From: Christoph Lameter <cl@linux.com>
To: "Luis R. Rodriguez" <mcgrof@suse.com>
Cc: Borislav Petkov <bp@suse.de>, Kyle McMartin <kyle@kernel.org>,
Alok N Kataria <alokk@calsoftinc.com>,
Shobhit Dayal <shobhit@calsoftinc.com>,
Shai Fultheim <shai@scalex86.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Luis R. Rodriguez" <mcgrof@do-not-panic.com>,
mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com,
plagnioj@jcrosoft.com, tomi.valkeinen@ti.com,
daniel.vetter@intel.com, airlied@linux.ie, dledford@redhat.com,
awalls@md.metrocast.net, syrjala@sci.fi, luto@amacapital.net,
mst@redhat.com, cocci@systeme.lip6.fr,
linux-kernel@vger.kernel.org, Juergen Gross <jgross@suse.com>,
Daniel Vetter <daniel.vetter@ffwll.ch>,
Dave Airlie <airlied@redhat.com>,
Bjorn Helgaas <bhelgaas@google.com>,
x86@kernel.org
Subject: Re: [PATCH v4 2/8] init.h: add __read_mostly to early_param_on_off()
Date: Thu, 30 Apr 2015 13:46:22 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.11.1504301343190.28879@gentwo.org> (raw)
In-Reply-To: <20150430183200.GW5622@wotan.suse.de>
On Thu, 30 Apr 2015, Luis R. Rodriguez wrote:
> > But for every param declared this way? I'm not sure we want that...
>
> I'm glad you bring this up, Christoph can you or anyone else can you provide
> advise since you added __read_mostly ?
Well it should be reseved for data that is actually used frequently in hot
paths. Initially we only moved variables into __read_mostly after we saw
in performance traces that there was contention on an item because a
neighboring variable was frequently written to.
You want the __read_mostly data to be tighly packed. In the best case
multiple frequently read variables for a hot path will be next to each
other in order to reduce the number of cachelines needed to execute a
critical path. That means being selective and aware of which variables
actually benefit.
next prev parent reply other threads:[~2015-04-30 18:46 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-29 21:44 [PATCH v4 0/8] x86: address drivers that do not work with PAT Luis R. Rodriguez
2015-04-29 21:44 ` [PATCH v4 1/8] x86/mm/pat: use pr_info() and friends Luis R. Rodriguez
2015-04-30 13:56 ` Borislav Petkov
2015-04-30 18:15 ` Luis R. Rodriguez
2015-04-29 21:44 ` [PATCH v4 2/8] init.h: add __read_mostly to early_param_on_off() Luis R. Rodriguez
2015-04-30 16:00 ` Borislav Petkov
2015-04-30 18:32 ` Luis R. Rodriguez
2015-04-30 18:34 ` Luis R. Rodriguez
2015-04-30 18:42 ` Borislav Petkov
2015-04-30 18:46 ` Christoph Lameter [this message]
2015-04-29 21:44 ` [PATCH v4 3/8] init.h: add early_param_on() and early_param_off() Luis R. Rodriguez
2015-04-29 21:44 ` [PATCH v4 4/8] x86/mm/pat: use early_param_off() and redefine pat_enabled() Luis R. Rodriguez
2015-04-29 21:44 ` [PATCH v4 5/8] arch/x86/mm/pat: export pat_enabled() Luis R. Rodriguez
2015-04-29 21:44 ` [PATCH v4 6/8] ivtv: use arch_phys_wc_add() and require PAT disabled Luis R. Rodriguez
2015-04-29 21:44 ` [PATCH v4 7/8] IB/ipath: add counting for MTRR Luis R. Rodriguez
2015-04-29 21:44 ` [PATCH v4 8/8] IB/ipath: use arch_phys_wc_add() and require PAT disabled Luis R. Rodriguez
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