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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Hui Zhu <zhuhui@xiaomi.com>
Cc: minchan@kernel.org, ngupta@vflare.org,
	sergey.senozhatsky.work@gmail.com, hughd@google.com,
	rostedt@goodmis.org, mingo@redhat.com, peterz@infradead.org,
	acme@kernel.org, alexander.shishkin@linux.intel.com,
	akpm@linux-foundation.org, mhocko@suse.com, hannes@cmpxchg.org,
	mgorman@techsingularity.net, vbabka@suse.cz,
	redkoi@virtuozzo.com, luto@kernel.org,
	kirill.shutemov@linux.intel.com, geliangtang@163.com,
	baiyaowei@cmss.chinamobile.com, dan.j.williams@intel.com,
	vdavydov@virtuozzo.com, aarcange@redhat.com, dvlasenk@redhat.com,
	jmarchan@redhat.com, koct9i@gmail.com, yang.shi@linaro.org,
	dave.hansen@linux.intel.com, vkuznets@redhat.com,
	vitalywool@gmail.com, ross.zwisler@linux.intel.com,
	tglx@linutronix.de, kwapulinski.piotr@gmail.com, axboe@fb.com,
	mchristi@redhat.com, joe@perches.com, namit@vmware.com,
	riel@redhat.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, teawater@gmail.com
Subject: Re: [RFC 0/4] ZRAM: make it just store the high compression rate page
Date: Thu, 25 Aug 2016 15:09:57 +0900	[thread overview]
Message-ID: <20160825060957.GA568@swordfish> (raw)
In-Reply-To: <1471854309-30414-1-git-send-email-zhuhui@xiaomi.com>

Hello,

On (08/22/16 16:25), Hui Zhu wrote:
> 
> Current ZRAM just can store all pages even if the compression rate
> of a page is really low.  So the compression rate of ZRAM is out of
> control when it is running.
> In my part, I did some test and record with ZRAM.  The compression rate
> is about 40%.
> 
> This series of patches make ZRAM can just store the page that the
> compressed size is smaller than a value.
> With these patches, I set the value to 2048 and did the same test with
> before.  The compression rate is about 20%.  The times of lowmemorykiller
> also decreased.

I haven't looked at the patches in details yet. can you educate me a bit?
is your test stable? why the number of lowmemorykill-s has decreased?
... or am reading "The times of lowmemorykiller also decreased" wrong?

suppose you have X pages that result in bad compression size (from zram
point of view). zram stores such pages uncompressed, IOW we have no memory
savings - swapped out page lands in zsmalloc PAGE_SIZE class. now you
don't try to store those pages in zsmalloc, but keep them as unevictable.
so the page still occupies PAGE_SIZE; no memory saving again. why did it
improve LMK?

	-ss

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  parent reply	other threads:[~2016-08-25  6:09 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-22  8:25 [RFC 0/4] ZRAM: make it just store the high compression rate page Hui Zhu
2016-08-22  8:25 ` [RFC 1/4] vmscan.c: shrink_page_list: unmap anon pages after pageout Hui Zhu
2016-08-22  8:25 ` [RFC 2/4] Add non-swap page flag to mark a page will not swap Hui Zhu
2016-09-06 15:35   ` Steven Rostedt
2016-08-22  8:25 ` [RFC 3/4] ZRAM: do not swap the page that compressed size bigger than non_swap Hui Zhu
2016-08-22  8:25 ` [RFC 4/4] vmscan.c: zram: add non swap support for shmem file pages Hui Zhu
2016-08-24  1:04 ` [RFC 0/4] ZRAM: make it just store the high compression rate page Minchan Kim
2016-08-24  1:29   ` Hui Zhu
2016-08-25  6:09 ` Sergey Senozhatsky [this message]
2016-08-25  8:25   ` Hui Zhu
2016-09-05  2:18     ` Minchan Kim
2016-09-05  3:59       ` Sergey Senozhatsky
2016-09-05  5:12       ` Hui Zhu
2016-09-05  5:51         ` Minchan Kim
2016-09-05  6:02           ` Hui Zhu
2016-09-05  2:12 ` Minchan Kim

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