linux-kernel - Re: [PATCH 0/2] mm,swap: skip swap readahead for instant IO (like zswap)

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Message-Id: <20200922101250.527d9e676fefbb4c8d0cd5b9@linux-foundation.org>
Date:   Tue, 22 Sep 2020 10:12:50 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Rik van Riel <riel@...riel.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kernel-team@...com, niketa@...com, sjenning@...hat.com,
        ddstreet@...e.org, konrad.wilk@...cle.com, hannes@...xchg.org
Subject: Re: [PATCH 0/2] mm,swap: skip swap readahead for instant IO (like
 zswap)

On Mon, 21 Sep 2020 22:01:46 -0400 Rik van Riel <riel@...riel.com> wrote:

> Both with frontswap/zswap, and with some extremely fast IO devices,
> swap IO will be done before the "asynchronous" swap_readpage() call
> has returned.
> 
> In that case, doing swap readahead only wastes memory, increases
> latency, and increases the chances of needing to evict something more
> useful from memory. In that case, just skip swap readahead.

Any quantitative testing results?