Re: Way to check whether a particular block is on the shared_buffer?

On Sun, Feb 7, 2016 at 9:49 PM, Kouhei Kaigai <kaigai@ak.jp.nec.com> wrote:
> On the other hands, it also became clear we have to guarantee OS buffer
> or storage block must not be updated partially during the P2P DMA.
> My motivation is a potential utilization of P2P DMA of SSD-to-GPU to
> filter out unnecessary rows and columns prior to loading to CPU/RAM.
> It needs to ensure PostgreSQL does not write out buffers to OS buffers
> to avoid unexpected data corruption.
>
> What I want to achieve is suspend of buffer write towards a particular
> (relnode, forknum, blocknum) pair for a short time, by completion of
> data processing by GPU (or other external devices).
> In addition, it is preferable being workable regardless of the choice
> of storage manager, even if we may have multiple options on top of the
> pluggable smgr in the future.

It seems like you just need to take an exclusive content lock on the
buffer, or maybe a shared content lock would be sufficient.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company