linux-kernel - Re: [PATCH 4/7] libata: use lazy workqueues for the pio task

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Message-ID: <20090824164214.GO12579@kernel.dk>
Date:	Mon, 24 Aug 2009 18:42:14 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Jeff Garzik <jeff@...zik.org>
Cc:	linux-kernel@...r.kernel.org, benh@...nel.crashing.org,
	htejun@...il.com, bzolnier@...il.com, alan@...rguk.ukuu.org.uk,
	akpm@...ux-foundation.org
Subject: Re: [PATCH 4/7] libata: use lazy workqueues for the pio task

On Mon, Aug 24 2009, Jeff Garzik wrote:
> On 08/24/2009 03:56 AM, Jens Axboe wrote:
>> Signed-off-by: Jens Axboe<jens.axboe@...cle.com>
>> ---
>>   drivers/ata/libata-core.c |    2 +-
>>   1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
>> index 072ba5e..35f74c9 100644
>> --- a/drivers/ata/libata-core.c
>> +++ b/drivers/ata/libata-core.c
>> @@ -6580,7 +6580,7 @@ static int __init ata_init(void)
>>   {
>>   	ata_parse_force_param();
>>
>> -	ata_wq = create_workqueue("ata");
>> +	ata_wq = create_lazy_workqueue("ata");
>>   	if (!ata_wq)
>>   		goto free_force_tbl;
>
> No objections to the code, operationally...
>
> But it is disappointing that the "1 thread on UP" problem is not solved  
> while changing this libata area.  Is there no way to specify a minimum  
> lazy-thread count?
>
> A key problem continues to be tying to the number of CPUs, which is  
> quite inappropriate for libata.

We'll solve that next, the first problem is reducing the per-cpu
threads. Lots of places use per-cpu workqueues because that is what is
available, not necessarily because it's an appropriate choice. Like the
ata_wq above, it's not even a good fit.

-- 
Jens Axboe

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