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Date:   Thu, 10 Mar 2022 11:16:41 -0500
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Christoph Hellwig <hch@infradead.org>
Cc:     cgel.zte@gmail.com, axboe@kernel.dk, viro@zeniv.linux.org.uk,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, akpm@linux-foundation.org,
        Yang Yang <yang.yang29@zte.com.cn>,
        Ran Xiaokai <ran.xiaokai@zte.com.cn>
Subject: Re: [PATCH] block/psi: remove PSI annotations from submit_bio
Message-ID: <YiokaQLWeulWpiCx@cmpxchg.org>
References: <20220309094323.2082884-1-yang.yang29@zte.com.cn>
 <Yij9eygSYy5MSIA0@cmpxchg.org>
 <Yime3HdbEqFgRVtO@infradead.org>
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On Wed, Mar 09, 2022 at 10:46:52PM -0800, Christoph Hellwig wrote:
> On Wed, Mar 09, 2022 at 02:18:19PM -0500, Johannes Weiner wrote:
> > On Wed, Mar 09, 2022 at 09:43:24AM +0000, cgel.zte@gmail.com wrote:
> > > From: Yang Yang <yang.yang29@zte.com.cn>
> > > 
> > > psi tracks the time spent submitting the IO of refaulting pages[1].
> > > But after we tracks refault stalls from swap_readpage[2][3], there
> > > is no need to do so anymore. Since swap_readpage already includes
> > > IO submitting time.
> > > 
> > > [1] commit b8e24a9300b0 ("block: annotate refault stalls from IO submission")
> > > [2] commit 937790699be9 ("mm/page_io.c: annotate refault stalls from swap_readpage")
> > > [3] commit 2b413a1a728f ("mm: page_io: fix psi memory pressure error on cold swapins")
> > > 
> > > Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
> > > Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
> > 
> > It's still needed by file cache refaults!
> 
> Can we get proper annotations for those please?  These bio-level hooks are
> horrible and a maintainance nightmware.

The first version did that, but it was sprawling and not well-received:

https://lkml.org/lkml/2019/7/22/1261