Rick Macklem wrote this message on Tue, Jul 08, 2014 at 16:10 -0400: > I tried: > m = m_getjcl(M_NOWAIT..M_JUMPAGESIZE); > if (m == NULL) > m = getjcl(M_WAITOK..MCLBYTES); > when I was experimenting with MJUMPAGESIZE clusters for NFS and what happened > was the thread looped in the first m_getjcl() instead of returning NULL. > It is about 12 layers of function calls deep and most fail/return NULL, but > somewhere one of them decides to "try again". I didn't locate the location > of that and don't know if it would be safe to change it so that m_getjcl() > returns NULL for this case. So, I took a quick look at this, and I see a weird issue... In mb_ctor_mbuf in kern_mbuf.c, the how argument is passed to m_init instead of flags... how and flags SHOULD be the same, but it could be that uma could change how to something else and we are loosing _NOWAIT.. Also, m_getjcl is calling two different uma_zalloc_arg's, know which one would be useful... You should be able to verify this w/ dtrace pretty easily in your case.. Brief call path: m_getjcl -> uma_zalloc_arg -> mb_ctor_mbuf -> m_init -> m_pkthdr_init -> mac_mbuf_init -> m_tag_get or mac_mbuf_tag_init... I didn't trace it down beyond mac_mbuf_init.. Verifying that mac_mbuf_init still has M_NOWAIT would be good... -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."Received on Wed Jul 23 2014 - 21:31:42 UTC
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