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 > > > > > > > > > > > > > > > >
