On Mon, Sep 28, 2015 at 12:05 PM, Pavel Stehule <pavel.steh...@gmail.com> wrote:
> > 2015-09-28 12:01 GMT+02:00 Shulgin, Oleksandr < > oleksandr.shul...@zalando.de>: > >> On Sun, Sep 27, 2015 at 8:05 AM, Pavel Stehule <pavel.steh...@gmail.com> >> wrote: >> >> the preparing of content before execution is interesting idea, that can >>> be used more. The almost queries and plans are not too big, so when the >>> size of content is not too big - less than 1MB, then can be used one DSM >>> for all backends. >>> >> >> >>> When size of content is bigger than limit, then DSM will be allocated >>> specially for this content. The pointer to DSM and offset can be stored in >>> requested process slot. The reading and writing to requested slot should be >>> protected by spinlock, but it should block only two related processes for >>> short time (copy memory). >>> >> >> Sorry, I don't think this will fly. >> >> The whole idea is that a backend publishes the plan of a query just >> before running it and it doesn't care which other backend(s) might be >> reading it, how many times and in which order. The only required locking >> (implicit) is contained in the code for dsm_attach/detach(). >> > > I didn't propose too different solution. There is only one difference - > sharing DSM for smaller data. It is similar to using usual shared memory. > Does this mean implementing some sort of allocator on top of the shared memory segment? If so, how are you going to prevent fragmentation? -- Alex
