Re: [PATCH rdma-core 5/5] Add mmio_memcpy_x64

From: Yishai Hadas <yishaih-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>
To: Jason Gunthorpe
	<jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Yishai Hadas <yishaih-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
	Majd Dibbiny <majd-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Subject: Re: [PATCH rdma-core 5/5] Add mmio_memcpy_x64
Date: Wed, 19 Apr 2017 18:54:53 +0300	[thread overview]
Message-ID: <25ceb4ac-7f30-f725-111e-54e6db2df209@dev.mellanox.co.il> (raw)
In-Reply-To: <20170418182703.GG7181-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>

On 4/18/2017 9:27 PM, Jason Gunthorpe wrote:
>>> +	} else if (sizeof(*dst_p) == 4) {
>>> +		const __be32 *src_p = src;
>>> +
>>> +		do {
>>> +			mmio_write32_be(dst_p++, *src_p++);
>>> +			mmio_write32_be(dst_p++, *src_p++);
>>> +			bytecnt -= 2 * sizeof(*dst_p);
>>
>> Any reason not to write at least 64 bytes here before checking byte count
>> and looping again ?
>
> icache size? I debated doing that, but the consensus of the existing
> implementations seems to be against it..
>
> We could do a 32 byte unwind which is probably a similar icache
> footprint?
>
> What would you like?

I'm fine with leaving the code as is following the existing implementation.
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