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From: Boaz Harrosh <boaz@plexistor.com>
To: Matthew Wilcox <willy@infradead.org>, Oleg Nesterov <oleg@redhat.com>
Cc: Hou Tao <houtao1@huawei.com>,
	peterz@infradead.org, Ingo Molnar <mingo@redhat.com>,
	Will Deacon <will@kernel.org>, Dennis Zhou <dennis@kernel.org>,
	Tejun Heo <tj@kernel.org>, Christoph Lameter <cl@linux.com>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Jan Kara <jack@suse.cz>
Subject: Re: [RFC PATCH] locking/percpu-rwsem: use this_cpu_{inc|dec}() for read_count
Date: Thu, 17 Sep 2020 16:46:38 +0300	[thread overview]
Message-ID: <e25a3354-04e4-54e9-a45f-7305bfd1f2bb@plexistor.com> (raw)
In-Reply-To: <20200917124838.GT5449@casper.infradead.org>

On 17/09/2020 15:48, Matthew Wilcox wrote:
> On Thu, Sep 17, 2020 at 02:01:33PM +0200, Oleg Nesterov wrote:
<>
> 
> If we change bio_endio to invoke the ->bi_end_io callbacks in softirq
> context instead of hardirq context, we can change the pagecache to take
> BH-safe locks instead of IRQ-safe locks.  I believe the only reason the
> lock needs to be IRQ-safe is for the benefit of paths like:
> 

 From my totally subjective experience on the filesystem side (user of 
bio_endio) all HW block drivers I used including Nvme isci, sata... etc. 
end up calling bio_endio in softirq. The big exception to that is the 
vdX drivers under KVM. Which is very Ironic to me.
I wish we could make all drivers be uniform in this regard.

But maybe I'm just speaking crap. Its only from my limited debuging 
expirience.

Thanks
Boaz

  parent reply	other threads:[~2020-09-17 13:54 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-15 14:07 [RFC PATCH] locking/percpu-rwsem: use this_cpu_{inc|dec}() for read_count Hou Tao
2020-09-15 15:06 ` peterz
2020-09-15 15:31   ` Oleg Nesterov
2020-09-15 15:51     ` peterz
2020-09-15 16:03       ` peterz
2020-09-15 16:11         ` Will Deacon
2020-09-15 18:11           ` peterz
2020-09-16  8:20             ` Will Deacon
2020-09-15 16:47         ` Oleg Nesterov
2020-09-16 12:32         ` Hou Tao
2020-09-16 12:51           ` peterz
2020-09-17  8:48           ` Will Deacon
2020-09-24 11:55             ` Hou Tao
2020-09-29 17:49               ` Will Deacon
2020-09-29 18:07                 ` Ard Biesheuvel
2020-09-17 10:51           ` Boaz Harrosh
2020-09-17 12:01             ` Oleg Nesterov
2020-09-17 12:48               ` Matthew Wilcox
2020-09-17 13:22                 ` peterz
2020-09-17 13:34                 ` Oleg Nesterov
2020-09-17 13:46                 ` Boaz Harrosh [this message]
2020-09-17 14:46                   ` Christoph Hellwig
2020-09-18  9:07               ` Jan Kara
2020-09-18 10:01                 ` peterz
2020-09-18 10:04                   ` peterz
2020-09-18 10:07                     ` peterz
2020-09-18 10:12                   ` peterz
2020-09-18 10:48                     ` Oleg Nesterov
2020-09-18 11:03                       ` peterz
2020-09-18 13:09                         ` Oleg Nesterov
2020-09-18 13:26                           ` Jan Kara
2020-09-20 23:49                             ` Dave Chinner
2020-09-18  8:36 ` [tip: locking/urgent] locking/percpu-rwsem: Use this_cpu_{inc,dec}() " tip-bot2 for Hou Tao

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