From: Mike Snitzer <snitzer@redhat.com>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: dm-devel@redhat.com, Frank Mayhar <fmayhar@google.com>
Subject: Re: [PATCH 6/7] dm: track the maximum number of bios in a cloned request
Date: Thu, 12 Sep 2013 19:09:11 -0400 [thread overview]
Message-ID: <20130912230911.GB31577@redhat.com> (raw)
In-Reply-To: <alpine.LRH.2.02.1309121851160.31794@file01.intranet.prod.int.rdu2.redhat.com>
On Thu, Sep 12 2013 at 6:55pm -0400,
Mikulas Patocka <mpatocka@redhat.com> wrote:
> There's a race condition (it's not serious):
>
> + if (num_bios > ACCESS_ONCE(peak_rq_based_ios))
> + ACCESS_ONCE(peak_rq_based_ios) = num_bios;
>
> You can double-check it using code like this:
> if (num_bios > ACCESS_ONCE(peak_rq_based_ios)) {
> spin_lock_irqsave(&peak_rq_based_ios_lock, flags);
> if (num_bios > peak_rq_based_ios)
> peak_rq_based_ios = num_bios;
> spin_unlock_irqrestore(&peak_rq_based_ios_lock, flags);
> }
Yeah I thought about using double checked locking but didn't want to
incur the extra locking. Figured precise answer for peak_rq_based_ios
wasn't of utmost importance. But I'll think about doing it.
> Maybe - reset the value peak_rq_based_ios if the user clears
> track_peak_rq_based_ios?
Well until patch 7 there isn't a convenient place to trap the change.
And you already took issue with how I did it in that patch.
next prev parent reply other threads:[~2013-09-12 23:09 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-09 17:48 [PATCH] dm: Make MIN_IOS, et al, tunable via sysctl Frank Mayhar
2013-08-13 16:41 ` Frank Mayhar
2013-08-16 22:58 ` Frank Mayhar
2013-08-17 12:30 ` [dm-devel] " Alasdair G Kergon
2013-08-19 13:40 ` Mike Snitzer
2013-08-19 15:04 ` Frank Mayhar
2013-08-19 14:00 ` Mike Snitzer
2013-08-19 14:00 ` Mike Snitzer
2013-08-19 17:54 ` [dm-devel] " Frank Mayhar
2013-08-19 18:15 ` Mike Snitzer
2013-08-20 21:44 ` [dm-devel] " Mikulas Patocka
2013-08-20 21:52 ` Frank Mayhar
2013-08-20 21:41 ` Mikulas Patocka
2013-08-20 21:22 ` [dm-devel] [PATCH] " Mikulas Patocka
2013-08-20 21:28 ` Frank Mayhar
2013-08-20 21:47 ` Mikulas Patocka
2013-08-20 21:57 ` Frank Mayhar
2013-08-20 22:24 ` Mike Snitzer
2013-08-20 22:52 ` Mikulas Patocka
2013-08-20 23:14 ` Frank Mayhar
2013-08-22 17:26 ` Frank Mayhar
2013-08-26 14:28 ` Mikulas Patocka
2013-09-12 22:24 ` [PATCH 0/7] dm: allow mempool and bioset reserves to be tuned Mike Snitzer
2013-09-12 22:24 ` [PATCH 1/7] dm: lower bio-based mempool reservation Mike Snitzer
2013-09-12 22:40 ` Mikulas Patocka
2013-09-12 22:24 ` [PATCH 2/7] dm: add reserved_rq_based_ios module parameter Mike Snitzer
2013-09-12 22:45 ` Mikulas Patocka
2013-09-12 23:15 ` Mike Snitzer
2013-09-12 23:27 ` Mikulas Patocka
2013-09-12 23:32 ` Mike Snitzer
2013-09-12 22:24 ` [PATCH 3/7] dm: add reserved_bio_based_ios " Mike Snitzer
2013-09-12 22:47 ` Mikulas Patocka
2013-09-12 23:11 ` Mike Snitzer
2013-09-12 23:17 ` Mikulas Patocka
2013-09-18 15:17 ` Frank Mayhar
2013-09-12 22:24 ` [PATCH 4/7] dm io: use dm_get_reserved_bio_based_ios to size reserves Mike Snitzer
2013-09-12 22:48 ` Mikulas Patocka
2013-09-12 22:24 ` [PATCH 5/7] dm mpath: use dm_get_reserved_rq_based_ios to size mempool Mike Snitzer
2013-09-12 22:48 ` Mikulas Patocka
2013-09-12 22:24 ` [PATCH 6/7] dm: track the maximum number of bios in a cloned request Mike Snitzer
2013-09-12 22:55 ` Mikulas Patocka
2013-09-12 23:09 ` Mike Snitzer [this message]
2013-09-12 22:24 ` [PATCH 7/7] dm: optimize clone_rq() when track_peak_rq_based_ios is disabled Mike Snitzer
2013-09-12 23:00 ` Mikulas Patocka
2013-09-12 23:06 ` Mike Snitzer
2013-09-12 23:30 ` Mikulas Patocka
2013-09-12 23:53 ` Mike Snitzer
2013-09-13 4:46 ` Jun'ichi Nomura
2013-09-13 13:04 ` Mike Snitzer
2013-09-13 14:34 ` Mikulas Patocka
2013-09-13 18:59 ` [PATCH v2 0/3] dm: allow mempool and bioset reserves to be tuned Mike Snitzer
2013-09-13 18:59 ` [PATCH v2 1/3] dm: lower bio-based mempool reservation Mike Snitzer
2013-09-13 18:59 ` [PATCH v2 2/3] dm: add reserved_rq_based_ios module parameter Mike Snitzer
2013-09-13 18:59 ` [PATCH v2 3/3] dm: add reserved_bio_based_ios " Mike Snitzer
2013-09-13 19:22 ` [PATCH v2 0/3] dm: allow mempool and bioset reserves to be tuned Mike Snitzer
2013-09-13 20:30 ` Mike Snitzer
2013-09-13 21:08 ` [PATCH v3 " Mike Snitzer
2013-09-13 21:08 ` [PATCH v3 1/3] dm: lower bio-based mempool reservation Mike Snitzer
2013-09-13 21:08 ` [PATCH v3 2/3] dm: add reserved_rq_based_ios module parameter Mike Snitzer
2013-09-13 21:08 ` [PATCH v3 3/3] dm: add reserved_bio_based_ios " Mike Snitzer
2013-09-18 15:10 ` [PATCH v3 0/3] dm: allow mempool and bioset reserves to be tuned Frank Mayhar
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