From: Jens Axboe <axboe@kernel.dk>
To: Brian King <brking@linux.vnet.ibm.com>, linux-block@vger.kernel.org
Cc: dm-devel@redhat.com, snitzer@redhat.com, agk@redhat.com
Subject: Re: [PATCH 1/1] block: Convert hd_struct in_flight from atomic to percpu
Date: Wed, 28 Jun 2017 15:59:46 -0600 [thread overview]
Message-ID: <1ad262f4-2aa9-1127-3246-ce5ce80e9f4f@kernel.dk> (raw)
In-Reply-To: <9360a4b6-71be-6486-27f0-483180184905@kernel.dk>
On 06/28/2017 03:54 PM, Jens Axboe wrote:
> On 06/28/2017 03:12 PM, Brian King wrote:
>> -static inline int part_in_flight(struct hd_struct *part)
>> +static inline unsigned long part_in_flight(struct hd_struct *part)
>> {
>> - return atomic_read(&part->in_flight[0]) + atomic_read(&part->in_flight[1]);
>> + return part_stat_read(part, in_flight[0]) + part_stat_read(part, in_flight[1]);
>
> One obvious improvement would be to not do this twice, but only have to
> loop once. Instead of making this an array, make it a structure with a
> read and write count.
>
> It still doesn't really fix the issue of someone running on a kernel
> with a ton of possible CPUs configured. But it does reduce the overhead
> by 50%.
Or something as simple as this:
#define part_stat_read_double(part, field1, field2) \
({ \
typeof((part)->dkstats->field1) res = 0; \
unsigned int _cpu; \
for_each_possible_cpu(_cpu) { \
res += per_cpu_ptr((part)->dkstats, _cpu)->field1; \
res += per_cpu_ptr((part)->dkstats, _cpu)->field2; \
} \
res; \
})
static inline unsigned long part_in_flight(struct hd_struct *part)
{
return part_stat_read_double(part, in_flight[0], in_flight[1]);
}
--
Jens Axboe
next prev parent reply other threads:[~2017-06-28 21:59 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-28 21:12 [PATCH 1/1] block: Convert hd_struct in_flight from atomic to percpu Brian King
2017-06-28 21:49 ` Jens Axboe
2017-06-28 21:49 ` Jens Axboe
2017-06-28 22:04 ` Brian King
2017-06-28 22:04 ` Brian King
2017-06-29 8:40 ` Ming Lei
2017-06-29 15:58 ` Jens Axboe
2017-06-29 16:00 ` Jens Axboe
2017-06-29 18:42 ` Jens Axboe
2017-06-30 1:20 ` Ming Lei
2017-06-30 2:17 ` Jens Axboe
2017-06-30 13:05 ` [dm-devel] " Brian King
2017-06-30 13:05 ` Brian King
2017-06-30 14:08 ` [dm-devel] " Jens Axboe
2017-06-30 18:33 ` Brian King
2017-06-30 23:23 ` Ming Lei
2017-06-30 23:26 ` Jens Axboe
2017-07-01 2:18 ` Brian King
2017-07-04 1:20 ` Ming Lei
2017-07-04 20:58 ` Brian King
2017-07-01 4:17 ` Jens Axboe
2017-07-01 4:59 ` Jens Axboe
2017-07-01 16:43 ` Jens Axboe
2017-07-04 20:55 ` Brian King
2017-07-04 21:57 ` Jens Axboe
2017-06-29 16:25 ` Ming Lei
2017-06-29 17:31 ` Brian King
2017-06-30 1:08 ` Ming Lei
2017-06-30 1:08 ` Ming Lei
2017-06-28 21:54 ` Jens Axboe
2017-06-28 21:54 ` Jens Axboe
2017-06-28 21:59 ` Jens Axboe [this message]
2017-06-28 22:07 ` [dm-devel] " Brian King
2017-06-28 22:19 ` Jens Axboe
2017-06-29 12:59 ` Brian King
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