From: "tj@kernel.org" <tj@kernel.org>
To: "Boy Wu (吳勃誼)" <Boy.Wu@mediatek.com>
Cc: "boris@bur.io" <boris@bur.io>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
"linux-mediatek@lists.infradead.org"
<linux-mediatek@lists.infradead.org>,
"axboe@kernel.dk" <axboe@kernel.dk>,
"Iverlin Wang (王苳霖)" <Iverlin.Wang@mediatek.com>,
"josef@toxicpanda.com" <josef@toxicpanda.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"matthias.bgg@gmail.com" <matthias.bgg@gmail.com>,
"angelogioacchino.delregno@collabora.com"
<angelogioacchino.delregno@collabora.com>
Subject: Re: [PATCH v2] blk-cgroup: Replace u64_sync with blkg_stat_lock for stats update
Date: Thu, 11 Jul 2024 11:02:55 -1000 [thread overview]
Message-ID: <ZpBIfwThiVwstlXL@slm.duckdns.org> (raw)
In-Reply-To: <6114fbad7bce9b15806bb9fee25a1075ecb53dd1.camel@mediatek.com>
Hello,
On Thu, Jul 11, 2024 at 02:25:29AM +0000, Boy Wu (吳勃誼) wrote:
...
> I can remove the 32bit only define, but I think we need to add back the
> u64 sync, because the spin lock and the u64 sync serve different
> purposes. The spin lock is for handling concurrent problems from
> different CPUs updating stats, and u64 sync is for updating 64 bits
> data and fetching 64 bits data from different CPUs in 32bit SMP
> systems.
Hmm... so what I'm suggesting is using u64_sync for the per-cpu stat
structure as they are guaranteed to have only one updater with irq disabled
and use a spinlock for the shared iostat which can have multiple updaters
and isn't accessed that frequently.
Thanks.
--
tejun
next prev parent reply other threads:[~2024-07-11 21:02 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-10 6:13 [PATCH v2] blk-cgroup: Replace u64_sync with blkg_stat_lock for stats update boy.wu
2024-07-10 22:12 ` Tejun Heo
2024-07-11 2:25 ` Boy Wu (吳勃誼)
2024-07-11 21:02 ` tj [this message]
2024-07-12 1:39 ` Boy Wu (吳勃誼)
2024-07-12 18:38 ` tj
2024-07-15 7:15 ` Boy Wu (吳勃誼)
2024-07-15 17:21 ` tj
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