Andres, Thanks for the reply!
I will try the ForwardFsyncRequest-like approach. 在 15-9-2 下午8:32， "Andres Freund" <and...@anarazel.de> 写入: >On 2015-09-10 19:39:59 +0800, 张广舟(明虚) wrote: >> We found there is a fsync call when CLOG buffer >> is written out in SlruPhysicalWritePage(). It is often called when a >>backend >> needs to check transaction status with SimpleLruReadPage(). > >That's when there's not enough buffers available some other, and your >case dirty, needs to be written out. > >You could try increasing the max (32) in CLOGShmemBuffers() further. > >> ctl->do_fsync is true for CLOG. Question is, could we just disable >>fsync >> for CLOG buffer write out here? Is it safe to do so? I understand a >> checkpoint will calls SimpleLruFlush to flush all CLOG buffer at once, >>and >> the fsync call here (for buffer write out) is not necessary. > >No, that'd not be safe. The reason we fsync in SlruPhysicalWritePage() >is that the flush during checkpoint won't necessarily touch those files >at all (as they've been replaced with other buffers in memory). > >This could be optimized though - it should be possible to delay the >fsync for slru files that have been evicted from memory till >checkpoint. Using something like ForwardFsyncRequest() except that it >obviously has to be usable for other files than normal relfilenodes. > >Greetings, > >Andres Freund -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
