Date: Wed, 4 Mar 2009 15:20:55 -0800 From: Kip Macy <kmacy@freebsd.org> To: John Baldwin <jhb@freebsd.org> Cc: src-committers@freebsd.org, svn-src-user@freebsd.org Subject: Re: svn commit: r189374 - user/kmacy/HEAD_fast_net_merge/sys/netinet Message-ID: <3c1674c90903041520o145b0c42uc1dd2d41870432e6@mail.gmail.com> In-Reply-To: <200903041759.31535.jhb@freebsd.org> References: <200903042122.n24LMdO3053650@svn.freebsd.org> <200903041759.31535.jhb@freebsd.org>
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Do we have any mechanism for handling sparse cpuids? If so I can do modulo the number of active cpus and then taking that value as an index. If not its a bit of an academic observation. -Kip On Wed, Mar 4, 2009 at 2:59 PM, John Baldwin <jhb@freebsd.org> wrote: > On Wednesday 04 March 2009 4:22:39 pm Kip Macy wrote: >> Author: kmacy >> Date: Wed Mar 4 21:22:39 2009 >> New Revision: 189374 >> URL: http://svn.freebsd.org/changeset/base/189374 >> >> Log: >> Use per-cpu callouts for tcp_timer >> 186694, 187660 >> >> 186694: >> - convert tcp_timer_activate over to using >> per-cpu callouts >> - don't acquire the tcbinfo lock exclusively >> in tcp_timer_rexmt unless needed for tcp_drop >> >> 187660: >> - mp_maxid may not be valid ensure that we >> re-schedule on cpuid less than or equal to >> the current one for tcp callouts >> >> Modified: >> user/kmacy/HEAD_fast_net_merge/sys/netinet/tcp_timer.c >> >> Modified: user/kmacy/HEAD_fast_net_merge/sys/netinet/tcp_timer.c >> > ============================================================================== >> --- user/kmacy/HEAD_fast_net_merge/sys/netinet/tcp_timer.c Wed Mar 4 > 21:04:52 2009 (r189373) >> +++ user/kmacy/HEAD_fast_net_merge/sys/netinet/tcp_timer.c Wed Mar 4 > 21:22:39 2009 (r189374) >> @@ -41,6 +41,7 @@ __FBSDID("$FreeBSD$"); >> #include <sys/mbuf.h> >> #include <sys/mutex.h> >> #include <sys/protosw.h> >> +#include <sys/smp.h> >> #include <sys/socket.h> >> #include <sys/socketvar.h> >> #include <sys/sysctl.h> >> @@ -118,6 +119,8 @@ int tcp_maxpersistidle; >> /* max idle time in persist */ >> int tcp_maxidle; >> >> +#define INP_CPU(inp) min(curcpu, ((inp)->inp_flowid % mp_maxid)) > > This is not really safe. CPU ID's may be sparse. The only guarantees you > have are that 0 is the boot CPU, and that all valid CPU IDs are in the range > [0 .. mp_maxid] (inclusive). Thus, you could have a system that only has > CPUs 0 and 3 and if you are on CPU 3 and flowid is 5, then this will choose > min(3, 5 % 3) == min(3, 2) == 2 which is an invalid CPU. > > -- > John Baldwin >help
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