=?utf-8?q?Rados=C5=82aw_Smogura?= <rsmog...@softperience.eu> writes: > Tom Lane <t...@sss.pgh.pa.us> Sunday 17 April 2011 01:35:45 >> ... Huh? Are you saying that you ask the kernel to map each individual >> shared buffer separately? I can't believe that's going to scale to >> realistic applications.
> No, I do > mrempa(mmap_buff_A, MAP_FIXED, temp); > mremap(shared_buff_Y, MAP_FIXED, mmap_buff_A), > mrempa(tmp, MAP_FIXED, mmap_buff_A). There's no mremap() in the Single Unix Spec, nor on my ancient HPUX box, nor on my quite-up-to-date OS X box. The Linux man page for it says "This call is Linux-specific, and should not be used in programs intended to be portable." So if the patch is dependent on that call, it's dead on arrival from a portability standpoint. But in any case, you didn't explain how use of mremap() avoids the problem of the kernel having to maintain a separate page-mapping-table entry for each individual buffer. (Per process, yet.) If that's what's happening, it's going to be a significant performance penalty as well as (I suspect) a serious constraint on how many buffers can be managed. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers