Chris Mason <chris.mason@xxxxxxxxxx> writes: > On Mon, Aug 23, 2010 at 10:50:31AM -0400, Christoph Hellwig wrote: >> On Mon, Aug 23, 2010 at 10:47:55AM -0400, Chris Mason wrote: >> > The aio batching code is using igrab to get an extra reference on the >> > inode so it can safely batch. igrab will go ahead and take the global >> > inode spinlock, which can be a bottleneck on large machines doing lots >> > of AIO. >> > >> > In this case, igrab isn't required because we already have a reference >> > on the file handle. It is safe to just bump the i_count directly >> > on the inode. >> > >> > Benchmarking shows this patch brings IOP/s on tons of flash up by about >> > 2.5X. >> >> There's some places in XFS where we do the same, and it showed up as a >> bottle neck before. Instead of open coding the increment we have >> a wrapper that includes and assert that the numbers is always positive. >> >> I think we really want a proper helper for general use instead of >> completly opencoding it. >> > > Nick, this is about a 1 liner to fs/aio.c replacing igrab with > atomic_inc directly on the inode reference count. > > I know your scalability tree gets rid of the global, but in this case I > think it still makes sense to avoid the locking completely when the > caller knows it is safe. Do you already have something similar hiding > in the scalability tree? I opted for the safe route, initially, as I was not too familiar with the locking. If it's deemed safe to just do the increment, that works for me. Thanks for tracking this down, Chris! Cheers, Jeff -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
