From: Srividya Desireddy <srividya.dr@samsung.com>
To: Matthew Wilcox <willy@infradead.org>,
Timofey Titovets <nefelim4ag@gmail.com>
Cc: "sjenning@redhat.com" <sjenning@redhat.com>,
"ddstreet@ieee.org" <ddstreet@ieee.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"penberg@kernel.org" <penberg@kernel.org>,
Dinakar Reddy Pathireddy <dinakar.p@samsung.com>,
SHARAN ALLUR <sharan.allur@samsung.com>,
RAJIB BASU <rajib.basu@samsung.com>,
JUHUN KIM <juhunkim@samsung.com>,
"srividya.desireddy@gmail.com" <srividya.desireddy@gmail.com>
Subject: Re: [PATCH] zswap: Same-filled pages handling
Date: Wed, 18 Oct 2017 14:43:50 +0000 [thread overview]
Message-ID: <20171018144350epcms5p1f390fae66f1c9440b8552acec555ca01@epcms5p1> (raw)
In-Reply-To: <20171018141116.GA12063@bombadil.infradead.org>
On Wed, Oct 18, 2017 at 7:41 PM, Matthew Wilcox wrote:
> On Wed, Oct 18, 2017 at 04:33:43PM +0300, Timofey Titovets wrote:
>> 2017-10-18 15:34 GMT+03:00 Matthew Wilcox <willy@infradead.org>:
>> > On Wed, Oct 18, 2017 at 10:48:32AM +0000, Srividya Desireddy wrote:
>> >> +static void zswap_fill_page(void *ptr, unsigned long value)
>> >> +{
>> >> + unsigned int pos;
>> >> + unsigned long *page;
>> >> +
>> >> + page = (unsigned long *)ptr;
>> >> + if (value == 0)
>> >> + memset(page, 0, PAGE_SIZE);
>> >> + else {
>> >> + for (pos = 0; pos < PAGE_SIZE / sizeof(*page); pos++)
>> >> + page[pos] = value;
>> >> + }
>> >> +}
>> >
>> > I think you meant:
>> >
>> > static void zswap_fill_page(void *ptr, unsigned long value)
>> > {
>> > memset_l(ptr, value, PAGE_SIZE / sizeof(unsigned long));
>> > }
>>
>> IIRC kernel have special zero page, and if i understand correctly.
>> You can map all zero pages to that zero page and not touch zswap completely.
>> (Your situation look like some KSM case (i.e. KSM can handle pages
>> with same content), but i'm not sure if that applicable there)
>
>You're confused by the word "same". What Srividya meant was that the
>page is filled with a pattern, eg 0xfffefffefffefffe..., not that it is
>the same as any other page.
In kernel there is a special zero page or empty_zero_page which is in
general allocated in paging_init() function, to map all zero pages. But,
same-value-filled pages including zero pages exist in memory because
applications may be initializing the allocated pages with a value and not
using them; or the actual content written to the memory pages during
execution itself is same-value, in case of multimedia data for example.
I had earlier posted a patch with similar implementaion of KSM concept
for Zswap:
https://lkml.org/lkml/2016/8/17/171
https://lkml.org/lkml/2017/2/17/612
- Srividya
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prev parent reply other threads:[~2017-10-18 14:43 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p1>
2017-10-18 10:48 ` [PATCH] zswap: Same-filled pages handling Srividya Desireddy
2017-10-18 12:34 ` Matthew Wilcox
2017-10-18 13:33 ` Timofey Titovets
2017-10-18 14:11 ` Matthew Wilcox
2017-10-18 20:43 ` Andi Kleen
2017-10-19 1:10 ` Matthew Wilcox
2017-10-19 4:30 ` Andi Kleen
2017-10-19 13:24 ` Matthew Wilcox
2017-10-18 21:31 ` Timofey Titovets
2017-10-19 1:08 ` Matthew Wilcox
[not found] ` <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p3>
2017-11-02 15:08 ` Srividya Desireddy
2017-11-17 22:10 ` Dan Streetman
2017-11-17 22:07 ` Dan Streetman
2017-11-17 21:27 ` Dan Streetman
2017-11-20 23:46 ` Andrew Morton
2017-11-28 11:35 ` Dan Streetman
[not found] ` <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p6>
2017-11-29 15:34 ` [PATCH] zswap: Update with same-value filled page feature Srividya Desireddy
2017-11-29 21:29 ` Dan Streetman
2017-12-06 11:48 ` [PATCH v2] " Srividya Desireddy
2017-12-06 15:20 ` Dan Streetman
[not found] ` <CGME20171018104832epcms5p1b2232e2236258de3d03d1344dde9fce0@epcms5p4>
2017-11-21 14:18 ` [PATCH v2] zswap: Same-filled pages handling Srividya Desireddy
2017-10-18 14:43 ` Srividya Desireddy [this message]
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