On 01/15/2014 12:16 PM, Hannu Krosing wrote: > On 01/14/2014 06:12 PM, Robert Haas wrote: >> This would be pretty similar to copy-on-write, except >> without the copying. It would just be >> forget-from-the-buffer-pool-on-write. > +1 > > A version of this could probably already be implement using MADV_DONTNEED > and MADV_WILLNEED > > Thet is, just after reading the page in, use MADV_DONTNEED on it. When > evicting > a clean page, check that it is still in cache and if it is, then > MADV_WILLNEED it. > > Another nice thing to do would be dynamically adjusting kernel > dirty_background_ratio > and other related knobs in real time based on how many buffers are dirty > inside postgresql. > Maybe in background writer. > > Question to LKM folks - will kernel react well to frequent changes to > /proc/sys/vm/dirty_* ? > How frequent can they be (every few second? every second? 100Hz ?) One obvious use case of this would be changing dirty_background_bytes linearly to almost zero during a checkpoint to make final fsync fast.
Cheers -- Hannu Krosing PostgreSQL Consultant Performance, Scalability and High Availability 2ndQuadrant Nordic OÜ -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
