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Re: memfill

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On 2017/2/6 22:49, Matthew Wilcox wrote:
>
> [adding linux-arch to see if anyone there wants to do an optimised
> version of memfill for their CPU]
>
> On Mon, Feb 06, 2017 at 12:16:44AM +0900, Minchan Kim wrote:
>> +static inline void zram_fill_page(char *ptr, unsigned long len,
>> +					unsigned long value)
>> +{
>> +	int i;
>> +	unsigned long *page = (unsigned long *)ptr;
>> +
>> +	WARN_ON_ONCE(!IS_ALIGNED(len, sizeof(unsigned long)));
>> +
>> +	if (likely(value == 0)) {
>> +		memset(ptr, 0, len);
>> +	} else {
>> +		for (i = 0; i < len / sizeof(*page); i++)
>> +			page[i] = value;
>> +	}
>> +}
>
> I would suggest:
>
> #ifndef __HAVE_ARCH_MEMFILL
> /**
>  * memfill - Fill a region of memory with the given value
>  * @s: Pointer to the start of the region.
>  * @v: The word to fill the region with.
>  * @n: The size of the region.
>  *
>  * Differs from memset() in that it fills with an unsigned long instead of
>  * a byte.  The pointer and the size must be aligned to unsigned long.
>  */
> void memfill(unsigned long *s, unsigned long v, size_t n)
> {
> 	WARN_ON_ONCE(!IS_ALIGNED(n, sizeof(v)));
>
> 	if (likely(v == 0)) {
> 		memset(s, 0, n);
> 	} else {
> 		while (n) {
> 			*s++ = v;
> 			n -= sizeof(v);
> 		}
> 	}
> }
> EXPORT_SYMBOL(memfill);
> #endif
>
> (I would also suggest this move to lib/string.c and architectures be
> given the opportunity to provide an optimised version of memfill).
>

good idea, i hope kernel could support family functions like memfill/memset_long
in lib. but this is beyond zram scope.
>
> .
>

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[PATCH v4] zram: extend zero pages to same element pages Minchan Kim <minchan@kernel.org> - 2017-02-05 16:20 +0100
  memfill Matthew Wilcox <willy@infradead.org> - 2017-02-06 15:50 +0100
    Re: memfill zhouxianrong <zhouxianrong@huawei.com> - 2017-02-07 03:50 +0100
    Re: memfill Minchan Kim <minchan@kernel.org> - 2017-02-07 06:10 +0100
    Re: memfill David Howells <dhowells@redhat.com> - 2017-02-07 10:50 +0100
      Re: memfill Matthew Wilcox <willy@infradead.org> - 2017-02-07 18:30 +0100
        Re: memfill David Howells <dhowells@redhat.com> - 2017-02-07 18:40 +0100
          Re: memfill Matthew Wilcox <willy@infradead.org> - 2017-02-07 20:10 +0100
    Re: memfill James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-07 20:10 +0100
      Re: memfill James Bottomley <James.Bottomley@HansenPartnership.com> - 2017-02-08 22:10 +0100
        Re: memfill Matthew Wilcox <willy@infradead.org> - 2017-02-08 23:00 +0100
      Re: memfill Matthew Wilcox <willy@infradead.org> - 2017-02-08 23:10 +0100
  Re: [PATCH v4] zram: extend zero pages to same element pages Minchan Kim <minchan@kernel.org> - 2017-02-07 08:00 +0100

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