From: David Laight <David.Laight@ACULAB.COM>
To: 'Vitaly Wool' <vitaly.wool@konsulko.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>
Subject: RE: [PATCH 6/9] mm/z3fold: move decrement of pool->pages_nr into __release_z3fold_page()
Date: Wed, 2 Mar 2022 09:12:02 +0000 [thread overview]
Message-ID: <bd5c8187c4034016a22977c9ca54c1b0@AcuMS.aculab.com> (raw)
In-Reply-To: <CAM4kBBLoaESLRr28kZ901e-nikDbnQnUu9h47OsA2phxp-pvuA@mail.gmail.com>
> > Atomic operations aren't magic.
> > Atomic operations are (at best) one slow locked bus cycle.
> > Acquiring a lock is the same.
> > Releasing a lock might be cheaper, but is probably a locked bus cycle.
> >
> > So if you use state_lock to protect pages_nr then you lose an atomic
> > operation for the decrement and gain one (for the unlock) in the increment.
> > That is even or maybe a slight gain.
> > OTOH a 64bit atomic is a PITA on some 32bit systems.
> > (In fact any atomic is a PITA on sparc32.)
>
> It's actually *stale_lock* and it's very misleading to use it for this.
> I would actually like to keep atomics but I have no problem with
> making it 32-bit for 32-bit systems. Would that work for you guys?
It would be better to rename the lock.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-03-02 9:12 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-19 9:25 [PATCH 0/9] A few cleanup patches for z3fold Miaohe Lin
2022-02-19 9:25 ` [PATCH 1/9] mm/z3fold: declare z3fold_mount with __init Miaohe Lin
2022-03-02 8:17 ` Vitaly Wool
2022-02-19 9:25 ` [PATCH 2/9] mm/z3fold: remove obsolete comment in z3fold_alloc Miaohe Lin
2022-03-02 8:18 ` Vitaly Wool
2022-02-19 9:25 ` [PATCH 3/9] mm/z3fold: minor clean up for z3fold_free Miaohe Lin
2022-03-02 8:21 ` Vitaly Wool
2022-02-19 9:25 ` [PATCH 4/9] mm/z3fold: remove unneeded page_mapcount_reset and ClearPagePrivate Miaohe Lin
2022-03-02 8:22 ` Vitaly Wool
2022-02-19 9:25 ` [PATCH 5/9] mm/z3fold: remove confusing local variable l reassignment Miaohe Lin
2022-03-02 8:24 ` Vitaly Wool
2022-02-19 9:25 ` [PATCH 6/9] mm/z3fold: move decrement of pool->pages_nr into __release_z3fold_page() Miaohe Lin
2022-02-19 16:33 ` David Laight
2022-02-21 2:53 ` Miaohe Lin
2022-02-21 5:17 ` David Laight
2022-02-21 11:37 ` Miaohe Lin
2022-03-02 8:31 ` Vitaly Wool
2022-03-02 9:12 ` David Laight [this message]
2022-03-02 10:19 ` Vitaly Wool
2022-03-03 2:27 ` Miaohe Lin
2022-02-19 9:25 ` [PATCH 7/9] mm/z3fold: remove redundant list_del_init of zhdr->buddy in z3fold_free Miaohe Lin
2022-03-02 8:38 ` Vitaly Wool
2022-02-19 9:25 ` [PATCH 8/9] mm/z3fold: remove unneeded PAGE_HEADLESS check in free_handle() Miaohe Lin
2022-02-19 9:25 ` [PATCH 9/9] mm/z3fold: remove unneeded return value of z3fold_compact_page() Miaohe Lin
2022-02-19 20:37 ` Souptick Joarder
2022-03-02 8:40 ` Vitaly Wool
2022-03-02 8:56 ` Miaohe Lin
2022-03-01 13:03 ` [PATCH 0/9] A few cleanup patches for z3fold Miaohe Lin
2022-03-01 17:36 ` Andrew Morton
2022-03-02 1:54 ` Miaohe Lin
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