallocation procedure Vladimir Oltean
2020-10-17 22:01 ` Vladimir Oltean
2020-10-17 22:11 ` Florian Fainelli
2020-10-17 22:17 ` Vladimir Oltean
2020-10-18 0:37 ` Florian Fainelli
2020-10-19 8:33 ` David Laight
2020-10-19 10:30 ` Vladimir Oltean
2020-10-19 11:14 ` David Laight
2020-10-19 11:41 ` Vladimir Oltean
2020-10-19 12:19 ` Andrew Lunn
2020-10-17 22:31 ` Vladimir Oltean
2020-10-18 0:13 ` Vladimir Oltean
2020-10-18 10:36 ` Christian Eggers
2020-10-18 11:42 ` Vladimir Oltean
2020-10-18 11:59 ` Christian Eggers
2020-10-18 12:15 ` Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 03/13] net: dsa: tag_ksz: don't allocate additional memory for padding/tagging Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 04/13] net: dsa: trailer: " Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 05/13] net: dsa: tag_qca: let DSA core deal with TX reallocation Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 06/13] net: dsa: tag_ocelot: " Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 07/13] net: dsa: tag_mtk: " Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 08/13] net: dsa: tag_lan9303: " Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 09/13] net: dsa: tag_edsa: " Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 10/13] net: dsa: tag_brcm: " Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 11/13] net: dsa: tag_dsa: " Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 12/13] net: dsa: tag_gswip: " Vladimir Oltean
2020-10-17 22:19 ` Vladimir Oltean
2020-10-17 21:36 ` [RFC PATCH 13/13] net: dsa: tag_ar9331: " Vladimir Oltean
2020-10-17 23:07 ` [RFC PATCH 00/13] Generic TX reallocation for DSA Andrew Lunn
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