lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 29 Nov 2017 16:29:42 -0500
From:   Dan Streetman <ddstreet@...e.org>
To:     Srividya Desireddy <srividya.dr@...sung.com>
Cc:     "sjenning@...hat.com" <sjenning@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dinakar Reddy Pathireddy <dinakar.p@...sung.com>,
        RAJIB BASU <rajib.basu@...sung.com>,
        Srikanth Mandalapu <srikanth.m@...sung.com>,
        SHARAN ALLUR <sharan.allur@...sung.com>,
        JUHUN KIM <juhunkim@...sung.com>,
        "srividya.desireddy@...il.com" <srividya.desireddy@...il.com>
Subject: Re: [PATCH] zswap: Update with same-value filled page feature

On Wed, Nov 29, 2017 at 10:34 AM, Srividya Desireddy
<srividya.dr@...sung.com> wrote:
> From: Srividya Desireddy <srividya.dr@...sung.com>
> Date: Wed, 29 Nov 2017 20:23:15 +0530
> Subject: [PATCH] zswap: Update with same-value filled page feature
>
> Updated zswap document with details on same-value filled
> pages identification feature.
> The usage of zswap.same_filled_pages_enabled module parameter
> is explained.
>
> Signed-off-by: Srividya Desireddy <srividya.dr@...sung.com>
> ---
>  Documentation/vm/zswap.txt | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/vm/zswap.txt b/Documentation/vm/zswap.txt
> index 89fff7d..cc015b5 100644
> --- a/Documentation/vm/zswap.txt
> +++ b/Documentation/vm/zswap.txt
> @@ -98,5 +98,25 @@ request is made for a page in an old zpool, it is uncompressed using its
>  original compressor.  Once all pages are removed from an old zpool, the zpool
>  and its compressor are freed.
>
> +Some of the pages in zswap are same-value filled pages (i.e. contents of the
> +page have same value or repetitive pattern). These pages include zero-filled
> +pages and they are handled differently. During store operation, a page is
> +checked if it is a same-value filled page before compressing it. If true, the
> +compressed length of the page is set to zero and the pattern or same-filled
> +value is stored.
> +
> +Same-value filled pages identification feature is enabled by default and can be
> +disabled at boot time by setting the "same_filled_pages_enabled" attribute to 0,
> +e.g. zswap.same_filled_pages_enabled=0. It can also be enabled and disabled at
> +runtime using the sysfs "same_filled_pages_enabled" attribute, e.g.
> +
> +echo 1 > /sys/module/zswap/parameters/same_filled_pages_enabled
> +
> +When zswap same-filled page identification is disabled at runtime, it will stop
> +checking for the same-value filled pages during store operation. However, the
> +existing pages which are marked as same-value filled pages will be loaded or
> +invalidated.

On first read I thought you were saying existing pages were
immediately loaded or invalidated, which of course is not the case.
Can you update the sentence to clarify existing pages are not modified
by disabling the param, like:

"However, the existing pages which are marked as same-value filled
pages remain stored unchanged until they are either loaded or
invalidated."

except for that the doc update looks good.

> +
>  A debugfs interface is provided for various statistic about pool size, number
> -of pages stored, and various counters for the reasons pages are rejected.
> +of pages stored, same-value filled pages and various counters for the reasons
> +pages are rejected.
> --
> 2.7.4
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@...ck.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>

Powered by blists - more mailing lists