Thanks Haomai.. Since Async messenger is always using a constant number of threads , there could be a potential performance problem of scaling up the client connections keeping the constant number of OSDs ? May be it's a good tradeoff.. Regards Somnath -----Original Message----- From: Haomai Wang [mailto:haomaiwang@xxxxxxxxx] Sent: Monday, October 12, 2015 11:35 PM To: Somnath Roy Cc: Mark Nelson; ceph-devel; ceph-users@xxxxxxxxxxxxxx Subject: Re: Initial performance cluster SimpleMessenger vs AsyncMessenger results On Tue, Oct 13, 2015 at 12:18 PM, Somnath Roy <Somnath.Roy@xxxxxxxxxxx> wrote: > Mark, > > Thanks for this data. This means probably simple messenger (not OSD > core) is not doing optimal job of handling memory. > > > > Haomai, > > I am not that familiar with Async messenger code base, do you have an > explanation of the behavior (like good performance with default > tcmalloc) Mark reported ? Is it using lot less thread overall than Simple ? Originally async messenger mainly want to solve with high thread number problem which limited the ceph cluster size. High context switch and cpu usage caused by simple messenger under large cluster. Recently we have memory problem discussed on ML and I also spend times to think about the root cause. Currently I would like to consider the simple messenger's memory usage is deviating from the design of tcmalloc. Tcmalloc is aimed to provide memory with local cache, and it also has memory control among all threads, if we have too much threads, it may let tcmalloc busy with memory lock contention. Async messenger uses thread pool to serve connections, it make all blocking calls in simple messenger async. > > Also, it seems Async messenger has some inefficiencies in the io path > and that’s why it is not performing as well as simple if the memory > allocation stuff is optimally handled. Yep, simple messenger use two threads(one for read, one for write) to serve one connection, async messenger at most have one thread to serve one connection and multi connection will share the same thread. Next, I would like to have several plans to improve performance: 1. add poll mode support, I hope it can help enhance high performance storage need 2. add load balance ability among worker threads 3. move more works out of messenger thread. > > Could you please send out any documentation around Async messenger ? I > tried to google it , but, not even blueprint is popping up. > > > > > > Thanks & Regards > > Somnath > > From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx] On Behalf > Of Haomai Wang > Sent: Monday, October 12, 2015 7:57 PM > To: Mark Nelson > Cc: ceph-devel; ceph-users@xxxxxxxxxxxxxx > Subject: Re: Initial performance cluster SimpleMessenger > vs AsyncMessenger results > > > > COOL > > > > Interesting that async messenger will consume more memory than simple, > in my mind I always think async should use less memory. I will give a > look at this > > > > On Tue, Oct 13, 2015 at 12:50 AM, Mark Nelson <mnelson@xxxxxxxxxx> wrote: > > Hi Guy, > > Given all of the recent data on how different memory allocator > configurations improve SimpleMessenger performance (and the effect of > memory allocators and transparent hugepages on RSS memory usage), I > thought I'd run some tests looking how AsyncMessenger does in > comparison. We spoke about these a bit at the last performance meeting but here's the full write up. > The rough conclusion as of right now appears to be: > > 1) AsyncMessenger performance is not dependent on the memory allocator > like with SimpleMessenger. > > 2) AsyncMessenger is faster than SimpleMessenger with TCMalloc + 32MB > (ie > default) thread cache. > > 3) AsyncMessenger is consistently faster than SimpleMessenger for 128K > random reads. > > 4) AsyncMessenger is sometimes slower than SimpleMessenger when memory > allocator optimizations are used. > > 5) AsyncMessenger currently uses far more RSS memory than SimpleMessenger. > > Here's a link to the paper: > > https://drive.google.com/file/d/0B2gTBZrkrnpZS1Q4VktjZkhrNHc/view > > Mark > _______________________________________________ > ceph-users mailing list > ceph-users@xxxxxxxxxxxxxx > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > > > > > -- > > Best Regards, > > Wheat > > > ________________________________ > > PLEASE NOTE: The information contained in this electronic mail message > is intended only for the use of the designated recipient(s) named > above. If the reader of this message is not the intended recipient, > you are hereby notified that you have received this message in error > and that any review, dissemination, distribution, or copying of this > message is strictly prohibited. If you have received this > communication in error, please notify the sender by telephone or > e-mail (as shown above) immediately and destroy any and all copies of > this message in your possession (whether hard copies or electronically stored copies). > -- Best Regards, Wheat ________________________________ PLEASE NOTE: The information contained in this electronic mail message is intended only for the use of the designated recipient(s) named above. If the reader of this message is not the intended recipient, you are hereby notified that you have received this message in error and that any review, dissemination, distribution, or copying of this message is strictly prohibited. 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