From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Matthew Wilcox <willy@infradead.org>, Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
sergey.senozhatsky@gmail.com, iamjoonsoo.kim@lge.com,
ngupta@vflare.org, zhouxianrong@huawei.com, zhouxiyu@huawei.com,
weidu.du@huawei.com, zhangshiming5@huawei.com,
Mi.Sophia.Wang@huawei.com, won.ho.park@huawei.com
Subject: Re: memfill
Date: Tue, 07 Feb 2017 11:07:34 -0800 [thread overview]
Message-ID: <1486494454.2488.60.camel@HansenPartnership.com> (raw)
In-Reply-To: <20170206144902.GH2267@bombadil.infradead.org>
On Mon, 2017-02-06 at 06:49 -0800, 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)
If we're going to do this, are you sure we wouldn't be wanting a string
fill instead of a memfill (because filling either by byte or long looks
a bit restrictive) assuming static strings that we can tell the compile
time size of, it would be easy for generic code to optimise.
James
next prev parent reply other threads:[~2017-02-07 19:08 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-05 15:16 [PATCH v4] zram: extend zero pages to same element pages Minchan Kim
2017-02-06 14:49 ` memfill Matthew Wilcox
2017-02-07 2:47 ` memfill zhouxianrong
2017-02-07 4:59 ` memfill Minchan Kim
2017-02-07 19:07 ` James Bottomley [this message]
2017-02-08 18:04 ` memfill Matthew Wilcox
2017-02-08 21:01 ` memfill James Bottomley
2017-02-08 21:54 ` memfill Matthew Wilcox
2017-02-07 6:57 ` [PATCH v4] zram: extend zero pages to same element pages Minchan Kim
2017-02-07 9:40 ` memfill David Howells
2017-02-07 17:22 ` memfill Matthew Wilcox
2017-02-07 17:29 ` memfill David Howells
2017-02-07 19:03 ` memfill Matthew Wilcox
2017-03-11 14:56 ` memfill v2 now with ARM and x86 implementations Matthew Wilcox
2017-03-13 5:17 ` Minchan Kim
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