Date: Mon, 13 Sep 1999 14:40:53 -0400 (EDT) From: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> To: Bosko Milekic <bmilekic@dsuper.net> Cc: Stas Kisel <stas@sonet.crimea.ua>, avalon@coombs.anu.edu.au, freebsd-hackers@FreeBSD.ORG, freebsd-security@FreeBSD.ORG Subject: Re: mbuf shortage situations (followup) Message-ID: <199909131840.OAA31048@khavrinen.lcs.mit.edu> In-Reply-To: <Pine.OSF.4.05.9909122304470.18795-300000@oracle.dsuper.net> References: <199909091447.SAA24055@sonet.crimea.ua> <Pine.OSF.4.05.9909122304470.18795-300000@oracle.dsuper.net>
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<<On Sun, 12 Sep 1999 23:19:13 -0400 (EDT), Bosko Milekic <bmilekic@dsuper.net> said: > This message is in MIME format. The first part should be readable text, > while the remaining parts are likely unreadable without MIME-aware tools. > Send mail to mime@docserver.cac.washington.edu for more info. It would be preferable if text were sent as text, since MIME-encoded patches require more effort to read. > I'm also aware of the possiblity of some people not liking the > fact that we tsleep() forever (e.g. tsleep(x,x,x,0)). I don't have any problem with sleeping forever -- but I am concerned about the possibility of deadlock, especially when client-NFS is involved. If the problem just moves around and has harder-to-recover symptoms, the change isn't helping. The 4.3BSD code had two different behaviors: - For clusters, if M_WAIT was specified and there was no space left in mb_map, it panicked. However, m_clalloc was never called with M_WAIT, so that panic was effectively dead code. - For mbufs, if M_WAIT was specified and there were no mbufs available, it would sleep at PZERO - 1 (which was interruptible). In 4.3, the code was able to deal with cluster allocation failing. We have a somewhat different situation now, because many network interface devices have less-flexible DMA mechanisms which don't allow packet reception into non-contiguous buffers, so we need to have at least a certain number of clusters available for this purpose. -GAWollman -- Garrett A. Wollman | O Siem / We are all family / O Siem / We're all the same wollman@lcs.mit.edu | O Siem / The fires of freedom Opinions not those of| Dance in the burning flame MIT, LCS, CRS, or NSA| - Susan Aglukark and Chad Irschick To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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