+1 Great work.
Thanks, Penghui On Wed, Feb 23, 2022 at 8:56 PM Enrico Olivelli <eolive...@gmail.com> wrote: > Cool > > I also observed such problems but I haven't time to work on a proposal. > > Looking forward to see your patch > > > Enrico > > Il Mer 23 Feb 2022, 10:43 Jiuming Tao <jm...@streamnative.io.invalid> ha > scritto: > > > Hi all, > > > > 1. I have learned that the /metrics endpoint will be requested by more > than > > one metrics collect system. In the condition, I want to reimplement > > `PromethuesMetricsServlet` by sliding window. > > PrometheusMetricsGenerator#generate will be invoked once in a period(such > > as 1 minute), the result will be cached and returned for every metrics > > collect request in the period directly. It could save memory and avoid > high > > CPU usage. > > > > 2. When there are hundreds MB metrics data collected, it causes high heap > > memory usage, high CPU usage and GC pressure. In the > > `PrometheusMetricsGenerator#generate` method, it uses > > `ByteBufAllocator.DEFAULT.heapBuffer()` to allocate memory for writing > > metrics data. The default size of `ByteBufAllocator.DEFAULT.heapBuffer()` > > is 256 bytes, when the buffer resizes, the new buffer capacity is 512 > > bytes(power of 2) and with `mem_copy` operation. > > If I want to write 100 MB data to the buffer, the current buffer size is > > 128 MB, and the total memory usage is close to 256 MB (256bytes + 512 > bytes > > + 1k + .... + 64MB + 128MB). When the buffer size is greater than netty > > buffer chunkSize(16 MB), it will be allocated as UnpooledHeapByteBuf in > the > > heap. After writing metrics data into the buffer, return it to the client > > by jetty, jetty will copy it into jetty's buffer with memory allocation > in > > the heap, again! > > In this condition, for the purpose of saving memory, avoid high CPU > > usage(too much memory allocations and `mem_copy` operations) and reducing > > GC pressure, I want to change `ByteBufAllocator.DEFAULT.heapBuffer()` to > > `ByteBufAllocator.DEFAULT.compositeDirectBuffer()`, it wouldn't cause > > `mem_copy` operations and huge memory allocations(CompositeDirectByteBuf > is > > a bit slowly in read/write, but it's worth). After writing data, I will > > call the `HttpOutput#write(ByteBuffer)` method and write it to the > client, > > the method won't cause `mem_copy` (I have to wrap ByteBuf to ByteBuffer, > if > > ByteBuf wrapped, there will be zero-copy). > > I tested NO.2 in my local, and it turns out performance is better than > the > > heap buffer(below images). > > > > > > > https://drive.google.com/file/d/1-0drrs9s9kZ2NbbVmzQDwPHdgtpE6QyW/view?usp=sharing > > (CompositeDirectByteBuf) > > > > > https://drive.google.com/file/d/1-0m15YdsjBudsiweZ4DO7aU3bOFeK17w/view?usp=sharing > > (PooledHeapByteBuf) > > > > Thanks, > > Tao Jiuming > > >
