From: David Vrabel <david.vrabel@citrix.com>
To: Felipe Franciosi <felipe@paradoxo.org>
Cc: Jens Axboe <axboe@kernel.dk>, <linux-kernel@vger.kernel.org>,
Sam Bradshaw <sbradshaw@micron.com>
Subject: Re: [PATCH 1/2] mtip32xx: Don't bounce IO requests
Date: Wed, 12 Mar 2014 17:18:32 +0000 [thread overview]
Message-ID: <532096E8.1010706@citrix.com> (raw)
In-Reply-To: <CANxchRSOpr63_GuktU_Y53y=vE0n+x6tqQ+=+uo_WgMGP13yRQ@mail.gmail.com>
On 12/03/14 17:08, Felipe Franciosi wrote:
> On Wed, Mar 12, 2014 at 4:16 PM, Jens Axboe <axboe@kernel.dk> wrote:
>>
>> On 03/12/2014 10:05 AM, Felipe Franciosi wrote:
>>>
>>> This device support 64-bit DMA and therefore no IO requests needs bouncing.
>>> On 32-bit systems, blk_queue_bounce() will bounce all IO requests with high
>>> mem pages. This makes performance really really bad.
[...]
>>> --- a/drivers/block/mtip32xx/mtip32xx.c
>>> +++ b/drivers/block/mtip32xx/mtip32xx.c
>>> @@ -4082,8 +4082,6 @@ static void mtip_make_request(struct request_queue *queue, struct bio *bio)
>>>
>>> sg = mtip_hw_get_scatterlist(dd, &tag, unaligned);
>>> if (likely(sg != NULL)) {
>>> - blk_queue_bounce(queue, &bio);
>>> -
>>> if (unlikely((bio)->bi_vcnt > MTIP_MAX_SG)) {
>>> dev_warn(&dd->pdev->dev,
>>> "Maximum number of SGL entries exceeded\n");
>>
>>
>> That seems to be because the driver forgets to set the DMA
>> capabilities. It needs a blk_queue_bounce_limit() call when it sets up
>> the queue.
>
> Hmm... I see what you are saying. David, would you like to comment?
Yes, it should also call blk_queue_bounce_limit(..., BLK_BOUNCE_ANY) in
mtip_block_initialize() as well.
But, only one other driver calls blk_queue_bounce() so it's difficult to
see why this driver would need a call here.
David
next prev parent reply other threads:[~2014-03-12 17:18 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-12 16:05 [PATCH 0/2] mtip32xx: Fix arch-specific driver issues Felipe Franciosi
2014-03-12 16:05 ` [PATCH 1/2] mtip32xx: Don't bounce IO requests Felipe Franciosi
2014-03-12 16:16 ` Jens Axboe
2014-03-12 17:08 ` Felipe Franciosi
2014-03-12 17:18 ` David Vrabel [this message]
2014-03-12 17:19 ` Jens Axboe
2014-03-12 17:44 ` Felipe Franciosi
2014-03-12 16:05 ` [PATCH 2/2] mtip32xx: Unmap the DMA segments before completing the IO request Felipe Franciosi
2014-03-12 16:16 ` Jens Axboe
2014-03-12 19:04 ` Sam Bradshaw
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