Thanks Shammon for your detailed response, it looks good to me. Best, Guojun
On Tue, Apr 25, 2023 at 3:28 PM Jingsong Li <[email protected]> wrote: > Thanks for explaining. > > Sounds good to me. > > 256 should be 256 MB. > > Best, > Jingsong > > On Tue, Apr 25, 2023 at 3:03 PM Shammon FY <[email protected]> wrote: > > > > Hi Jingsong & Guojun > > > > Users can config SINK_MANAGED_WRITER_BUFFER_WEIGHT in sql job, for > example > > `INSERT INTO paimon_table > > /*+ OPTIONS('sink.use-managed-memory-allocator'='true', > > 'sink.managed.writer-buffer-weight'='256') */ SELECT ... FROM ...;` > > > > Flink will calculate the memory of Managed Memory based on the weights of > > 70, 70, and 30 for the Operator, Statebackend, and Python according to > the > > requirements. After that, Flink normalizes the weight of each specific > > operator and recalculates the operator's memory from the Operator Managed > > Memory. > > > > Users can config agg/sort operator weight for Flink Batch jobs with > options > > `table.exec.resource.hash-agg.memory`, > > `table.exec.resource.hash-join.memory` and > > `table.exec.resource.sort.memory`, the default weights for them are 128. > > For window operators in Flink Streaming jobs, there are const weights > with > > value 100. > > > > Compared to these operators, I think it's sufficient to use default > weight > > 256 for sink operator. If the writer buffer is out of memory, users need > to > > increase the managed memory size. We can clearly describe it in the > > document. > > > > Best, > > Shammon FY > > > > > > On Tue, Apr 25, 2023 at 12:22 PM Jingsong Li <[email protected]> > wrote: > > > > > Looks good to me! > > > > > > On Tue, Apr 25, 2023 at 12:12 PM Shammon FY <[email protected]> wrote: > > > > > > > > Hi Jingsong > > > > > > > > I agree with you that from a performance perspective there is indeed > no > > > > need to create segments for Paimon based on Flink segments. If we > convert > > > > Flink MemorySegment to Paimon directly, I think we should remove the > > > `free` > > > > method in Paimon's `MemorySegment`: > > > > 1. As you mentioned above, Paimon won't free segment > > > > 2. Avoid users mistakenly calling free method to duplicate release > > > off-heap > > > > memory > > > > > > > > In addition, we need to declare in the Paimon's MemorySegment that > > > off-heap > > > > memory needs to be allocated and released by the engine. What do you > > > think? > > > > > > > > Best, > > > > Shammon FY > > > > > > > > > > > > On Tue, Apr 25, 2023 at 9:53 AM Jingsong Li <[email protected]> > > > wrote: > > > > > > > > > About Guojun's concerns, > > > > > > > > > > How to configure SINK_MANAGED_WRITER_BUFFER_WEIGHT? > > > > > How does it allocate memory with sort and agg? What is the best > value > > > to > > > > > assign? > > > > > > > > > > > users can configure managed memory weights for AGG and window > > > operators > > > > > for Flink jobs > > > > > > > > > > How to? > > > > > > > > > > I think we can add more explanation. > > > > > > > > > > Best, > > > > > Jingsong > > > > > > > > > > On Tue, Apr 25, 2023 at 9:46 AM Jingsong Li < > [email protected]> > > > > > wrote: > > > > > > > > > > > > Hi Shammon, > > > > > > > > > > > > But nobody released the Paimon MemorySegment. > > > > > > > > > > > > I think we can have a clear definition here, Flink's memory is > > > managed > > > > > by Flink. > > > > > > > > > > > > The introduction of interface here has a big impact on > performance, > > > > > > and Flink did a lot of testing and optimization early on to avoid > > > > > > interface invoking as much as possible. > > > > > > > > > > > > Best, > > > > > > Jingsong > > > > > > > > > > > > On Sun, Apr 23, 2023 at 5:51 PM Shammon FY <[email protected]> > > > wrote: > > > > > > > > > > > > > > Thanks for all the feedbacks. > > > > > > > > > > > > > > To Jingsong > > > > > > > > Maybe we can just use some reflection method to get > > > offHeapBuffer and > > > > > > > heapMemory from Flink MemorySegment. > > > > > > > > > > > > > > Yes, we can indeed construct a MemorySegment for Paimon in this > > > way, > > > > > but > > > > > > > this method may have duplicate release issues for the segment. > > > Assuming > > > > > > > Flink has applied for an off-heap memory, Paimon gets the > off-heap > > > > > buffer > > > > > > > and creates its MemorySegment, then the off-heap buffer will > be in > > > > > Flink > > > > > > > MemorySegment