hbase-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Gary Helmling <ghelml...@gmail.com>
Subject Re: Coprocessor tax?
Date Tue, 01 Mar 2011 20:59:09 GMT
Sure, even better (it's doing the locking for you).


On Tue, Mar 1, 2011 at 12:49 PM, Ryan Rawson <ryanobjc@gmail.com> wrote:

> I don't think we need a lock even for updating, check it copy on write
> array list.
> On Mar 1, 2011 12:45 PM, "Gary Helmling" <ghelmling@gmail.com> wrote:
> > Yeah, I was just looking at the write lock references as well.
> >
> > I'm not sure RegionCoprocessorHost.preClose() would really need the write
> > lock? As you say, there is still a race in HRegion.doClose() between
> > preClose() completing and HRegion.lock.writeLock() being taken out, so
> other
> > methods could still be called after.
> >
> > RegionCoprocessorHost.postClose() occurs under the HRegion write lock, so
> > any read lock operations would already have to have completed by this
> point.
> > So here we wouldn't really need the coprocessor write lock either?
> >
> > It seems like we could actually drop the coprocessor lock, since
> > coprocessors are currently loaded prior to region open completing.
> >
> > Online coprocessor loading (not currently provided) could be handled in
> the
> > future by a lock just for loading, and creating a new coprocessor
> collection
> > and assigning when done.
> >
> > On Tue, Mar 1, 2011 at 12:08 PM, Ryan Rawson <ryanobjc@gmail.com> wrote:
> >
> >> My own profiling shows that a read write lock can be up to 3-6% of the
> >> CPU budget in our put/get query path. Adding another one if not
> >> necessary would probably not be good.
> >>
> >> In fact in the region coprocessor the only thing the write lock is
> >> used for is the preClose and postClose, but looking in the
> >> implementation of those methods I don't really get why this is
> >> necessary. The write lock ensures single thread access, but there is
> >> nothing that prevents other threads from calling other methods AFTER
> >> the postClose?
> >>
> >> -ryan
> >>
> >> On Tue, Mar 1, 2011 at 12:02 PM, Gary Helmling <ghelmling@gmail.com>
> >> wrote:
> >> > All the CoprocessorHost invocations should be wrapped in "if (cpHost
> !=
> >> > null)". We could just added an extra check for whether any
> coprocessors
> >> are
> >> > loaded -- "if (cpHost != null && cpHost.isActive())", something
like
> >> that?
> >> > Or the CoprocessorHost methods could do this checking internally.
> >> >
> >> > Either way should be relatively easy to bypass the lock acquisition.
> Is
> >> > there much overhead to acquiring a read lock if the write lock is
> never
> >> > taken though? (just wondering)
> >> >
> >> >
> >> >
> >> > On Tue, Mar 1, 2011 at 11:51 AM, Stack <stack@duboce.net> wrote:
> >> >
> >> >> So, I'm debugging something else but thread dumping I see a bunch of
> >> this:
> >> >>
> >> >>
> >> >> "IPC Server handler 6 on 61020" daemon prio=10 tid=0x00000000422d2800
> >> >> nid=0x7714 runnable [0x00007f1c5acea000]
> >> >> java.lang.Thread.State: RUNNABLE
> >> >> at
> >> >>
> >>
> java.util.concurrent.locks.ReentrantReadWriteLock$Sync.fullTryAcquireShared(ReentrantReadWriteLock.java:434)
> >> >> at
> >> >>
> >>
> java.util.concurrent.locks.ReentrantReadWriteLock$Sync.tryAcquireShared(ReentrantReadWriteLock.java:404)
> >> >> at
> >> >>
> >>
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(AbstractQueuedSynchronizer.java:1260)
> >> >> at
> >> >>
> >>
> java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.lock(ReentrantReadWriteLock.java:594)
> >> >> at
> >> >>
> >>
> org.apache.hadoop.hbase.regionserver.RegionCoprocessorHost.prePut(RegionCoprocessorHost.java:532)
> >> >> at
> >> >>
> >>
> org.apache.hadoop.hbase.regionserver.HRegion.doMiniBatchPut(HRegion.java:1476)
> >> >> at
> >> >> org.apache.hadoop.hbase.regionserver.HRegion.put(HRegion.java:1454)
> >> >> at
> >> >>
> >>
> org.apache.hadoop.hbase.regionserver.HRegionServer.multi(HRegionServer.java:2652)
> >> >> at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> >> >> at
> >> >>
> >>
> sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
> >> >> at
> >> >>
> >>
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> >> >> at java.lang.reflect.Method.invoke(Method.java:597)
> >> >> at
> >> >>
> >>
> org.apache.hadoop.hbase.ipc.WritableRpcEngine$Server.call(WritableRpcEngine.java:309)
> >> >> at
> >> >>
> >>
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1060)
> >> >>
> >> >>
> >> >> Do others? I don't have any CPs loaded. I'm wondering if we can do
> >> >> more to just avoid the CP codepath if no CPs loaded.
> >> >>
> >> >> St.Ack
> >> >>
> >> >
> >>
>

Mime
  • Unnamed multipart/alternative (inline, None, 0 bytes)
View raw message