From: "Huang\, Ying" <ying.huang@intel.com>
To: Minchan Kim <minchan@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team <kernel-team@lge.com>,
Ilya Dryomov <idryomov@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [PATCH 4/5] mm:swap: respect page_cluster for readahead
Date: Tue, 12 Sep 2017 16:32:43 +0800 [thread overview]
Message-ID: <87ingonwpg.fsf@yhuang-dev.intel.com> (raw)
In-Reply-To: <20170912082253.GA2875@bbox> (Minchan Kim's message of "Tue, 12 Sep 2017 17:22:53 +0900")
Minchan Kim <minchan@kernel.org> writes:
> On Tue, Sep 12, 2017 at 04:07:01PM +0800, Huang, Ying wrote:
> < snip >
>> >> > My concern is users have been disabled swap readahead by page-cluster would
>> >> > be regressed. Please take care of them.
>> >>
>> >> How about disable VMA based swap readahead if zram used as swap? Like
>> >> we have done for hard disk?
>> >
>> > It could be with SWP_SYNCHRONOUS_IO flag which indicates super-fast,
>> > no seek cost swap devices if this patchset is merged so VM automatically
>> > disables readahead. It is in my TODO but it's orthogonal work.
>> >
>> > The problem I raised is "Why shouldn't we obey user's decision?",
>> > not zram sepcific issue.
>> >
>> > A user has used SSD as swap devices decided to disable swap readahead
>> > by some reason(e.g., small memory system). Anyway, it has worked
>> > via page-cluster for a several years but with vma-based swap devices,
>> > it doesn't work any more.
>>
>> Can they add one more line to their configuration scripts?
>>
>> echo 0 > /sys/kernel/mm/swap/vma_ra_max_order
>
> We call it as "regression", don't we?
I think this always happen when we switch default algorithm. For
example, if we had switched default IO scheduler, then the user scripts
to configure the parameters of old default IO scheduler will fail.
Best Regards,
Huang, Ying
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next prev parent reply other threads:[~2017-09-12 8:32 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-12 2:37 [PATCH 1/5] zram: set BDI_CAP_STABLE_WRITES once Minchan Kim
2017-09-12 2:37 ` [PATCH 2/5] bdi: introduce BDI_CAP_SYNCHRONOUS_IO Minchan Kim
2017-09-12 2:37 ` [PATCH 3/5] mm:swap: introduce SWP_SYNCHRONOUS_IO Minchan Kim
2017-09-12 4:48 ` Sergey Senozhatsky
2017-09-12 2:37 ` [PATCH 4/5] mm:swap: respect page_cluster for readahead Minchan Kim
2017-09-12 5:23 ` Huang, Ying
2017-09-12 6:25 ` Minchan Kim
2017-09-12 6:44 ` Huang, Ying
2017-09-12 6:52 ` Minchan Kim
2017-09-12 7:29 ` Huang, Ying
2017-09-12 7:56 ` Minchan Kim
2017-09-12 8:07 ` Huang, Ying
2017-09-12 8:22 ` Minchan Kim
2017-09-12 8:32 ` Huang, Ying [this message]
2017-09-12 23:34 ` Minchan Kim
2017-09-13 0:55 ` Huang, Ying
2017-09-12 2:37 ` [PATCH 5/5] mm:swap: skip swapcache for swapin of synchronous device Minchan Kim
2017-09-12 6:04 ` Sergey Senozhatsky
2017-09-12 6:31 ` Minchan Kim
2017-09-12 20:22 ` kbuild test robot
2017-09-13 0:16 ` Minchan Kim
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