linux-kernel - Re: [PATCH] zswap: Same-filled pages handling

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Message-ID: <20171018123427.GA7271@bombadil.infradead.org>
Date:   Wed, 18 Oct 2017 05:34:28 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Srividya Desireddy <srividya.dr@...sung.com>
Cc:     "sjenning@...hat.com" <sjenning@...hat.com>,
        "ddstreet@...e.org" <ddstreet@...e.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "penberg@...nel.org" <penberg@...nel.org>,
        Dinakar Reddy Pathireddy <dinakar.p@...sung.com>,
        SHARAN ALLUR <sharan.allur@...sung.com>,
        RAJIB BASU <rajib.basu@...sung.com>,
        JUHUN KIM <juhunkim@...sung.com>,
        "srividya.desireddy@...il.com" <srividya.desireddy@...il.com>
Subject: Re: [PATCH] zswap: Same-filled pages handling

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));
}

(and you should see significantly better numbers at least on x86;
I don't know if anyone's done an arm64 version of memset_l yet).