From: Andrea Arcangeli <aarcange@redhat.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>,
Andrew Morton <akpm@linux-foundation.org>,
Arthur Marsh <arthur.marsh@internode.on.net>,
Clemens Ladisch <cladisch@googlemail.com>,
Linux-MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration
Date: Sat, 26 Feb 2011 01:16:11 +0100 [thread overview]
Message-ID: <20110226001611.GA19630@random.random> (raw)
In-Reply-To: <20110225223204.GW25382@cmpxchg.org>
On Fri, Feb 25, 2011 at 11:32:04PM +0100, Johannes Weiner wrote:
> I don't understand why this conditional is broken up like this.
> cond_resched() will have the right checks anyway. Okay, you would
> save fatal_signal_pending() in the 'did one cluster' case. Is it that
> expensive? Couldn't this be simpler like
>
> did_cluster = ((low_pfn + 1) % SWAP_CLUSTER_MAX) == 0
> lock_contended = spin_is_contended(&zone->lru_lock);
> if (did_cluster || lock_contended || need_resched()) {
> spin_unlock_irq(&zone->lru_lock);
> cond_resched();
> spin_lock_irq(&zone->lru_lock);
> if (fatal_signal_pending(current))
> break;
> }
>
> instead?
If we don't release irqs first, how can need_resched get set in the
first place if the local apic irq can't run? I guess that's why
there's no cond_resched_lock_irq. BTW, I never liked too much clearing
interrupts for locks that can't ever be taken from irq (it's a
scalability boost to reduce contention but it makes things like above
confusing and it increases irq latency a bit.
WARNING: multiple messages have this Message-ID (diff)
From: Andrea Arcangeli <aarcange@redhat.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>,
Andrew Morton <akpm@linux-foundation.org>,
Arthur Marsh <arthur.marsh@internode.on.net>,
Clemens Ladisch <cladisch@googlemail.com>,
Linux-MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration
Date: Sat, 26 Feb 2011 01:16:11 +0100 [thread overview]
Message-ID: <20110226001611.GA19630@random.random> (raw)
In-Reply-To: <20110225223204.GW25382@cmpxchg.org>
On Fri, Feb 25, 2011 at 11:32:04PM +0100, Johannes Weiner wrote:
> I don't understand why this conditional is broken up like this.
> cond_resched() will have the right checks anyway. Okay, you would
> save fatal_signal_pending() in the 'did one cluster' case. Is it that
> expensive? Couldn't this be simpler like
>
> did_cluster = ((low_pfn + 1) % SWAP_CLUSTER_MAX) == 0
> lock_contended = spin_is_contended(&zone->lru_lock);
> if (did_cluster || lock_contended || need_resched()) {
> spin_unlock_irq(&zone->lru_lock);
> cond_resched();
> spin_lock_irq(&zone->lru_lock);
> if (fatal_signal_pending(current))
> break;
> }
>
> instead?
If we don't release irqs first, how can need_resched get set in the
first place if the local apic irq can't run? I guess that's why
there's no cond_resched_lock_irq. BTW, I never liked too much clearing
interrupts for locks that can't ever be taken from irq (it's a
scalability boost to reduce contention but it makes things like above
confusing and it increases irq latency a bit.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-02-26 0:16 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-25 20:04 [PATCH 0/2] Reduce the amount of time compaction disables IRQs for V2 Mel Gorman
2011-02-25 20:04 ` Mel Gorman
2011-02-25 20:04 ` [PATCH 1/2] mm: compaction: Minimise the time IRQs are disabled while isolating free pages Mel Gorman
2011-02-25 20:04 ` Mel Gorman
2011-02-25 22:34 ` Johannes Weiner
2011-02-25 22:34 ` Johannes Weiner
2011-02-28 1:55 ` KAMEZAWA Hiroyuki
2011-02-28 1:55 ` KAMEZAWA Hiroyuki
2011-02-28 22:08 ` Minchan Kim
2011-02-28 22:08 ` Minchan Kim
2011-02-25 20:04 ` [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration Mel Gorman
2011-02-25 20:04 ` Mel Gorman
2011-02-25 22:32 ` Johannes Weiner
2011-02-25 22:32 ` Johannes Weiner
2011-02-26 0:16 ` Andrea Arcangeli [this message]
2011-02-26 0:16 ` Andrea Arcangeli
2011-02-28 2:17 ` KAMEZAWA Hiroyuki
2011-02-28 2:17 ` KAMEZAWA Hiroyuki
2011-02-28 5:48 ` Andrea Arcangeli
2011-02-28 5:48 ` Andrea Arcangeli
2011-02-28 5:54 ` KAMEZAWA Hiroyuki
2011-02-28 5:54 ` KAMEZAWA Hiroyuki
2011-02-28 9:28 ` Mel Gorman
2011-02-28 9:28 ` Mel Gorman
2011-02-28 9:42 ` KAMEZAWA Hiroyuki
2011-02-28 9:42 ` KAMEZAWA Hiroyuki
2011-02-28 10:18 ` Mel Gorman
2011-02-28 10:18 ` Mel Gorman
2011-02-28 23:42 ` KAMEZAWA Hiroyuki
2011-02-28 23:42 ` KAMEZAWA Hiroyuki
2011-03-01 4:11 ` Minchan Kim
2011-03-01 4:11 ` Minchan Kim
2011-03-01 4:49 ` KAMEZAWA Hiroyuki
2011-03-01 4:49 ` KAMEZAWA Hiroyuki
2011-02-28 23:01 ` Minchan Kim
2011-02-28 23:01 ` Minchan Kim
2011-02-28 23:07 ` Andrea Arcangeli
2011-02-28 23:07 ` Andrea Arcangeli
2011-02-28 23:25 ` Minchan Kim
2011-02-28 23:25 ` Minchan Kim
2011-03-01 22:15 ` Andrew Morton
2011-03-01 22:15 ` Andrew Morton
2011-02-25 20:07 ` [PATCH 0/2] Reduce the amount of time compaction disables IRQs for V2 Andrea Arcangeli
2011-02-25 20:07 ` Andrea Arcangeli
-- strict thread matches above, loose matches on Subject: below --
2011-03-01 15:35 [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration Minchan Kim
2011-03-01 15:35 ` Minchan Kim
2011-03-01 16:19 ` Andrea Arcangeli
2011-03-01 16:19 ` Andrea Arcangeli
2011-03-01 22:22 ` Minchan Kim
2011-03-01 22:22 ` Minchan Kim
2011-03-01 22:34 ` Andrew Morton
2011-03-01 22:34 ` Andrew Morton
2011-03-01 22:57 ` Minchan Kim
2011-03-01 22:57 ` Minchan Kim
2011-02-25 18:00 [PATCH 0/2] Reduce the amount of time compaction disables IRQs for Mel Gorman
2011-02-25 18:00 ` [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration Mel Gorman
2011-02-25 18:00 ` Mel Gorman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110226001611.GA19630@random.random \
--to=aarcange@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=arthur.marsh@internode.on.net \
--cc=cladisch@googlemail.com \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mel@csn.ul.ie \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.