linux-kernel - Re: [PATCH v3] mm: swap: properly update readahead statistics in unuse_pte

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Message-Id: <20200416210646.774bae8c321e3a44d6ffa8c3@linux-foundation.org>
Date:   Thu, 16 Apr 2020 21:06:46 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Huang\, Ying" <ying.huang@...el.com>
Cc:     Andrea Righi <andrea.righi@...onical.com>,
        Minchan Kim <minchan@...nel.org>,
        Anchal Agarwal <anchalag@...zon.com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] mm: swap: properly update readahead statistics in
 unuse_pte_range()

On Fri, 17 Apr 2020 11:01:22 +0800 "Huang\, Ying" <ying.huang@...el.com> wrote:

> Andrea Righi <andrea.righi@...onical.com> writes:
> 
> > In unuse_pte_range() we blindly swap-in pages without checking if the
> > swap entry is already present in the swap cache.
> >
> > By doing this, the hit/miss ratio used by the swap readahead heuristic
> > is not properly updated and this leads to non-optimal performance during
> > swapoff.
> 
> It's more important to describe why we need this patch in the patch
> description.  So, please add some information about your use case.  And
> please focus on the technical part instead of the business part.

Confused.  I thought the changelog was quite good.  If "business part"
means "end user effect of the patch" then that's a very important
thing.

> Thanks!  But you don't need to do this.  You can add my Reviewed-by after
> we have finished the work on patch description.

Can you be more specific about how you want this changed?