On Wed, 2013-03-06 at 20:54 +0900, Hiraku Toyooka wrote: > Hi Steven, > > (03/06/2013 12:50 AM), Steven Rostedt wrote: > > Hi Hiraku, > > > > I'm doing a lot of reconstruction of ftrace's buffering, and I'm also > > modifying a lot of the snapshot feature to work with the new stuff > > that's coming. > > > > Many thanks. I'm trying your multi-buffer patches.
And I have many more to come :-) > > > I'm looking at the -EINVAL when you write something other than '0' or > > '1' into the snapshot file when the snapshot is not allocated. I'm > > thinking that it should just return as if it succeeded. I don't > > understand why it should return -EINVAL? > > > > I thought that it might be a little strange if the clear operation > succeeded in spite of the non-allocated buffer. > (Actually, I simply implemented as you said, though.) Yeah, I may have been the one to bring it up, but I was wrong. After playing with it, it doesn't make sense. > > But I don't have trouble even if it succeeds, so I'll modify the I/F > to make it return successfully. > > > Now if you want to know if the snapshot is allocated or not, I have a > > patch that shows how to use the snapshot feature when the snapshot is > > empty, and also give the status of the snapshot itself: > > > > [root] # cat /debug/tracing/snapshot > > # tracer: nop > > # > > # > > # * Snapshot is freed * > > # > > # Snapshot commands: > > # echo 0 > snapshot : Clears and frees snapshot buffer > > # echo 1 > snapshot : Allocates snapshot buffer, if not already > > allocated. > > # Takes a snapshot of the main buffer. > > # echo 2 > snapshot : Clears snapshot buffer (but does not allocate) > > # (Doesn't have to be '2' works with any number > > that > > # is not a '0' or '1') > > > > [root] # echo 1 > /debug/tracing/snapshot > > [root] # echo 2 > /debug/tracing/snapshot > > [root] # cat /debug/tracing/snapshot > > # tracer: nop > > # > > # > > # * Snapshot is allocated * > > # > > # Snapshot commands: > > # echo 0 > snapshot : Clears and frees snapshot buffer > > # echo 1 > snapshot : Allocates snapshot buffer, if not already > > allocated. > > # Takes a snapshot of the main buffer. > > # echo 2 > snapshot : Clears snapshot buffer (but does not allocate) > > # (Doesn't have to be '2' works with any number > > that > > # is not a '0' or '1') > > > > This seems good for me and also users. > > > > > As this is a new feature for 3.9, and we are still in -rc1, I think this > > might be a good thing to add now. As well as not returning -EINVAL on > > writing to the file when the snapshot buffer isn't allocated. > > > > What do you think? > > > > I think it's OK. > I'll send a patch to make the file not return -EINVAL. Does it need to > be based on 3.9-rc1 or tip tree? I already have a patch. I'll send it out later today, and perhaps you can give me your "Acked-by". Thanks, -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/