Re: WAL prefetch

On 06/27/2018 11:44 AM, Konstantin Knizhnik wrote:
> 
> ...
> 
> I have improved my WAL prefetch patch. The main reason of slowdown 
> recovery speed with enabled prefetch was that it doesn't take in account 
> initialized pages  (XLOG_HEAP_INIT_PAGE)
> and doesn't remember (cache) full page writes.
> The main differences of new version of the patch:
> 
> 1. Use effective_cache_size as size of cache of prefetched blocks
> 2. Do not prefetch blocks sent in shared buffers
> 3. Do not prefetch blocks  for RM_HEAP_ID with XLOG_HEAP_INIT_PAGE bit set
> 4. Remember new/fpw pages in prefetch cache, to avoid prefetch them for 
> subsequent  WAL records.
> 5. Add min/max prefetch lead parameters to make it possible to 
> synchronize speed of prefetch with speed of replay.
> 6. Increase size of open file cache to avoid redundant open/close 
> operations.
> 

Thanks. I plan to look at it and do some testing, but I won't have time 
until the end of next week (probably).

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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