From: Andi Kleen <andi@firstfloor•org>
To: "Patrick Mullaney" <pmullaney@novell•com>
Cc: "Gregory Haskins" <GHaskins@novell•com>, <davem@davemloft•net>,
<netdev@vger•kernel.org>
Subject: Re: [PATCH] net/core/sock.c remove extra wakeup
Date: Sun, 01 Jun 2008 23:03:41 +0200 [thread overview]
Message-ID: <87prr027gy.fsf@basil.nowhere.org> (raw)
In-Reply-To: <483FDE61020000C7000389F6@lucius.provo.novell.com> (Patrick Mullaney's message of "Fri, 30 May 2008 11:00:49 -0600")
"Patrick Mullaney" <pmullaney@novell•com> writes:
>
> Would a better approach be?
>
> 1) clear the bit when the waiter returns(bottom of sock_wait_for_wmem)
> 2) add a new wait-queue to the socket to separate the writers
> 3) another idea?
A large reason this is tricky is because it is essentially lockless. So
alternative would be:
4) you add a spinlock which is always taken around the various condition
checks and bit manipulation. Not 100% sure if it would be bad to
general SMP scalability (you would need to ensure that the bouncing
lock cache line isn't a performance problem), but at least it would
be much safer and makes it much easier to verify your change is correct.
Actually the wait queue already has such a lock, so it might not be
that expensive if you switch the wait queue to a lockless version.
-Andi
next prev parent reply other threads:[~2008-06-01 21:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <483F99090200005A00037FFE@lucius.provo.novell.com>
[not found] ` <483F990C0200005A00038001@lucius.provo.novell.com>
2008-05-30 17:00 ` [PATCH] net/core/sock.c remove extra wakeup Patrick Mullaney
2008-06-01 21:03 ` Andi Kleen [this message]
[not found] <483F99090200005A00037FFE@sinclair.provo.novell.com>
2008-05-30 10:05 ` Gregory Haskins
2008-06-11 6:46 ` Herbert Xu
2008-06-16 3:48 ` Gregory Haskins
2008-05-29 16:08 Patrick Mullaney
2008-05-30 9:52 ` David Miller
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