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: Wed, 13 Sep 2017 08:55:28 +0800 [thread overview]
Message-ID: <87efrbo1rz.fsf@yhuang-dev.intel.com> (raw)
In-Reply-To: <20170912233434.GA3686@bbox> (Minchan Kim's message of "Wed, 13 Sep 2017 08:34:34 +0900")
Minchan Kim <minchan@kernel.org> writes:
> On Tue, Sep 12, 2017 at 04:32:43PM +0800, Huang, Ying wrote:
>> 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.
>
> I don't follow what you are saying with specific example.
> If kernel did it which breaks something on userspace which has worked well,
> it should be fixed. No doubt.
>
> Even although it happened by mistakes, it couldn't be a excuse to break
> new thing, either.
>
> Simple. Fix the regression.
>
> If you insist on "swap users should fix it by themselves via modification
> of their script or it's not a regression", I don't want to waste my time to
> persuade you any more. I will ask reverting your patches to Andrew.
There is no functionality regression definitely. It may cause some
performance regression for some users, which could be resolved via some
scripts changing. Please don't mix them.
Best Regards,
Huang, Ying
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-09-13 0:55 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
2017-09-12 23:34 ` Minchan Kim
2017-09-13 0:55 ` Huang, Ying [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87efrbo1rz.fsf@yhuang-dev.intel.com \
--to=ying.huang@intel.com \
--cc=akpm@linux-foundation.org \
--cc=idryomov@gmail.com \
--cc=kernel-team@lge.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=minchan@kernel.org \
--cc=sergey.senozhatsky@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).