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From: Andrew Morton <akpm@linux-foundation.org>
To: Evan Green <evgreen@chromium.org>
Cc: David Hildenbrand <david@redhat.com>,
	Michal Hocko <mhocko@suse.com>, Pavel Machek <pavel@ucw.cz>,
	linux-api@vger.kernel.org, Alex Shi <alexs@kernel.org>,
	Alistair Popple <apopple@nvidia.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	"Matthew Wilcox (Oracle)" <willy@infradead.org>,
	Miaohe Lin <linmiaohe@huawei.com>,
	Minchan Kim <minchan@kernel.org>,
	Suren Baghdasaryan <surenb@google.com>,
	Vlastimil Babka <vbabka@suse.cz>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm@kvack.org
Subject: Re: [PATCH v4] mm: Enable suspend-only swap spaces
Date: Tue, 27 Jul 2021 14:18:32 -0700	[thread overview]
Message-ID: <20210727141832.86695e7181eb10c6e8fd0191@linux-foundation.org> (raw)
In-Reply-To: <CAE=gft7567-2Lq7raJKrOpQ8UAvXTFWwPci=_GCRPET3nS=9SA@mail.gmail.com>

On Tue, 27 Jul 2021 09:31:33 -0700 Evan Green <evgreen@chromium.org> wrote:

> > Pavel just mentioned uswsusp, and I wonder if it would be a possible
> > alternative to this patch.
> 
> I think you're right that it would be possible to isolate the
> hibernate image with uswsusp if you avoid using the SNAPSHOT_*SWAP*
> ioctls. But I'd expect performance to suffer noticeably, since now
> every page is making a round trip out to usermode and back. I'd still
> very much use the HIBERNATE_ONLY flag if it were accepted, I think
> there's value to it.

The uswsusp option makes your patch a performance optimization rather
than a feature-add.  And we do like to see quantitative testing results
when considering a performance optimization.  Especially when the
performance optimization is a bit icky, putting special-case testing
all over the place, maintenance cost, additional testing effort, etc.

I do think that diligence demands that we quantify the difference.  Is
this a thing you can help with?


  reply	other threads:[~2021-07-27 21:18 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27  0:12 Evan Green
2021-07-27  9:48 ` David Hildenbrand
2021-07-27 12:21   ` David Hildenbrand
2021-07-27 16:31     ` Evan Green
2021-07-27 21:18       ` Andrew Morton [this message]
2021-08-03 18:00         ` Evan Green
2021-08-17 18:32           ` Pavel Machek
2021-07-30 13:15 ` Karel Zak

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