and Paimon MemorySegment. When the off-heap > buffer is > > > > > > > released in Paimon with `UNSAFE.freeMemory(this.address)`, it > may > > > be > > > > > > > released again in Flink's MemorySegment. > > > > > > > > > > > > > > To Liming > > > > > > > > Is it possible to cause a deadlock when requesting for memory > > > from > > > > > the > > > > > > > engine's managed memory? Is it necessary to add some memory > > > checking or > > > > > > > timeout mechanism here? > > > > > > > > > > > > > > Flink allocates segments for parallel tasks in MemoryManager. > When > > > the > > > > > > > usage of memory in MemoryManager hits the limit, it will throw > > > > > Exception > > > > > > > > > > > > > > To Guojun > > > > > > > > One question I'm thinking about is that will this increase > the > > > bar of > > > > > > > writing performance maintenance on Paimon? Like how to decide > an > > > > > > > appropriate memory weight for users' writing jobs. > > > > > > > > > > > > > > Currently, users can configure managed memory weights for AGG > and > > > > > window > > > > > > > operators for Flink jobs, this is similar to the writer buffer > pool > > > > > weight > > > > > > > configured in Paimon. So for Flink users, I think this will > not be > > > a > > > > > > > problem. > > > > > > > > > > > > > > Best, > > > > > > > Shammon FY > > > > > > > > > > > > > > > > > > > > > On Fri, Apr 21, 2023 at 11:42 AM Guojun Li < > > > [email protected]> > > > > > wrote: > > > > > > > > > > > > > > > Hi Shammon, > > > > > > > > > > > > > > > > Thank you for writing up the proposal. It's great to > introduce > > > this > > > > > unified > > > > > > > > memory management for Paimon! > > > > > > > > > > > > > > > > One question I'm thinking about is that will this increase > the > > > bar of > > > > > > > > writing performance maintenance on Paimon? Like how to > decide an > > > > > > > > appropriate memory weight for users' writing jobs. > > > > > > > > > > > > > > > > Thanks, > > > > > > > > Guojun > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > On Thu, Apr 20, 2023 at 8:45 PM Ming Li < > [email protected]> > > > > > wrote: > > > > > > > > > > > > > > > > > Thanks Shammon for the proposal. > > > > > > > > > > > > > > > > > > For me it is more appropriate to leave the memory > management > > > to the > > > > > > > > > computing engine. > > > > > > > > > > > > > > > > > > But I have a small question about this proposal. If the > > > engine's > > > > > memory > > > > > > > > is > > > > > > > > > not configured properly, is it possible to cause a deadlock > > > when > > > > > > > > requesting > > > > > > > > > for memory from the engine's managed memory? Is it > necessary to > > > > > add some > > > > > > > > > memory checking or timeout mechanism here? > > > > > > > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > > > > > > Ming Li > > > > > > > > > > > > > > > > > > > > > > > > > > > Shammon FY <[email protected]> 于2023年4月19日周三 09:57写道： > > > > > > > > > > > > > > > > > > > Hi devs: > > > > > > > > > > > > > > > > > > > > I would like to start a discussion of PIP-1: Improve > Shared > > > > > Writer > > > > > > > > Buffer > > > > > > > > > > Pool For Sink [1]. Currently Paimon sink task creates a > heap > > > > > memory > > > > > > > > pool > > > > > > > > > > which is shared by writers. When there are multiple > tasks in > > > an > > > > > > > > Executor, > > > > > > > > > > it may cause FullGC, performance issues and even OOM. > > > > > > > > > > > > > > > > > > > > This PIP aims to improve the buffer pool for writers in > > > Paimon > > > > > tasks. > > > > > > > > > > Paimon tasks can create memory pools based on Executor > Memory > > > > > which > > > > > > > > will > > > > > > > > > be > > > > > > > > > > managed by Executor, such as Managed Memory in Flink > > > > > TaskManager. It > > > > > > > > will > > > > > > > > > > improve the stability and performance of sinks by > managing > > > writer > > > > > > > > buffers > > > > > > > > > > for multiple tasks through Executor. > > > > > > > > > > > > > > > > > > > > Looking forward to your feedback, thanks. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > [1] > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/PAIMON/PIP-1%3A+Improve+Shared+Writer+Buffer+Pool+For+Sink > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Best, > > > > > > > > > > Shammon FY > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
