A [hopefully] conforming style(9) revamp of mb_alloc and related code.
(This was possible due to bde's remarkable patience.)
Submitted by: (in large part) bde
Reviewed by: (the other part) bde
you run out of mbuf address space.
kern/subr_mbuf.c: print a warning message when mb_alloc fails, again
rate-limited to at most once per second. This covers other
cases of mbuf allocation failures. Probably it also overlaps the
one handled in vm/vm_kern.c, so maybe the latter should go away.
This warning will let us gradually remove the printf that are scattered
across most network drivers to report mbuf allocation failures.
Those are potentially dangerous, in that they are not rate-limited and
can easily cause systems to panic.
Unless there is disagreement (which does not seem to be the case
judging from the discussion on -net so far), and because this is
sort of a safety bugfix, I plan to commit a similar change to STABLE
during the weekend (it affects kern/uipc_mbuf.c there).
Discussed-with: jlemon, silby and -net
For an object type, we maintain a variable mb_mapfull. It is 0 by default
and is only raised to 1 in one place: when an mb_pop_cont() fails for
the first time, on the assumption that the reason for the failure is
due to the underlying map for the object (e.g. clust_map, mbuf_map) being
exhausted.
Problem and Changes:
Change how we define "mb_mapfull." It now means: "set to 1 when the first
mb_pop_cont() fails only in the kmem_malloc()-ing of the object, and
only if the call was with the M_TRYWAIT flag." This is a more conservative
definition and should avoid odd [but theoretically possible] situations
from occuring. i.e. we had set mb_mapfull to 1 thinking the map for the
object was actually exhausted when we _actually_ failed in malloc()ing
the space for the bucket structure managing the objects in the page
we're allocating.
when I changed the allocator bits. This implements per-CPU mbtypes
stats by keeping net number of decrements/increments of a given mbtype
per-CPU and then summing all of the per-CPU mbtypes to produce the total
net number of allocated mbufs of the given mbtype.
Counters are carefully balanced to avoid/prevent underflows/overflows.
mbtypes stats are re-enabled with the idea that we may occasionally
(although very rarely) observe slight inconsistencies in the stat
reporting. Most of the time, we should be fine, though.
Also make appropriate modifications to netstat(1) and systat(1) to do
the necessary reporting.
Submitted by: Jiangyi Liu <jyliu@163.net>
Note ALL MODULES MUST BE RECOMPILED
make the kernel aware that there are smaller units of scheduling than the
process. (but only allow one thread per process at this time).
This is functionally equivalent to teh previousl -current except
that there is a thread associated with each process.
Sorry john! (your next MFC will be a doosie!)
Reviewed by: peter@freebsd.org, dillon@freebsd.org
X-MFC after: ha ha ha ha
order to avoid namespace collision with subr_mchain.c's mb_init(). This
wasn't "fatal" as the mbuf initialization routine mb_init() was local to
subr_mbuf.c which in turn didn't pull in subr_mchain.c's mb_init()
declaration, but it should deffinately be changed now before it creates
headache.
defined to 0 in the non-SMP case, which very much makes sense as it
permits its usage in per-CPU initialization loops (for an example, check
out subr_mbuf.c).
Further, on a UP system, make mb_alloc always use the first per-CPU
container, regardless of cpuid (i.e. remove reliability on cpuid in the
UP case).
Requested by: alfred
initialize in the right order to make derivative settings work right.
eg: at compile time, nmbufs was double nmbclusters. For POLA this should
work the same at runtime.
were indices in a dense array. The cpuids are a sparse set and treat
them as such, setting up containers only for CPUs activated during
mb_init().
- Fix netstat(1) and systat(1) to treat the per-CPU stats area as a sparse
map, in accordance with the above.
This allows us to properly boot with certain CPUs disactivated. However, if
we later decide to re-activate said CPUs, we will barf until we decide to
implement CPU spinon/spinoff callback hooks to allow for said CPUs' per-CPU
containers to get configured on their activation.
Reported by: mjacob
Partially (sys/ diffs) Submitted by: mjacob
introduce a modified allocation mechanism for mbufs and mbuf clusters; one
which can scale under SMP and which offers the possibility of resource
reclamation to be implemented in the future. Notable advantages:
o Reduce contention for SMP by offering per-CPU pools and locks.
o Better use of data cache due to per-CPU pools.
o Much less code cache pollution due to excessively large allocation macros.
o Framework for `grouping' objects from same page together so as to be able
to possibly free wired-down pages back to the system if they are no longer
needed by the network stacks.
Additional things changed with this addition:
- Moved some mbuf specific declarations and initializations from
sys/conf/param.c into mbuf-specific code where they belong.
- m_getclr() has been renamed to m_get_clrd() because the old name is really
confusing. m_getclr() HAS been preserved though and is defined to the new
name. No tree sweep has been done "to change the interface," as the old
name will continue to be supported and is not depracated. The change was
merely done because m_getclr() sounds too much like "m_get a cluster."
- TEMPORARILY disabled mbtypes statistics displaying in netstat(1) and
systat(1) (see TODO below).
- Fixed systat(1) to display number of "free mbufs" based on new per-CPU
stat structures.
- Fixed netstat(1) to display new per-CPU stats based on sysctl-exported
per-CPU stat structures. All infos are fetched via sysctl.
TODO (in order of priority):
- Re-enable mbtypes statistics in both netstat(1) and systat(1) after
introducing an SMP friendly way to collect the mbtypes stats under the
already introduced per-CPU locks (i.e. hopefully don't use atomic() - it
seems too costly for a mere stat update, especially when other locks are
already present).
- Optionally have systat(1) display not only "total free mbufs" but also
"total free mbufs per CPU pool."
- Fix minor length-fetching issues in netstat(1) related to recently
re-enabled option to read mbuf stats from a core file.
- Move reference counters at least for mbuf clusters into an unused portion
of the cluster itself, to save space and need to allocate a counter.
- Look into introducing resource freeing possibly from a kproc.
Reviewed by (in parts): jlemon, jake, silby, terry
Tested by: jlemon (Intel & Alpha), mjacob (Intel & Alpha)
Preliminary performance measurements: jlemon (and me, obviously)
URL: http://people.freebsd.org/~bmilekic/mb_alloc/
