From: Jens Axboe <axboe@kernel.dk>
To: Ming Lei <ming.lei@redhat.com>
Cc: linux-block@vger.kernel.org, "Ewan D . Milne" <emilne@redhat.com>
Subject: Re: [PATCH] lib/sbitmap: allocate sb->map via kvzalloc_node
Date: Mon, 21 Mar 2022 20:01:20 -0600 [thread overview]
Message-ID: <9e78f4fb-f7c4-3f4f-cac1-40d4ee9455d5@kernel.dk> (raw)
In-Reply-To: <YjkXenfaI7iSewSC@T590>
On 3/21/22 6:25 PM, Ming Lei wrote:
> Hello,
>
> On Wed, Mar 16, 2022 at 09:27:08AM +0800, Ming Lei wrote:
>> sbitmap has been used in scsi for replacing atomic operations on
>> sdev->device_busy, so IOPS on some fast scsi storage can be improved.
>>
>> However, sdev->device_busy can be changed in fast path, so we have to
>> allocate the sb->map statically. sdev->device_busy has been capped to 1024,
>> but some drivers may configure the default depth as < 8, then
>> cause each sbitmap word to hold only one bit. Finally 1024 * 128(
>> sizeof(sbitmap_word)) bytes is needed for sb->map, given it is order 5
>> allocation, sometimes it may fail.
>>
>> Avoid the issue by using kvzalloc_node() for allocating sb->map.
>>
>> Cc: Ewan D. Milne <emilne@redhat.com>
>> Signed-off-by: Ming Lei <ming.lei@redhat.com>
>
> Ping...
Was waiting on a response to the question on why we don't make this
dependent on size, but upon look at kvzalloc_node(), this is already
what it does. So I guess this looks fine to me too.
--
Jens Axboe
next prev parent reply other threads:[~2022-03-22 2:01 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-16 1:27 [PATCH] lib/sbitmap: allocate sb->map via kvzalloc_node Ming Lei
2022-03-16 2:54 ` Chaitanya Kulkarni
2022-03-22 0:25 ` Ming Lei
2022-03-22 2:01 ` Jens Axboe [this message]
2022-03-22 2:52 ` Jens Axboe
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