svn commit: r189374 - user/kmacy/HEAD_fast_net_merge/sys/netinet

[Kip Macy]

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 at 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
>